Johann Joseph on Geometrical-Optical Illusions: A Translation and Commentary.

Science.gov (United States)

Wade, Nicholas J; Todorović, Dejan; Phillips, David; Lingelbach, Bernd

2017-01-01

The term geometrical-optical illusions was coined by Johann Joseph Oppel (1815-1894) in 1855 in order to distinguish spatial distortions of size and orientation from the broader illusions of the senses. We present a translation of Oppel's article and a commentary on the material described in it. Oppel did much more than give a name to a class of visual spatial distortions. He examined a variety of figures and phenomena that were precursors of later, named illusions, and attempted to quantify and interpret them.

Involvement of the Extrageniculate System in the Perception of Optical Illusions: A Functional Magnetic Resonance Imaging Study.

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Tabei, Ken-Ichi; Satoh, Masayuki; Kida, Hirotaka; Kizaki, Moeni; Sakuma, Haruno; Sakuma, Hajime; Tomimoto, Hidekazu

2015-01-01

Research on the neural processing of optical illusions can provide clues for understanding the neural mechanisms underlying visual perception. Previous studies have shown that some visual areas contribute to the perception of optical illusions such as the Kanizsa triangle and Müller-Lyer figure; however, the neural mechanisms underlying the processing of these and other optical illusions have not been clearly identified. Using functional magnetic resonance imaging (fMRI), we determined which brain regions are active during the perception of optical illusions. For our study, we enrolled 18 participants. The illusory optical stimuli consisted of many kana letters, which are Japanese phonograms. During the shape task, participants stated aloud whether they perceived the shapes of two optical illusions as being the same or not. During the word task, participants read aloud the kana letters in the stimuli. A direct comparison between the shape and word tasks showed activation of the right inferior frontal gyrus, left medial frontal gyrus, and right pulvinar. It is well known that there are two visual pathways, the geniculate and extrageniculate systems, which belong to the higher-level and primary visual systems, respectively. The pulvinar belongs to the latter system, and the findings of the present study suggest that the extrageniculate system is involved in the cognitive processing of optical illusions.

Optical Illusions: Why You Should NOT Trust Your Eyes

Science.gov (United States)

Hockberger, Phil; Hockberger, Philip

2013-01-01

Digital image processing utilizes computer-aided enhancement to turn subjective features of an image into data that can be measured, quantified and evaluated. The first step in this process is deciding what features are of interest and tractable. This presentation will address how optical illusions distort and fabricate features due to fundamental properties of human visual perception. Examples of common illusions generated by microscope-based imaging systems will be described as well as ways in which to avoid or account for them.

Involvement of the Extrageniculate System in the Perception of Optical Illusions: A Functional Magnetic Resonance Imaging Study.

Directory of Open Access Journals (Sweden)

Ken-Ichi Tabei

Full Text Available Research on the neural processing of optical illusions can provide clues for understanding the neural mechanisms underlying visual perception. Previous studies have shown that some visual areas contribute to the perception of optical illusions such as the Kanizsa triangle and Müller-Lyer figure; however, the neural mechanisms underlying the processing of these and other optical illusions have not been clearly identified. Using functional magnetic resonance imaging (fMRI, we determined which brain regions are active during the perception of optical illusions. For our study, we enrolled 18 participants. The illusory optical stimuli consisted of many kana letters, which are Japanese phonograms. During the shape task, participants stated aloud whether they perceived the shapes of two optical illusions as being the same or not. During the word task, participants read aloud the kana letters in the stimuli. A direct comparison between the shape and word tasks showed activation of the right inferior frontal gyrus, left medial frontal gyrus, and right pulvinar. It is well known that there are two visual pathways, the geniculate and extrageniculate systems, which belong to the higher-level and primary visual systems, respectively. The pulvinar belongs to the latter system, and the findings of the present study suggest that the extrageniculate system is involved in the cognitive processing of optical illusions.

Johann Joseph Oppel (1855) on Geometrical–Optical Illusions: A Translation and Commentary

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Todorović, Dejan; Phillips, David; Lingelbach, Bernd

2017-01-01

The term geometrical–optical illusions was coined by Johann Joseph Oppel (1815–1894) in 1855 in order to distinguish spatial distortions of size and orientation from the broader illusions of the senses. We present a translation of Oppel’s article and a commentary on the material described in it. Oppel did much more than give a name to a class of visual spatial distortions. He examined a variety of figures and phenomena that were precursors of later, named illusions, and attempted to quantify and interpret them. PMID:28694957

Illusions.

Science.gov (United States)

Osterhaus, Kenneth

An art activity introduces intermediate grade and middle school students to optical illusions. Students practice drawing geometric shapes such as cubes, cylinders, cones, and pyramids, then combine these shapes to create the illusion of their choice. Graphic outlines for each shape are provided. This document is one of a collection of materials…

Uncertainty in visual processes predicts geometrical optical illusions.

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Fermüller, Cornelia; Malm, Henrik

2004-03-01

It is proposed in this paper that many geometrical optical illusions, as well as illusory patterns due to motion signals in line drawings, are due to the statistics of visual computations. The interpretation of image patterns is preceded by a step where image features such as lines, intersections of lines, or local image movement must be derived. However, there are many sources of noise or uncertainty in the formation and processing of images, and they cause problems in the estimation of these features; in particular, they cause bias. As a result, the locations of features are perceived erroneously and the appearance of the patterns is altered. The bias occurs with any visual processing of line features; under average conditions it is not large enough to be noticeable, but illusory patterns are such that the bias is highly pronounced. Thus, the broader message of this paper is that there is a general uncertainty principle which governs the workings of vision systems, and optical illusions are an artifact of this principle.

Illusion optics in chaotic light

International Nuclear Information System (INIS)

Zhang Suheng; Gan Shu; Xiong Jun; Zhang Xiangdong; Wang Kaige

2010-01-01

The time-reversal process provides the possibility to counteract the time evolution of a physical system. Recent research has shown that such a process can occur in the first-order field correlation of chaotic light and result in the spatial interference and phase-reversal diffraction in an unbalanced interferometer. Here we report experimental investigations on the invisibility cloak and illusion phenomena in chaotic light. In an unbalanced interferometer illuminated by thermal light, we have observed the cloak effect and the optical transformation of one object into another object. The experimental results can be understood by the phase-reversal diffraction, and they demonstrate the theoretical proposal of similar effects in complementary media.

Counter-rotating standing spin waves: A magneto-optical illusion

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Shihab, S.; Thevenard, L.; Lemaître, A.; Gourdon, C.

2017-04-01

We excite perpendicular standing spin waves by a laser pulse in a GaMnAsP ferromagnetic layer and detect them using time-resolved magneto-optical effects. Quite counterintuitively, we find the first two excited modes to be of opposite chirality. We show that this can only be explained by taking into account absorption and optical phase shift inside the layer. This optical illusion is particularly strong in weakly absorbing layers. These results provide a correct identification of spin waves modes, enabling a trustworthy estimation of their respective weight as well as an unambiguous determination of the spin stiffness parameter.

Size and direction of distortion in geometric-optical illusions: conciliation between the Müller-Lyer and Titchener configurations.

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Nemati, Farshad

2009-01-01

Over the past few decades, different theories have been advanced to explain geometric-optical illusions based on various perceptual processes such as assimilation and/or contrast. Consistent with the contradictory effects of assimilation and contrast, Pressey's assimilation theory provided an explanation for the Müller-Lyer illusion, but failed to account for the Titchener (Ebbinghaus) illusion. A model that explains both Müller-Lyer and Titchener illusions according to a common underlying process may outline a unified explanation for a variety of geometric-optical illusions. In order to develop such a model, the concept of empty space is introduced as an area of the illusory figure that is not filled by line drawings. It was predicted that the magnitude of illusion would increase with the area of the empty space around the illusory figures. The effect of empty space on the magnitude of perceptual distortion was measured in Müller-Lyer figures, with outward arrowheads of different length. The results indicated an overestimation of the target stimulus in all of the figures. Nevertheless, consistent with the prediction of the present model, the horizontal line in the Müller-Lyer figure with the longest arrowheads appeared shorter than that with the shortest arrowheads, although the size contrast of these figures was the same. According to the analysis proposed in the present study, the area of empty space not only affects the magnitude of illusion but also serves as a contextual cue for the perceptual system to determine the direction of illusion (orientation). The functional relationships between the size contrast and empty space provide a common explanation for the Müller-Lyer, Titchener, and a variety of other geometric-optical illusions.

Experimental demonstration of illusion optics with ``external cloaking'' effects

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Li, Chao; Liu, Xiao; Liu, Guochang; Li, Fang; Fang, Guangyou

2011-08-01

A metamaterial "illusion optics" with "complementary medium" and "restoring medium" is designed by using inductor-capacitor (L-C) network medium. The unprecedented effects of "external cloaking" and "transforming one object to appear as another" are demonstrated experimentally. We also demonstrate that the non-resonant nature of the L-C network decreases the sensitivity of the "external cloaking" effect to the variation of the frequency and results in an acceptable bandwidth of the whole device.

Overlapped illusion optics: a perfect lens brings a brighter feature

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Xu Yadong; Gao Lei; Chen Huanyang [School of Physical Science and Technology, Soochow University, Suzhou, Jiangsu 215006 (China); Du Shengwang, E-mail: kenyon@ust.hk [Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

2011-02-15

In this paper, we show that a perfect lens can be employed to make multiple objects appear like only one object in the far field, leading to a new concept in illusion optics. Numerical simulations have been performed to verify the functionalities for both passive and active objects. The conceptual device can be utilized to enhance the illumination brightness for both incoherent and coherent systems.

Overlapped illusion optics: a perfect lens brings a brighter feature

International Nuclear Information System (INIS)

Xu Yadong; Gao Lei; Chen Huanyang; Du Shengwang

2011-01-01

In this paper, we show that a perfect lens can be employed to make multiple objects appear like only one object in the far field, leading to a new concept in illusion optics. Numerical simulations have been performed to verify the functionalities for both passive and active objects. The conceptual device can be utilized to enhance the illumination brightness for both incoherent and coherent systems.

Application of Riesz transforms to the isotropic AM-PM decomposition of geometrical-optical illusion images.

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Sierra-Vázquez, Vicente; Serrano-Pedraza, Ignacio

2010-04-01

The existence of a special second-order mechanism in the human visual system, able to demodulate the envelope of visual stimuli, suggests that spatial information contained in the image envelope may be perceptually relevant. The Riesz transform, a natural isotropic extension of the Hilbert transform to multidimensional signals, was used here to demodulate band-pass filtered images of well-known visual illusions of length, size, direction, and shape. We show that the local amplitude of the monogenic signal or envelope of each illusion image conveys second-order information related to image holistic spatial structure, whereas the local phase component conveys information about the spatial features. Further low-pass filtering of the illusion image envelopes creates physical distortions that correspond to the subjective distortions perceived in the illusory images. Therefore the envelope seems to be the image component that physically carries the spatial information about these illusions. This result contradicts the popular belief that the relevant spatial information to perceive geometrical-optical illusions is conveyed only by the lower spatial frequencies present in their Fourier spectrum.

[Complex visual hallucinations following occipital infarct and perception of optical illusions].

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Renou, P; Deltour, S; Samson, Y

2008-05-01

The physiopathology of visual hallucinations in the hemianopic field secondary to occipital infarct is uncertain. We report the case of a patient with a history of occipital infarct who presented nonstereotyped complex hallucinations in the quadranopic field resulting from a second controlateral occipital infarct. Based on an experience with motion optical illusions, we suggested that the association of these two occipital lesions, involving the V5 motion area on the one side and the V1 area on the other side, could have produced the complex hallucinations due to a release phenomenon. The patient experienced simultaneously a double visual consciousness, with both hallucinations and real visual perceptions. The study of perceptual illusions in patients with visual hallucinations could illustrate the innovative theory of visual consciousness as being not unified but constituted of multiple microconsciousnesses.

Effects of high-frequency yoga breathing called kapalabhati compared with breath awareness on the degree of optical illusion perceived.

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Telles, Shirley; Maharana, Kanchan; Balrana, Budhi; Balkrishna, Acharya

2011-06-01

Prior research has shown that methods of meditation, breath control, and different kinds of yoga breathing affect attention and visual perception, including decreasing the size of certain optical illusions. Evaluating relationships sheds light on the perceptual and cognitive changes induced by yoga and related methods, and the locus of the effects. In the present study, the degree of optical illusion was assessed using Müller-Lyer stimuli before and immediately after two different kinds of practice, a high frequency yoga breathing called kapalabhati, and breath awareness. A nonyoga, control session tested for practice effects. Thirty participants (with group M age = 26.9 yr., SD = 5.7) practiced the two techniques for 18 min. on two separate days. The control group had 15 nonyoga practitioners assessed before and after 18 min. in which they did not perform any specific activity but were seated and relaxed. After both kapalabhati and breath awareness there was a significant decrease in the degree of optical illusion. The possibility that this was due to a practice or repetition effect was ruled out when 15 nonyoga practitioners showed no change in the degree of illusion when retested after 18 min. The changes were interpreted as due to changes in perception related to the way the stimuli were judged.

Influence of 'optical illusion' on the detectability of pneumothorax in diagnosis for chest CT images. Substantiation by visual psychological simulation images

International Nuclear Information System (INIS)

Henmi, Shuichi

2008-01-01

Some cases have been reported in which an optical illusion of lightness perception influences the detectability in diagnosis of low-density hematoma in head CT images in addition to the visual impression of the photographic density of the brain. Therefore, in this study, the author attempted to compare the detectability in diagnosis for chest images with pneumothorax using visual subjective evaluation, and investigated the influence of optical illusion on that detectability in diagnosis. Results indicated that in the window setting of lung, on such an occasion when the low-absorption free space with pneumothorax forms a crescent or the reduced lung borders on the chest-wall, an optical illusion in which the visual impression on the difference of the film contrast between the lung and the low-absorption free space with pneumothorax was psychologically emphasized when contrast was observed. In all cases the detectability in diagnosis for original images with the white thorax and mediastinum was superior to virtual images. Further, in case of the virtual double window setting of lung, thorax, and mediastinum, under the influence of the difference in the radiological anatomy of thorax and mediastinum as a result of the grouping theories of lightness computation, an optical illusion different from the original images was observed. (author)

Optical illusions and life-threatening traffic crashes: A perspective on aerial perspective.

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Redelmeier, Donald A; Raza, Sheharyar

2018-05-01

Aerial perspective illusion is a feature of visual perception where landscapes appear relatively close in clear light and distant in dim light. We hypothesized that bright sunlight might cause drivers to perceive distant terrain as relatively close and misinterpret the approach speed of surrounding landscape as unduly slow. This hypothesis would mean, in turn, that drivers in bright sunlight may underestimate their progress on the road, compensate by traveling at a faster baseline speed, and ultimately increase the prevailing risk of a life-threatening traffic crash. We conducted three pilot studies to illustrate how the illusion might contribute to a life- threatening traffic crash. The first illustration used a questionnaire to demonstrate that most respondents were mistaken when judging the distance between simple balls in different positions. The second illustration involved an experimental manipulation to assess whether aerial perspective influenced judgments about the relative positions of vehicles in traffic. The third illustration analyzed a segment of high-volume fast-speed traffic and found an increased frequency of speeding under bright sunlight. Together with past work based on the visual arts, these examples illustrate how an aerial perspective illusion can affect distance perception, may appear in realistic traffic situations, and could potentially contribute to the risk of a life-threatening traffic crash. An awareness of this hypothesis might lead to applications on how optical illusions could extend to everyday traffic and might potentially inform safety warnings to prevent life- threatening crashes. Copyright © 2018 Elsevier Ltd. All rights reserved.

Illusions and Cloaks for Surface Waves

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McManus, T. M.; Valiente-Kroon, J. A.; Horsley, S. A. R.; Hao, Y.

2014-08-01

Ever since the inception of Transformation Optics (TO), new and exciting ideas have been proposed in the field of electromagnetics and the theory has been modified to work in such fields as acoustics and thermodynamics. The most well-known application of this theory is to cloaking, but another equally intriguing application of TO is the idea of an illusion device. Here, we propose a general method to transform electromagnetic waves between two arbitrary surfaces. This allows a flat surface to reproduce the scattering behaviour of a curved surface and vice versa, thereby giving rise to perfect optical illusion and cloaking devices, respectively. The performance of the proposed devices is simulated using thin effective media with engineered material properties. The scattering of the curved surface is shown to be reproduced by its flat analogue (for illusions) and vice versa for cloaks.

The brain's dress code: How The Dress allows to decode the neuronal pathway of an optical illusion.

Science.gov (United States)

Schlaffke, Lara; Golisch, Anne; Haag, Lauren M; Lenz, Melanie; Heba, Stefanie; Lissek, Silke; Schmidt-Wilcke, Tobias; Eysel, Ulf T; Tegenthoff, Martin

2015-12-01

Optical illusions have broadened our understanding of the brain's role in visual perception. A modern day optical illusion emerged from a posted photo of a striped dress, which some perceived as white and gold and others as blue and black. Here we show, using functional magnetic resonance imaging (fMRI), that those who perceive The Dress as white/gold have higher activation in response to the image of The Dress in brain regions critically involved in higher cognition (frontal and parietal brain areas). These results are consistent with theories of top-down modulation and present a neural signature associated with the differences in perceiving The Dress as white/gold or blue/black. Furthermore the results support recent psychophysiological data on this phenomenon and provide a fundamental building block to study interindividual differences in visual processing. Copyright © 2015 Elsevier Ltd. All rights reserved.

Robotically enhanced rubber hand illusion.

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Arata, Jumpei; Hattori, Masashi; Ichikawa, Shohei; Sakaguchi, Masamichi

2014-01-01

The rubber hand illusion is a well-known multisensory illusion. In brief, watching a rubber hand being stroked by a paintbrush while one's own unseen hand is synchronously stroked causes the rubber hand to be attributed to one's own body and to "feel like it's my hand." The rubber hand illusion is thought to be triggered by the synchronized tactile stimulation of both the subject's hand and the fake hand. To extend the conventional rubber hand illusion, we introduce robotic technology in the form of a master-slave telemanipulator. The developed one degree-of-freedom master-slave system consists of an exoskeleton master equipped with an optical encoder that is worn on the subject's index finger and a motor-actuated index finger on the rubber hand, which allows the subject to perform unilateral telemanipulation. The moving rubber hand illusion has been studied by several researchers in the past with mechanically connected rigs between the subject's body and the fake limb. The robotic instruments let us investigate the moving rubber hand illusion with less constraints, thus behaving closer to the classic rubber hand illusion. In addition, the temporal delay between the body and the fake limb can be precisely manipulated. The experimental results revealed that the robotic instruments significantly enhance the rubber hand illusion. The time delay is significantly correlated with the effect of the multisensory illusion, and the effect significantly decreased at time delays over 100 ms. These findings can potentially contribute to the investigations of neural mechanisms in the field of neuroscience and of master-slave systems in the field of robotics.

Computer Generated Optical Illusions: A Teaching and Research Tool.

Science.gov (United States)

Bailey, Bruce; Harman, Wade

Interactive computer-generated simulations that highlight psychological principles were investigated in this study in which 33 female and 19 male undergraduate college student volunteers of median age 21 matched line and circle sizes in six variations of Ponzo's illusion. Prior to working with the illusions, data were collected based on subjects'…

dc illusion and its experimental verification

Science.gov (United States)

Liu, Min; Lei Mei, Zhong; Ma, Xiang; Cui, Tie Jun

2012-07-01

Based on the transformation optics method, we propose a dc illusion device, which can transform a metallic object into a magnified dielectric object using anisotropic conducting materials. Utilizing the analogy between electric conductivities and resistor networks, we design and fabricate the device using metal film resistors. The practical measurement data agree very well with simulation results. The proposed dc illusion device is easy to process and measure, and thus has potential applications in various sectors.

P1-19: Horizontal Vertical Illusion by Touch

Directory of Open Access Journals (Sweden)

Yoshinari Kinoshita

2012-10-01

Full Text Available Revesz (1934 Zeitschrift fur PsychologieBd. 1, Kap 20 and Bean (1938 Journal of Experimental Psychology 22 283–289. reported almost all the geometrical optical illusions existed in a tactual mode. Such a study can examine theories of visual illusions with modality-free theories. A number of articles have been devoted to the theory that repeated judgments decline the magnitude of visual illusion. In the current study, we examine whether repeated judgments decline the magnitude of geometrical haptic illusion. The Fick illusion (i.e., a horizontal vertical illusion was investigated. A graphics Braille display with 32×48 dots was used to present an inverted T haptically without vision. The horizontal line was consistently 49.2 mm long, and the vertical line was varied in each trial. Three subjects with normal sight participated. They judged which line was longer than the other. The point of subjective equality at which the subject perceives the two lines to be the same was measured using the method of constant stimuli. In the first session the mean PSE was about 13%; to compensate for the illusion, the vertical line must be set physically shorter than the horizontal line. We found that repeated judgments produced a reduction in illusion magnitude and dissolved the illusion entirely.

Hiding objects and creating illusions above a carpet filter using a Fourier optics approach.

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Wu, Kedi; Wang, Guo Ping

2010-09-13

Invisibility carpet cloaks are usually used to hide an object beneath carpet. In this paper we propose and demonstrate a carpet filter to hide objects and create illusions above the filter by using a Fourier optics method. Instead of using transformation optics, we get electromagnetic parameters of the filter by optical transfer functions, which play the role of modulating the propagation of the scattering angular spectrum directly from an object above the filter. By further adding a functional layer onto the filter, we can even camouflage the object so that it appears to be a different object. The analytical results are confirmed by numerical simulations. Our method is completely different from the current coordinate transfer method and may provide another point of view to more clearly understand the mechanism of invisibility cloaks.

Robust size illusion produced by expanding and contracting flow fields.

Science.gov (United States)

Dong, Xue; Bai, Jianying; Bao, Min

2017-04-01

A new illusion is described. Randomly positioned dots moved radially within an imaginary annular window. The dots' motion periodically changed the direction, leading to an alternating percept of expanding and contracting motion. Strikingly, the apparent size of the enclosed circular region shrank during the dots' expanding phases and dilated during the contracting phases. We quantitatively measured the illusion, and found that the presence of energy at the local kinetic edge could not account for the illusion. Besides, we reproduced the illusion on a natural scene background seen from a first-person point of view that moved forward and backward periodically. Blurring the boundaries of motion areas could not reverse the illusion in all subjects. Taken together, our observed illusion is likely induced by optic flow processing with some components of motion contrast. Expanding or contracting dots may induce the self-motion perception of either approaching or leaving way from the circle. These will make the circle appear smaller or larger since its retinal size remains constant. Copyright © 2017 Elsevier Ltd. All rights reserved.

Geometrical optical illusionists.

Science.gov (United States)

Wade, Nicholas J

2014-01-01

Geometrical optical illusions were given this title by Oppel in 1855. Variants on such small distortions of visual space were illustrated thereafter, many of which bear the names of those who first described them. Some original forms of the geometrical optical illusions are shown together with 'perceptual portraits' of those who described them. These include: Roget, Chevreul, Fick, Zöllner, Poggendorff, Hering, Kundt, Delboeuf Mach, Helmholtz, Hermann, von Bezold, Müller-Lyer, Lipps, Thiéry, Wundt, Münsterberg, Ebbinghaus, Titchener, Ponzo, Luckiesh, Sander, Ehrenstein, Gregory, Heard, White, Shepard, and. Lingelbach. The illusions are grouped under the headings of orientation, size, the combination of size and orientation, and contrast. Early theories of illusions, before geometrical optical illusions were so named, are mentioned briefly.

Comparative fiscal illusion: A fiscal illusion index for the European Union

OpenAIRE

Dell'Anno, Roberto; Dollery, Brian

2012-01-01

This paper provides an empirical analysis of fiscal illusion by estimating an index of fiscal illusion for 28 European countries over the period 1995–2008 employing a structural equation approach. Using MIMIC models, the paper investigates the main indicators of fiscal illusion and develops an index of fiscal illusion. It concludes that the chief deterninants for the deployment of fiscal illusion strategies are the share of self-employment on total employment, the educational level of citizen...

Illusions of causality: how they bias our everyday thinking and how they could be reduced.

Science.gov (United States)

Matute, Helena; Blanco, Fernando; Yarritu, Ion; Díaz-Lago, Marcos; Vadillo, Miguel A; Barberia, Itxaso

2015-01-01

Illusions of causality occur when people develop the belief that there is a causal connection between two events that are actually unrelated. Such illusions have been proposed to underlie pseudoscience and superstitious thinking, sometimes leading to disastrous consequences in relation to critical life areas, such as health, finances, and wellbeing. Like optical illusions, they can occur for anyone under well-known conditions. Scientific thinking is the best possible safeguard against them, but it does not come intuitively and needs to be taught. Teaching how to think scientifically should benefit from better understanding of the illusion of causality. In this article, we review experiments that our group has conducted on the illusion of causality during the last 20 years. We discuss how research on the illusion of causality can contribute to the teaching of scientific thinking and how scientific thinking can reduce illusion.

Perception, Illusion, and Magic.

Science.gov (United States)

Solomon, Paul R.

1980-01-01

Describes a psychology course in which magical illusions were used for teaching the principles of sensation and perception. Students read psychological, philosophical, historical, and magical literature on illusion, performed a magical illusion, and analyzed the illusion in terms of the psychological principles involved. (Author/KC)

Illusions of causality: How they bias our everyday thinking and how they could be reduced

Directory of Open Access Journals (Sweden)

Helena eMatute

2015-07-01

Full Text Available Illusions of causality occur when people develop the belief that there is a causal connection between two events that are actually unrelated. Such illusions have been proposed to underlie pseudoscience and superstitious thinking, sometimes leading to disastrous consequences in relation to critical life areas, such as health, finances, and wellbeing. Like optical illusions, they can occur for anyone under well-known conditions. Scientific thinking is the best possible safeguard against them, but it does not come intuitively and needs to be taught. Teaching how to think scientifically should benefit from better understanding of the illusion of causality. In this article, we review experiments that our group has conducted on the illusion of causality during the last 20 years. We discuss how research on the illusion of causality can contribute to the teaching of scientific thinking and how scientific thinking can reduce illusion.

Illusions of causality: how they bias our everyday thinking and how they could be reduced

Science.gov (United States)

Matute, Helena; Blanco, Fernando; Yarritu, Ion; Díaz-Lago, Marcos; Vadillo, Miguel A.; Barberia, Itxaso

2015-01-01

Illusions of causality occur when people develop the belief that there is a causal connection between two events that are actually unrelated. Such illusions have been proposed to underlie pseudoscience and superstitious thinking, sometimes leading to disastrous consequences in relation to critical life areas, such as health, finances, and wellbeing. Like optical illusions, they can occur for anyone under well-known conditions. Scientific thinking is the best possible safeguard against them, but it does not come intuitively and needs to be taught. Teaching how to think scientifically should benefit from better understanding of the illusion of causality. In this article, we review experiments that our group has conducted on the illusion of causality during the last 20 years. We discuss how research on the illusion of causality can contribute to the teaching of scientific thinking and how scientific thinking can reduce illusion. PMID:26191014

On the aesthetic illusion.

Science.gov (United States)

Balter, L

1999-01-01

The aesthetic illusion--the experience of the content of a work of art as reality--occurs through the mobilization and intensification of typical infantile fantasies in the beholder. This necessarily evokes intrapsychic conflict in the mature adult. Two illusion-producing strategies ameliorate this conflict and effect the aesthetic illusion. The first illusion is that the artist's proffered fantasy is the beholder's own personal and private fantasy. This isolates the beholder from the shame- and guilt-evoking social surround. The second illusion is that the protagonist depicted in the work is an actual person. This defends the beholder from the painful emotions attendant upon his instinctually gratifying identification with the protagonist. The first illusion is necessary for the establishment of the second, but it is the second that establishes the aesthetic illusion. The aesthetic illusion exists in a highly unstable dynamic equilibrium with the beholder's usual reality orientation. If either orientation is too powerful, the dynamic equilibrium is disrupted and the aesthetic experience as such is abolished.

Negative polarity illusions and the format of hierarchical encodings in memory.

Science.gov (United States)

Parker, Dan; Phillips, Colin

2016-12-01

Linguistic illusions have provided valuable insights into how we mentally navigate complex representations in memory during language comprehension. Two notable cases involve illusory licensing of agreement and negative polarity items (NPIs), where comprehenders fleetingly accept sentences with unlicensed agreement or an unlicensed NPI, but judge those same sentences as unacceptable after more reflection. Existing accounts have argued that illusions are a consequence of faulty memory access processes, and make the additional assumption that the encoding of the sentence remains fixed over time. This paper challenges the predictions made by these accounts, which assume that illusions should generalize to a broader set of structural environments and a wider range of syntactic and semantic phenomena. We show across seven reading-time and acceptability judgment experiments that NPI illusions can be reliably switched "on" and "off", depending on the amount of time from when the potential licensor is processed until the NPI is encountered. But we also find that the same profile does not extend to agreement illusions. This contrast suggests that the mechanisms responsible for switching the NPI illusion on and off are not shared across all illusions. We argue that the contrast reflects changes over time in the encoding of the semantic/pragmatic representations that can license NPIs. Just as optical illusions have been informative about the visual system, selective linguistic illusions are informative not only about the nature of the access mechanisms, but also about the nature of the encoding mechanisms. Copyright © 2016 Elsevier B.V. All rights reserved.

Anti-optic-null medium: Achieving the optic-null medium effect by enclosing an air region with relatively low-anisotropy media

Science.gov (United States)

Sun, Fei; Liu, Yichao; He, Sailing

2016-07-01

A so-called anti-optic-null medium (anti-ONM), which can be utilized to cancel the optic-null medium (ONM) and create many novel optical illusions, is introduced and designed by transformation optics (TO). Optical separation illusions can be achieved with an anti-ONM. With the help of the anti-ONM, we can achieve the same optical illusions where ONM is required via a shelled structure filled with low anisotropic medium, which is easier to realize for some novel optical devices designed by TO and optical surface transformation. The special function of the anti-ONM will lead to a new way to design optical devices or simplify the material requirements. Overlapping illusions, and wave-front reshapers are designed to demonstrate the function of the proposed method.

Spatial limits on the nonvisual self-touch illusion and the visual rubber hand illusion: subjective experience of the illusion and proprioceptive drift.

Science.gov (United States)

Aimola Davies, Anne M; White, Rebekah C; Davies, Martin

2013-06-01

The nonvisual self-touch rubber hand paradigm elicits the compelling illusion that one is touching one's own hand even though the two hands are not in contact. In four experiments, we investigated spatial limits of distance (15 cm, 30 cm, 45 cm, 60 cm) and alignment (0°, 90° anti-clockwise) on the nonvisual self-touch illusion and the well-known visual rubber hand illusion. Common procedures (synchronous and asynchronous stimulation administered for 60s with the prosthetic hand at body midline) and common assessment methods were used. Subjective experience of the illusion was assessed by agreement ratings for statements on a questionnaire and time of illusion onset. The nonvisual self-touch illusion was diminished though never abolished by distance and alignment manipulations, whereas the visual rubber hand illusion was more robust against these manipulations. We assessed proprioceptive drift, and implications of a double dissociation between subjective experience of the illusion and proprioceptive drift are discussed. Copyright © 2013 Elsevier Inc. All rights reserved.

PERFECT DEMAND ILLUSION

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Alexander Yu. Sulimov

2015-01-01

Full Text Available The article is devoted to technique «Perfect demand illusion», which allows to strengthen the competitive advantageof retailers. Also in the paper spells out the golden rules of visual merchandising.The definition of the method «Demand illusion», formulated the conditions of its functioning, and is determined by the mainhypothesis of the existence of this method.Furthermore, given the definition of the «Perfect demand illusion», and describes its additional conditions. Also spells out the advantages of the «Perfect demandillusion», before the «Demand illusion».

Tuning self-motion perception in virtual reality with visual illusions.

Science.gov (United States)

Bruder, Gerd; Steinicke, Frank; Wieland, Phil; Lappe, Markus

2012-07-01

Motion perception in immersive virtual environments significantly differs from the real world. For example, previous work has shown that users tend to underestimate travel distances in virtual environments (VEs). As a solution to this problem, researchers proposed to scale the mapped virtual camera motion relative to the tracked real-world movement of a user until real and virtual motion are perceived as equal, i.e., real-world movements could be mapped with a larger gain to the VE in order to compensate for the underestimation. However, introducing discrepancies between real and virtual motion can become a problem, in particular, due to misalignments of both worlds and distorted space cognition. In this paper, we describe a different approach that introduces apparent self-motion illusions by manipulating optic flow fields during movements in VEs. These manipulations can affect self-motion perception in VEs, but omit a quantitative discrepancy between real and virtual motions. In particular, we consider to which regions of the virtual view these apparent self-motion illusions can be applied, i.e., the ground plane or peripheral vision. Therefore, we introduce four illusions and show in experiments that optic flow manipulation can significantly affect users' self-motion judgments. Furthermore, we show that with such manipulations of optic flow fields the underestimation of travel distances can be compensated.

Optical illusions in scanning electron micrographs: the case of the eggshell of Acrosternum (Chinavia) marginatum (Hemiptera: Pentatomidae).

Science.gov (United States)

Wolf, Klaus W; Reid, Walton; Schrauf, Michael

2003-01-01

Scanning electron microscopy revealed that-as is common in this family of the Hemiptera-the eggs of the green stink bug Acrosternum (Chinavia) marginatum are roughly barrel-shaped and possess at their apical pole a row of slender extensions, the aero-micropylar processes. The outer surface of the eggshell carries hexagonally arranged pits. The analysis of cross-fractured eggshells showed that the pits have slender basal extensions with transverse diaphragms. When scanning electron micrographs of the egg surface of A. marginatum are viewed upside down, the perception flips and the pits appear as elevations to all observers addressed. Thus, we are dealing with an optical illusion, which is known as the 'shape-from-shading effect'. The perceived dents remain robust to changes in the angle of recording (zero to ca. 60 degrees tilt), the magnification (ca. x100 to x1400), and the number of pits included in the micrograph (one to several hundred). When through appropriate positioning of the specimen under the electron beam, contrast is significantly reduced and the distinct shadows at the slope of the pits are eliminated, the optical illusion does not appear. It is inferred that shades provide the decisive clue that determines whether bumps or dents will be perceived. Owing to the low resolution of their compound eyes, the shape-from-shading effect on the eggshell of the bug is in all likelihood not perceived by insects.

Analysis on an illusion unexpected occurred on a moving statue leaving in fact but approaching by environmental judgment

Science.gov (United States)

He, Youwu; Li, Zhifang; Qiu, Yishen; Li, Hui

2017-08-01

Earlier this year we visited Sanya, Hainan Province, China. There is a huge statue, the South Sea Avalokitesvara (南海观世音菩萨), at Sanya Nanshan Buddhism Cultural Tourism Resort. When we were gazing at the statue on a leaving car on gradually rising road, an unexpected visual illusion took place in which the statue seemed running after us. In this presentation, an optical model is developed to explain the illusion occurred on a moving object leaving in fact but approaching by environmental judgement. Such an interesting illusion analysis will play a significant role in having students understood the main principles in geometrical optics.

Visually induced reorientation illusions

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Howard, I. P.; Hu, G.; Oman, C. M. (Principal Investigator)

2001-01-01

It is known that rotation of a furnished room around the roll axis of erect subjects produces an illusion of 360 degrees self-rotation in many subjects. Exposure of erect subjects to stationary tilted visual frames or rooms produces only up to 20 degrees of illusory tilt. But, in studies using static tilted rooms, subjects remained erect and the body axis was not aligned with the room. We have revealed a new class of disorientation illusions that occur in many subjects when placed in a 90 degrees or 180 degrees tilted room containing polarised objects (familiar objects with tops and bottoms). For example, supine subjects looking up at a wall of the room feel upright in an upright room and their arms feel weightless when held out from the body. We call this the levitation illusion. We measured the incidence of 90 degrees or 180 degrees reorientation illusions in erect, supine, recumbent, and inverted subjects in a room tilted 90 degrees or 180 degrees. We report that reorientation illusions depend on the displacement of the visual scene rather than of the body. However, illusions are most likely to occur when the visual and body axes are congruent. When the axes are congruent, illusions are least likely to occur when subjects are prone rather than supine, recumbent, or inverted.

The discoloration illusion.

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Pinna, Baingio

2006-01-01

The discoloration illusion, a new visual phenomenon, is described. This phenomenon originates from the juxtaposition of eight chromatic parallel contours on a white background, creating a luminance gradient and enclosing a light red region. Under these conditions, the inner region appears white: the light red discolors and appears white with both surface color and luminous qualities. In two experiments, the discoloration illusion was (i) compared with the coloration effect of the watercolor illusion, obtained when the number of adjacent contours was reduced to at least two, and (ii) tested under several conditions useful for understanding the roles of the luminance gradient profile. The results suggest that discoloration is not a lightness illusion and does not depend on simultaneous contrast or on achromatic mechanisms, but more likely on chromatic mechanisms that, through the luminance chromatic gradient, provide cues about the interactions of light and surface and model the volume by depicting lights and shades. The discoloration illusion suggests a possible neural scenario where multiple juxtaposed contours may stimulate neurons, selective for different asymmetric luminance profiles and signaling not only the unilateral belongingness of the boundaries and the coloration effect but also the volumetric and the illumination effects.

Marvels of illusion: illusion and perception in the art of Salvador Dali.

Science.gov (United States)

Martinez-Conde, Susana; Conley, Dave; Hine, Hank; Kropf, Joan; Tush, Peter; Ayala, Andrea; Macknik, Stephen L

2015-01-01

The surrealist movement aimed to blur the distinction between the real and the imagined. Such lack of a border between demonstrable truth and fantasy is perhaps most apparent in the art of Spanish painter Salvador Dali (1904-1989). Dali included numerous illusions in his artworks, with the intent to challenge the viewers' perceptions of reality and to enable them to see beyond the surface. The "Marvels of Illusion" exhibit, shown at The Dali Museum in St. Petersburg, FL., from June 14 to October 12, 2014, showcased Dali paintings, prints and sculptures centered on illusory themes. Here, we review the significance of illusions in Dali's art, focusing on the pieces displayed at the "Marvels of Illusion" exhibit.

Body Schema Illusions: A Study of the Link between the Rubber Hand and Kinesthetic Mirror Illusions through Individual Differences.

Science.gov (United States)

Metral, Morgane; Gonthier, Corentin; Luyat, Marion; Guerraz, Michel

2017-01-01

The well-known rubber hand paradigm induces an illusion by having participants feel the touch applied to a fake hand. In parallel, the kinesthetic mirror illusion elicits illusions of movement by moving the reflection of a participant's arm. Experimental manipulation of sensory inputs leads to emergence of these multisensory illusions. There are strong conceptual similarities between these two illusions, suggesting that they rely on the same neurophysiological mechanisms, but this relationship has never been investigated. Studies indicate that participants differ in their sensitivity to these illusions, which provides a possibility for studying the relationship between these two illusions. We tested 36 healthy participants to confirm that there exist reliable individual differences in sensitivity to the two illusions and that participants sensitive to one illusion are also sensitive to the other. The results revealed that illusion sensitivity was very stable across trials and that individual differences in sensitivity to the kinesthetic mirror illusion were highly related to individual differences in sensitivity to the rubber hand illusion. Overall, these results support the idea that these two illusions may be both linked to a transitory modification of body schema, wherein the most sensitive people have the most malleable body schema.

Money illusion and coordination failure

DEFF Research Database (Denmark)

Fehr, Ernst; Tyran, Jean-Robert

2007-01-01

Economists long considered money illusion to be largely irrelevant. Here we show, however, that money illusion has powerful effects on equilibrium selection. If we represent payoffs in nominal terms, choices converge to the Pareto inferior equilibrium; however, if we lift the veil of money...... by representing payoffs in real terms, the Pareto efficient equilibrium is selected. We also show that strategic uncertainty about the other players' behavior is key for the equilibrium selection effects of money illusion: even though money illusion vanishes over time if subjects are given learning opportunities...... in the context of an individual optimization problem, powerful and persistent effects of money illusion are found when strategic uncertainty prevails...

Body Schema Illusions: A Study of the Link between the Rubber Hand and Kinesthetic Mirror Illusions through Individual Differences

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Morgane Metral

2017-01-01

Full Text Available Background. The well-known rubber hand paradigm induces an illusion by having participants feel the touch applied to a fake hand. In parallel, the kinesthetic mirror illusion elicits illusions of movement by moving the reflection of a participant’s arm. Experimental manipulation of sensory inputs leads to emergence of these multisensory illusions. There are strong conceptual similarities between these two illusions, suggesting that they rely on the same neurophysiological mechanisms, but this relationship has never been investigated. Studies indicate that participants differ in their sensitivity to these illusions, which provides a possibility for studying the relationship between these two illusions. Method. We tested 36 healthy participants to confirm that there exist reliable individual differences in sensitivity to the two illusions and that participants sensitive to one illusion are also sensitive to the other. Results. The results revealed that illusion sensitivity was very stable across trials and that individual differences in sensitivity to the kinesthetic mirror illusion were highly related to individual differences in sensitivity to the rubber hand illusion. Conclusions. Overall, these results support the idea that these two illusions may be both linked to a transitory modification of body schema, wherein the most sensitive people have the most malleable body schema.

Marvels of Illusion: illusion and perception in the art of Salvador Dali

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Susana eMartinez-Conde

2015-09-01

Full Text Available The surrealist movement aimed to blur the distinction between the real and the imagined. Such lack of a border between demonstrable truth and fantasy is perhaps most apparent in the art of Spanish painter Salvador Dali (1904-1989. Dali included numerous illusions in his artworks, with the intent to challenge the viewers’ perceptions of reality and to enable them to see beyond the surface. The Marvels of Illusion exhibit, shown at The Dali Museum in St. Petersburg, FL., from June 14 to October 12, 2014, showcased Dali paintings, prints and sculptures centered on illusory themes. Here we review the significance of illusions in Dali’s art, focusing on the pieces displayed at the Marvels of Illusion exhibit.

Experiments on Active Cloaking and Illusion for Laplace Equation

Science.gov (United States)

Ma, Qian; Mei, Zhong Lei; Zhu, Shou Kui; Jin, Tian Yu; Cui, Tie Jun

2013-10-01

In recent years, invisibility cloaks have received a lot of attention and interest. These devices are generally classified into two types: passive and active. The design and realization of passive cloaks have been intensively studied using transformation optics and plasmonic approaches. However, active cloaks are still limited to theory and numerical simulations. Here, we present the first experiment on active cloaking and propose an active illusion for the Laplace equation. We make use of a resistor network to simulate a conducting medium. Then, we surround the central region with controlled sources to protect it from outside detection. We show that by dynamically changing the controlled sources, the protected region can be cloaked or disguised as different objects (illusion). Our measurement results agree very well with numerical simulations. Compared with the passive counterparts, the active cloaking and illusion devices do not need complicated metamaterials. They are flexible, in-line controllable, and adaptable to the environment. In addition to dc electricity, the proposed method can also be used for thermodynamics and other problems governed by the Laplace equation.

Magic and the aesthetic illusion.

Science.gov (United States)

Balter, Leon

2002-01-01

The aesthetic illusion is the subjective experience that the content of a work of art is reality. It has an intrinsic relation to magic, an intrapsychic maneuver oriented toward modification and control of the extraspyschic world, principally through ego functioning. Magic is ontogenetically and culturally archaic, expresses the omnipotence inherent in primary narcissism, and operates according to the logic of the primary process. Magic is a constituent of all ego functioning, usually latent in later development. It may persist as an archaic feature or may be evoked regressively in global or circumscribed ways. It causes a general disinhibition of instincts and impulses attended by a sense of confidence, exhiliration, and exuberance. The aesthetic illusion is a combination of illusions: (1) that the daydream embodied by the work of art is the beholder's own, the artist being ignored, and (2) that the artistically described protagonist is a real person with a real "world." The first illusion arises through the beholder's emotional-instinctual gratification from his or her own fantasy-memory constellations; the second comes about because the beholder, by taking the protagonist as proxy, mobilizes the subjective experience of the imaginary protagonist's "reality." The first illusion is necessary for the second to take place; the second establishes the aesthetic illusion proper. Both illusions are instances of magic. Accordingly, the aesthetic illusion is accompanied by a heady experience of excitement and euphoria. The relation among the aesthetic illusion, magic, and enthusiasm is illustrated by an analytic case, J. D. Salinger's "The Laughing Man," Woody Allen's Play It Again, Sam, Don Quixote, and the medieval Cult of the Saints.

Transformation magneto-statics and illusions for magnets

Science.gov (United States)

Sun, Fei; He, Sailing

2014-10-01

Based on the form-invariant of Maxwell's equations under coordinate transformations, we extend the theory of transformation optics to transformation magneto-statics, which can design magnets through coordinate transformations. Some novel DC magnetic field illusions created by magnets (e.g. rescaling magnets, cancelling magnets and overlapping magnets) are designed and verified by numerical simulations. Our research will open a new door to designing magnets and controlling DC magnetic fields.

Directed Thermal Diffusions through Metamaterial Source Illusion with Homogeneous Natural Media

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Guoqiang Xu

2018-04-01

Full Text Available Owing to the utilization of transformation optics, many significant research and development achievements have expanded the applications of illusion devices into thermal fields. However, most of the current studies on relevant thermal illusions used to reshape the thermal fields are dependent of certain pre-designed geometric profiles with complicated conductivity configurations. In this paper, we propose a methodology for designing a new class of thermal source illusion devices for achieving directed thermal diffusions with natural homogeneous media. The employments of the space rotations in the linear transformation processes allow the directed thermal diffusions to be independent of the geometric profiles, and the utilization of natural homogeneous media improve the feasibility. Four schemes, with fewer types of homogeneous media filling the functional regions, are demonstrated in transient states. The expected performances are observed in each scheme. The related performance are analyzed by comparing the thermal distribution characteristics and the illusion effectiveness on the measured lines. The findings obtained in this paper see applications in the development of directed diffusions with minimal thermal loss, used in novel “multi-beam” thermal generation, thermal lenses, solar receivers, and waveguide.

Motion illusions in optical art presented for long durations are temporally distorted.

Science.gov (United States)

Nather, Francisco Carlos; Mecca, Fernando Figueiredo; Bueno, José Lino Oliveira

2013-01-01

Static figurative images implying human body movements observed for shorter and longer durations affect the perception of time. This study examined whether images of static geometric shapes would affect the perception of time. Undergraduate participants observed two Optical Art paintings by Bridget Riley for 9 or 36 s (group G9 and G36, respectively). Paintings implying different intensities of movement (2.0 and 6.0 point stimuli) were randomly presented. The prospective paradigm in the reproduction method was used to record time estimations. Data analysis did not show time distortions in the G9 group. In the G36 group the paintings were differently perceived: that for the 2.0 point one are estimated to be shorter than that for the 6.0 point one. Also for G36, the 2.0 point painting was underestimated in comparison with the actual time of exposure. Motion illusions in static images affected time estimation according to the attention given to the complexity of movement by the observer, probably leading to changes in the storage velocity of internal clock pulses.

Sensory illusions: Common mistakes in physics regarding sound, light and radio waves

Science.gov (United States)

Briles, T. M.; Tabor-Morris, A. E.

2013-03-01

Optical illusions are well known as effects that we see that are not representative of reality. Sensory illusions are similar but can involve other senses than sight, such as hearing or touch. One mistake commonly noted among instructors is that students often mis-identify radio signals as sound waves and not as part of the electromagnetic spectrum. A survey of physics students from multiple high schools highlights the frequency of this common misconception, as well as other nuances on this misunderstanding. Many students appear to conclude that, since they experience radio broadcasts as sound, then sound waves are the actual transmission of radio signals and not, as is actually true, a representation of those waves as produced by the translator box, the radio. Steps to help students identify and correct sensory illusion misconceptions are discussed. School of Education

Do Dogs See the Ponzo illusion?

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Sarah-Elizabeth Byosiere

2017-10-01

Full Text Available While domestic dogs (Canis familiaris play a large role in human daily lives, little is known about how they perceive the visual world. Recent research suggests that dogs may perceive certain visual illusions differently than humans. To further evaluate geometric illusion susceptibility, eight dogs were assessed on their susceptibility to the Ponzo illusion. Four experiments were conducted: 1 a presentation of the Ponzo illusion with target circles in a ‘grid inducer context’, 2 a re-test of Experiment 1 after additional training, 3 a presentation of the Ponzo illusion with target rectangles in a ‘grid inducer context’ and 4 a presentation of the Ponzo illusion with target circles in a ‘converging lines context.’ A one-sample t-test of the dogs’ responses to the Ponzo stimuli in Experiment 1 demonstrated illusion susceptibility at the group level; however, no individual dog performed significantly above chance in binomial tests. In Experiments 2, 3, and 4, one-sample t-tests found no significant results at the group level, although one or more dogs did demonstrate a small but significant effect. Taken together, then, there was limited evidence for dogs’ susceptibility to the Ponzo illusion in a two-choice discrimination paradigm. As most animals tested previously have demonstrated human-like susceptibility to the Ponzo illusion, these findings have implications for theoretical explanations. The divergence of results between dogs and humans/other animals suggest that mechanisms underlying perception of the Ponzo illusion may differ across species and that care should be taken when using visual paradigms to test dogs’ cognitive skills.

Theoretical parallels between the Ponzo illusion and the Wundt-Jastrow illusion.

Science.gov (United States)

Pick, D F; Pierce, K A

1993-04-01

Misapplied-size-constancy, assimilation, and contrast theories are discussed as explanations for the Wundt-Jastrow and Ponzo illusions. An experiment is reported that questions the need to include a contrast function in the assimilation theory of Pressey and Wilson to account for the Wundt-Jastrow illusion. Several directions for further research are proposed.

The Star Wars Scroll Illusion.

Science.gov (United States)

Shapiro, Arthur G

2015-10-01

The Star Wars Scroll Illusion is a dynamic version of the Leaning Tower Illusion. When two copies of a Star-Wars-like scrolling text are placed side by side (with separate vanishing points), the two scrolls appear to head in different directions even though they are physically parallel in the picture plane. Variations of the illusion are shown with one vanishing point, as well as from an inverted perspective where the scrolls appear to originate in the distance. The demos highlight the conflict between the physical lines in the picture plane and perspective interpretation: With two perspective points, the scrolling texts are parallel to each other in the picture plane but not in perspective interpretation; with one perspective point, the texts are not parallel to each other in the picture plane but are parallel to each other in perspective interpretation. The size of the effect is linearly related to the angle of rotation of the scrolls into the third dimension; the Scroll Illusion is stronger than the Leaning Tower Illusion for rotation angles between 35° and 90°. There is no effect of motion per se on the strength of the illusion.

The Star Wars Scroll Illusion

Directory of Open Access Journals (Sweden)

Arthur G. Shapiro

2015-09-01

Full Text Available The Star Wars Scroll Illusion is a dynamic version of the Leaning Tower Illusion. When two copies of a Star-Wars-like scrolling text are placed side by side (with separate vanishing points, the two scrolls appear to head in different directions even though they are physically parallel in the picture plane. Variations of the illusion are shown with one vanishing point, as well as from an inverted perspective where the scrolls appear to originate in the distance. The demos highlight the conflict between the physical lines in the picture plane and perspective interpretation: With two perspective points, the scrolling texts are parallel to each other in the picture plane but not in perspective interpretation; with one perspective point, the texts are not parallel to each other in the picture plane but are parallel to each other in perspective interpretation. The size of the effect is linearly related to the angle of rotation of the scrolls into the third dimension; the Scroll Illusion is stronger than the Leaning Tower Illusion for rotation angles between 35° and 90°. There is no effect of motion per se on the strength of the illusion.

The 'bookshelf illusion'--a real-world Zöllner-type illusion?

Science.gov (United States)

MacLin, Otto H; Peterson, Dwight J

2010-01-01

We discovered an interesting perceptual distortion in our office where an upright lamp in front of a bookshelf was noticeably curved to form several subtle S-shaped bends. We realized that the books in the bookshelf fell in a particular manner, leaning in alternative directions, which caused the straight lamp to appear bent, creating what may be a real-world example of the Zöllner illusion. Evidence for the production of the illusion diagrammatically and an explanation for the effect are provided.

Strange-face illusions during inter-subjective gazing.

Science.gov (United States)

Caputo, Giovanni B

2013-03-01

In normal observers, gazing at one's own face in the mirror for a few minutes, at a low illumination level, triggers the perception of strange faces, a new visual illusion that has been named 'strange-face in the mirror'. Individuals see huge distortions of their own faces, but they often see monstrous beings, archetypal faces, faces of relatives and deceased, and animals. In the experiment described here, strange-face illusions were perceived when two individuals, in a dimly lit room, gazed at each other in the face. Inter-subjective gazing compared to mirror-gazing produced a higher number of different strange-faces. Inter-subjective strange-face illusions were always dissociative of the subject's self and supported moderate feeling of their reality, indicating a temporary lost of self-agency. Unconscious synchronization of event-related responses to illusions was found between members in some pairs. Synchrony of illusions may indicate that unconscious response-coordination is caused by the illusion-conjunction of crossed dissociative strange-faces, which are perceived as projections into each other's visual face of reciprocal embodied representations within the pair. Inter-subjective strange-face illusions may be explained by the subject's embodied representations (somaesthetic, kinaesthetic and motor facial pattern) and the other's visual face binding. Unconscious facial mimicry may promote inter-subjective illusion-conjunction, then unconscious joint-action and response-coordination. Copyright © 2012 Elsevier Inc. All rights reserved.

Laterality in the rubber hand illusion.

Science.gov (United States)

Ocklenburg, Sebastian; Rüther, Naima; Peterburs, Jutta; Pinnow, Marlies; Güntürkün, Onur

2011-03-01

In patient studies, impairments of sense of body ownership have repeatedly been linked to right-hemispheric brain damage. To test whether a right-hemispheric dominance for sense of body ownership could also be observed in healthy adults, the rubber hand illusion was elicited on both hands of 21 left-handers and 22 right-handers. In this illusion, a participant's real hand is stroked while hidden from view behind an occluder, and a nearby visible hand prosthesis is repeatedly stroked in synchrony. Most participants experience the illusionary perception of touch sensations arising from the prosthesis. The vividness of the illusion was measured by subjective self-reports as well as by skin conductance responses to watching the rubber hand being harmed. Handedness did not affect the vividness of the illusion, but a stronger skin conductance response was observed, when the illusion was elicited on the left hand. These findings suggest a right-hemispheric dominance for sense of body ownership in healthy adults.

Taking aim at Müller-Lyer goalkeeper illusion: An illusion bias in action that originates from the target not being optically specified.

NARCIS (Netherlands)

Shim, J.; van der Kamp, J.; Rigby, B.R.; Lutz, R.; Poolton, J.M.; Masters, R.S.W.

2014-01-01

Van der Kamp and Masters (2008) reported that goalkeeper postures that mimic the Müller-Lyer (1889) illusion affect the location of handball penalty throws. In four experiments, we aimed to verify that the effects on throwing are consistent with an illusorybias(Experiments 1 and 2), and to examine

The Effects of Optical Illusions in Perception and Action in Peripersonal and Extrapersonal Space.

Science.gov (United States)

Shim, Jaeho; van der Kamp, John

2017-09-01

While the two visual system hypothesis tells a fairly compelling story about perception and action in peripersonal space (i.e., within arm's reach), its validity for extrapersonal space is very limited and highly controversial. Hence, the present purpose was to assess whether perception and action differences in peripersonal space hold in extrapersonal space and are modulated by the same factors. To this end, the effects of an optic illusion in perception and action in both peripersonal and extrapersonal space were compared in three groups that threw balls toward a target at a distance under different target eccentricity (i.e., with the target fixated and in peripheral field), viewing (i.e., binocular and monocular viewing), and delay conditions (i.e., immediate and delayed action). The illusory bias was smaller in action than in perception in peripersonal space, but this difference was significantly reduced in extrapersonal space, primarily because of a weakening bias in perception. No systematic modulation of target eccentricity, viewing, and delay arose. The findings suggest that the two visual system hypothesis is also valid for extra personal space.

OPTICAL ILLUSION DESIGN BASED ON FOUR CONVEX LENSES SYSTEM AND CLOAKING AREA CHARACTERIZATION

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I. T. Sugiarto

2018-01-01

Full Text Available A set up of optical illusion based on 4f system and characterization of cloaking area have been carried out. The cloaking area is an area where the object is placed on the area as if it disappears from view; the set-up of cloaking area is located at the top of the third lens. The distance between the lens and the cloaking, which is generated from 4f system, depends on the size of the focal point and the size of the lens used. The larger the focal point of the lens used the wider the distance between the lenses and the larger the size of the diameter of the lens, the cloaking range will be increasingly wide, and vice versa. From the experimental results that we obtained that the cloaking area for set up using FL (focusing lens 100, 50, 50 and 100 mm with a diameter of 3.6 cm lens is ± 2 cm, whereas for the set up using lens FL 150, 100, 100 and 150 mm with lens diameter 2.54 cm is ± 1 cm.

The Café Wall Illusion: Local and Global Perception from Multiple Scales to Multiscale

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Nasim Nematzadeh

2017-01-01

Full Text Available Geometrical illusions are a subclass of optical illusions in which the geometrical characteristics of patterns in particular orientations and angles are distorted and misperceived as a result of low-to-high-level retinal/cortical processing. Modelling the detection of tilt in these illusions, and its strength, is a challenging task and leads to the development of techniques that explain important features of human perception. We present here a predictive and quantitative approach for modelling foveal and peripheral vision for the induced tilt in the Café Wall illusion, in which parallel mortar lines between shifted rows of black and white tiles appear to converge and diverge. Difference of Gaussians is used to define a bioderived filtering model for the responses of retinal simple cells to the stimulus, while an analytical processing pipeline is developed to quantify the angle of tilt in the model and develop confidence intervals around them. Several sampling sizes and aspect ratios are explored to model variant foveal views, and a variety of pattern configurations are tested to model variant Gestalt views. The analysis of our model across this range of test configurations presents a precisely quantified comparison contrasting local tilt detection in the foveal sample sets with pattern-wide Gestalt tilt.

[Neuromolecular mechanism of the superiority illusion].

Science.gov (United States)

Yamada, Makiko

2014-01-01

The majority of individuals evaluate themselves as above average. This is a cognitive bias called "the superiority illusion". This illusory self-evaluation helps us to have hopes for the future, and has been central to the process of human evolution. Possessing this illusion is also important for mental health, as depressed people appear to have a more realistic perception of themselves, dubbed "depressive realism". Our recent study revealed the spontaneous brain activity and central dopaminergic neurotransmission that generate this illusion, using resting-state fMRI and PET. A functional connectivity between the frontal cortex and striatum, regulated by inhibitory dopaminergic neurotransmission, determines individual levels of the superiority illusion. We further revealed that blocking the dopamine transporter, which enhanced the level of dopamine, increased the degree of the superiority illusion. These findings suggest that dopamine acts on striatal dopamine receptors to suppress fronto-striatal functional connectivity, leading to disinhibited, heuristic, approaches to positive self-evaluation. These findings help us to understand how this key aspect of the human mind is biologically determined, and will suggest treatments for depressive symptoms by targeting specific molecules and neural circuits.

The costs and benefits of positive illusions.

Science.gov (United States)

Makridakis, Spyros; Moleskis, Andreas

2015-01-01

Positive illusions are associated with unrealistic optimism about the future and an inflated assessment of one's abilities. They are prevalent in normal life and are considered essential for maintaining a healthy mental state, although, there are disagreements to the extent to which people demonstrate these positive illusions and whether they are beneficial or not. But whatever the situation, it is hard to dismiss their existence and their positive and/or negative influence on human behavior and decision making in general. Prominent among illusions is that of control, that is "the tendency for people to overestimate their ability to control events." This paper describes positive illusions, their potential benefits but also quantifies their costs in five specific fields (gambling, stock and other markets, new firms and startups, preventive medicine and wars). It is organized into three parts. First the psychological reasons giving rise to positive illusions are described and their likely harm and benefits stated. Second, their negative consequences are presented and their costs are quantified in five areas seriously affected with emphasis to those related to the illusion of control that seems to dominate those of unrealistic optimism. The costs involved are huge and serious efforts must be undertaken to understand their enormity and steps taken to avoid them in the future. Finally, there is a concluding section where the challenges related to positive illusions are noted and directions for future research are presented.

Virtual hand illusion induced by visuomotor correlations.

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Maria V Sanchez-Vives

Full Text Available BACKGROUND: Our body schema gives the subjective impression of being highly stable. However, a number of easily-evoked illusions illustrate its remarkable malleability. In the rubber-hand illusion, illusory ownership of a rubber-hand is evoked by synchronous visual and tactile stimulation on a visible rubber arm and on the hidden real arm. Ownership is concurrent with a proprioceptive illusion of displacement of the arm position towards the fake arm. We have previously shown that this illusion of ownership plus the proprioceptive displacement also occurs towards a virtual 3D projection of an arm when the appropriate synchronous visuotactile stimulation is provided. Our objective here was to explore whether these illusions (ownership and proprioceptive displacement can be induced by only synchronous visuomotor stimulation, in the absence of tactile stimulation. METHODOLOGY/PRINCIPAL FINDINGS: To achieve this we used a data-glove that uses sensors transmitting the positions of fingers to a virtually projected hand in the synchronous but not in the asynchronous condition. The illusion of ownership was measured by means of questionnaires. Questions related to ownership gave significantly larger values for the synchronous than for the asynchronous condition. Proprioceptive displacement provided an objective measure of the illusion and had a median value of 3.5 cm difference between the synchronous and asynchronous conditions. In addition, the correlation between the feeling of ownership of the virtual arm and the size of the drift was significant. CONCLUSIONS/SIGNIFICANCE: We conclude that synchrony between visual and proprioceptive information along with motor activity is able to induce an illusion of ownership over a virtual arm. This has implications regarding the brain mechanisms underlying body ownership as well as the use of virtual bodies in therapies and rehabilitation.

No pain relief with the rubber hand illusion.

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Rahul Mohan

Full Text Available The sense of body ownership can be easily disrupted during illusions and the most common illusion is the rubber hand illusion. An idea that is rapidly gaining popularity in clinical pain medicine is that body ownership illusions can be used to modify pathological pain sensations and induce analgesia. However, this idea has not been empirically evaluated. Two separate research laboratories undertook independent randomized repeated measures experiments, both designed to detect an effect of the rubber hand illusion on experimentally induced hand pain. In Experiment 1, 16 healthy volunteers rated the pain evoked by noxious heat stimuli (5 s duration; interstimulus interval 25 s of set temperatures (47°, 48° and 49°C during the rubber hand illusion or during a control condition. There was a main effect of stimulus temperature on pain ratings, but no main effect of condition (p = 0.32, nor a condition x temperature interaction (p = 0.31. In Experiment 2, 20 healthy volunteers underwent quantitative sensory testing to determine heat and cold pain thresholds during the rubber hand illusion or during a control condition. Secondary analyses involved heat and cold detection thresholds and paradoxical heat sensations. Again, there was no main effect of condition on heat pain threshold (p = 0.17, nor on cold pain threshold (p = 0.65, nor on any of the secondary measures (p<0.56 for all. We conclude that the rubber hand illusion does not induce analgesia.

Fun with maths and physics: brain teasers tricks illusions

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Perelman, Yakov

2013-01-01

Fun with Maths and Physics details a large number of intriguing physics experiments, entertaining mathematics problems, and amazing optical illusions.The book’s main objective is to arouse the reader’s scientific imagination, teach him to think in a scientific manner, and create in his mind a variety of associations between physical knowledge and a large number of real daily life observations.Immensely instructive and entertaining, it has been one of the best sellers in Russia during the first part of last century.

Review of Studies on Visual Perception in Grey Parrots (Psittacus erithacus: The Muller-Lyer Illusion, Amodal and Modal Completion

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Irene M. Pepperberg

2017-08-01

Full Text Available Few avian studies on optical illusions are directly comparable to those with humans. Grey parrots that have some referential use of English speech, however, allow for such comparative studies, as these birds can be tested just as are humans, by asking them to describe exactly what they have seen. Here I review two studies, one on the Müller-Lyer illusion (Pepperberg, Vicinay, & Cavanagh, 2008, one on amodal and modal perception (Pepperberg & Nakayama, 2016, that demonstrate similarities between human and Grey parrot perceptual abilities.

Geometrical illusions are not always where you think they are

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Jacques eNinio

2014-10-01

Full Text Available Geometrical illusions are known through a small core of classical illusions that were discovered in the second half of the 19th century. Most experimental studies and most theoretical discussions revolve around this core of illusions, as though all other illusions were obvious variants of these. Yet, many illusions, mostly described by German authors at the same time or at the beginning of the 20th century have been forgotten and are awaiting their rehabilitation. Recently, several new illusions were discovered, mainly by Italian authors, and they do not seem to take place into any current classification. Among the principles that are invoked to explain the illusions, there are principles relating to the metric aspects (contrast, assimilation, shrinkage, expansion, attraction of parallels principles relating to orientations (regression to right angles, orthogonal expansion or, more recently, to gestalt effects. It is possible to oppose, to many a classical stimulus, an illusion that apparently contradicts the lesson derived from this stimulus. Furthermore, some well-known illusory patterns may not be illusions at all, they capture legitimate paradoxes of shape perception.Here, metric effects are discussed within a measurement framework, in which the geometric illusions are the outcome of a measurement process. There would be a main convexity bias in the measures: the measured value m(x of an extant x would grow more than proportionally with x. This convexity principle, completed by a principle of compromise for conflicting measures can replace, for a large number of patterns, both the assimilation and the contrast effects. We know from evolutionary theory that the most pertinent classification criteria may not be the most salient ones (e.g., a dolphin is not a mammal. In order to obtain an objective classification of illusions, I initiated with Kevin O’Regan systematic work on orientation profiles (describing how the strength of an illusion

The time constant of the somatogravic illusion.

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Correia Grácio, B J; de Winkel, K N; Groen, E L; Wentink, M; Bos, J E

2013-02-01

Without visual feedback, humans perceive tilt when experiencing a sustained linear acceleration. This tilt illusion is commonly referred to as the somatogravic illusion. Although the physiological basis of the illusion seems to be well understood, the dynamic behavior is still subject to discussion. In this study, the dynamic behavior of the illusion was measured experimentally for three motion profiles with different frequency content. Subjects were exposed to pure centripetal accelerations in the lateral direction and were asked to indicate their tilt percept by means of a joystick. Variable-radius centrifugation during constant angular rotation was used to generate these motion profiles. Two self-motion perception models were fitted to the experimental data and were used to obtain the time constant of the somatogravic illusion. Results showed that the time constant of the somatogravic illusion was on the order of two seconds, in contrast to the higher time constant found in fixed-radius centrifugation studies. Furthermore, the time constant was significantly affected by the frequency content of the motion profiles. Motion profiles with higher frequency content revealed shorter time constants which cannot be explained by self-motion perception models that assume a fixed time constant. Therefore, these models need to be improved with a mechanism that deals with this variable time constant. Apart from the fundamental importance, these results also have practical consequences for the simulation of sustained accelerations in motion simulators.

Illusion optics: Optically transforming the nature and the location of electromagnetic emissions

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Yi, Jianjia; Tichit, Paul-Henri; Burokur, Shah Nawaz; de Lustrac, André

2015-02-01

Complex electromagnetic structures can be designed by using the powerful concept of transformation electromagnetics. In this study, we define a spatial coordinate transformation that shows the possibility of designing a device capable of producing an illusion on an antenna radiation pattern. Indeed, by compressing the space containing a radiating element, we show that it is able to change the radiation pattern and to make the radiation location appear outside the latter space. Both continuous and discretized models with calculated electromagnetic parameter values are presented. A reduction of the electromagnetic material parameters is also proposed for a possible physical fabrication of the device with achievable values of permittivity and permeability that can be obtained from existing well-known metamaterials. Following that, the design of the proposed antenna using a layered metamaterial is presented. Full wave numerical simulations using Finite Element Method are performed to demonstrate the performances of such a device.

Illusion optics: Optically transforming the nature and the location of electromagnetic emissions

International Nuclear Information System (INIS)

Yi, Jianjia; Tichit, Paul-Henri; Burokur, Shah Nawaz; Lustrac, André de

2015-01-01

Complex electromagnetic structures can be designed by using the powerful concept of transformation electromagnetics. In this study, we define a spatial coordinate transformation that shows the possibility of designing a device capable of producing an illusion on an antenna radiation pattern. Indeed, by compressing the space containing a radiating element, we show that it is able to change the radiation pattern and to make the radiation location appear outside the latter space. Both continuous and discretized models with calculated electromagnetic parameter values are presented. A reduction of the electromagnetic material parameters is also proposed for a possible physical fabrication of the device with achievable values of permittivity and permeability that can be obtained from existing well-known metamaterials. Following that, the design of the proposed antenna using a layered metamaterial is presented. Full wave numerical simulations using Finite Element Method are performed to demonstrate the performances of such a device

The Emergence of Figural Effects in the Watercolor Illusion

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Pinna, Baingio; Penna, Maria Pietronilla

The watercolor illusion is characterized by a large-scale assimilative color spreading (coloration effect) emanating from thin colored edges. The watercolor illusion enhances the figural properties of the colored areas and imparts to the surrounding area the perceptual status of background. This work explores interactions between cortical boundary and surface processes by presenting displays and psychophysical experiments that exhibit new properties of the watercolor illusion. The watercolor illusion is investigated as supporting a new principle of figure-ground organization when pitted against principles of surroundedness, relative orientation, and Prägnanz. The work demonstrated that the watercolor illusion probes a unique combination of visual processes that set it apart from earlier Gestalt principles, and can compete successfully against them. This illusion exemplifies how long-range perceptual effects may be triggered by spatially sparse information. All the main effects are explained by the FACADE model of biological vision, which clarifies how local properties control depthful filling-in of surface lightness and color.

Self-Enhancing Illusions among Chinese Schoolchildren.

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Falbo, Toni; And Others

1997-01-01

Demonstrates that East Asian children (EAC) do engage in some forms of self-enhancing illusions. Responses from 4,000 elementary school students reveal EACs see themselves as possessing more positive attributes than others. Variations in self-enhancing illusions were found for age, gender, and region of residence. Results are discussed in terms of…

Fiber Optics: No Illusion.

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American School and University, 1983

1983-01-01

A campus computer center at Hofstra University (New York) that holds 70 terminals for student use was first a gymnasium, then a language laboratory. Strands of fiber optics are used for the necessary wiring. (MLF)

No Pain Relief with the Rubber Hand Illusion

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Petkova, Valeria I.; Dey, Abishikta; Barnsley, Nadia; Ingvar, Martin; McAuley, James H.; Moseley, G. Lorimer; Ehrsson, Henrik H.

2012-01-01

The sense of body ownership can be easily disrupted during illusions and the most common illusion is the rubber hand illusion. An idea that is rapidly gaining popularity in clinical pain medicine is that body ownership illusions can be used to modify pathological pain sensations and induce analgesia. However, this idea has not been empirically evaluated. Two separate research laboratories undertook independent randomized repeated measures experiments, both designed to detect an effect of the rubber hand illusion on experimentally induced hand pain. In Experiment 1, 16 healthy volunteers rated the pain evoked by noxious heat stimuli (5 s duration; interstimulus interval 25 s) of set temperatures (47°, 48° and 49°C) during the rubber hand illusion or during a control condition. There was a main effect of stimulus temperature on pain ratings, but no main effect of condition (p = 0.32), nor a condition x temperature interaction (p = 0.31). In Experiment 2, 20 healthy volunteers underwent quantitative sensory testing to determine heat and cold pain thresholds during the rubber hand illusion or during a control condition. Secondary analyses involved heat and cold detection thresholds and paradoxical heat sensations. Again, there was no main effect of condition on heat pain threshold (p = 0.17), nor on cold pain threshold (p = 0.65), nor on any of the secondary measures (pillusion does not induce analgesia. PMID:23285026

The sound-induced phosphene illusion.

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Bolognini, Nadia; Convento, Silvia; Fusaro, Martina; Vallar, Giuseppe

2013-12-01

Crossmodal illusions clearly show how perception, rather than being a modular and self-contained function, can be dramatically altered by interactions between senses. Here, we provide evidence for a novel crossmodal "physiological" illusion, showing that sounds can boost visual cortical responses in such a way to give rise to a striking illusory visual percept. In healthy participants, a single-pulse transcranial magnetic stimulation (sTMS) delivered to the occipital cortex evoked a visual percept, i.e., a phosphene. When sTMS is accompanied by two auditory beeps, the second beep induces in neurologically unimpaired participants the perception of an illusory second phosphene, namely the sound-induced phosphene illusion. This perceptual "fission" of a single phosphene, due to multiple beeps, is not matched by a "fusion" of double phosphenes due to a single beep, and it is characterized by an early auditory modulation of the TMS-induced visual responses (~80 ms). Multiple beeps also induce an illusory feeling of multiple TMS pulses on the participants' scalp, consistent with an audio-tactile fission illusion. In conclusion, an auditory stimulation may bring about a phenomenological change in the conscious visual experience produced by the transcranial stimulation of the occipital cortex, which reveals crossmodal binding mechanisms within early stages of visual processing.

Neural correlates of auditory scale illusion.

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Kuriki, Shinya; Numao, Ryousuke; Nemoto, Iku

2016-09-01

The auditory illusory perception "scale illusion" occurs when ascending and descending musical scale tones are delivered in a dichotic manner, such that the higher or lower tone at each instant is presented alternately to the right and left ears. Resulting tone sequences have a zigzag pitch in one ear and the reversed (zagzig) pitch in the other ear. Most listeners hear illusory smooth pitch sequences of up-down and down-up streams in the two ears separated in higher and lower halves of the scale. Although many behavioral studies have been conducted, how and where in the brain the illusory percept is formed have not been elucidated. In this study, we conducted functional magnetic resonance imaging using sequential tones that induced scale illusion (ILL) and those that mimicked the percept of scale illusion (PCP), and we compared the activation responses evoked by those stimuli by region-of-interest analysis. We examined the effects of adaptation, i.e., the attenuation of response that occurs when close-frequency sounds are repeated, which might interfere with the changes in activation by the illusion process. Results of the activation difference of the two stimuli, measured at varied tempi of tone presentation, in the superior temporal auditory cortex were not explained by adaptation. Instead, excess activation of the ILL stimulus from the PCP stimulus at moderate tempi (83 and 126 bpm) was significant in the posterior auditory cortex with rightward superiority, while significant prefrontal activation was dominant at the highest tempo (245 bpm). We suggest that the area of the planum temporale posterior to the primary auditory cortex is mainly involved in the illusion formation, and that the illusion-related process is strongly dependent on the rate of tone presentation. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of Background Patterns in the Reverse Perspective Illusion

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Takefumi Hayashi

2011-05-01

Full Text Available The reverse perspective (RP illusion is classified as a motion illusion due to inverted depth perception, similar to the Mach book and hollow mask illusions. Distortional motion of a rigid object surface is observed when an observer moves in front of the object which has a texture pattern giving inverted perspective cues (RP object. In this research, we studied the influence of the background pattern of the RP objects on the strength of the illusion. To perform quantitative evaluation, a stereo computer-graphics technique was used. Computer generated right- and left-eye images of an RP object were shown separately to the subjects' eyes through a haploscope. Using a computer key board, they adjusted the binocular disparity of the stereo images so that depth inversion due to the surface texture occurs. We evaluated the strength of the illusion by the critical value of the disparity and found that the background texture is an important factor determining the strength of the RP illusion. Especially, the texture in the horizontal direction creates stronger depth inversion effect compared to the vertical pattern. Using our experimental system, the influences of various pictorial cues on the RP illusion can be studied quantitatively.

The Marble-Hand Illusion.

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Senna, Irene; Maravita, Angelo; Bolognini, Nadia; Parise, Cesare V

2014-01-01

Our body is made of flesh and bones. We know it, and in our daily lives all the senses constantly provide converging information about this simple, factual truth. But is this always the case? Here we report a surprising bodily illusion demonstrating that humans rapidly update their assumptions about the material qualities of their body, based on their recent multisensory perceptual experience. To induce a misperception of the material properties of the hand, we repeatedly gently hit participants' hand with a small hammer, while progressively replacing the natural sound of the hammer against the skin with the sound of a hammer hitting a piece of marble. After five minutes, the hand started feeling stiffer, heavier, harder, less sensitive, unnatural, and showed enhanced Galvanic skin response (GSR) to threatening stimuli. Notably, such a change in skin conductivity positively correlated with changes in perceived hand stiffness. Conversely, when hammer hits and impact sounds were temporally uncorrelated, participants did not spontaneously report any changes in the perceived properties of the hand, nor did they show any modulation in GSR. In two further experiments, we ruled out that mere audio-tactile synchrony is the causal factor triggering the illusion, further demonstrating the key role of material information conveyed by impact sounds in modulating the perceived material properties of the hand. This novel bodily illusion, the 'Marble-Hand Illusion', demonstrates that the perceived material of our body, surely the most stable attribute of our bodily self, can be quickly updated through multisensory integration.

Information processing correlates of a size-contrast illusion

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Jason M Gold

2014-02-01

Full Text Available Perception is often influenced by context. A well-known class of perceptual context effects is perceptual contrast illusions, in which proximate stimulus regions interact to alter the perception of various stimulus attributes, such as perceived brightness, color and size. Although the phenomenal reality of contrast effects is well documented, in many cases the connection between these illusions and how information is processed by perceptual systems is not well understood. Here, we use noise as a tool to explore the information processing correlates of one such contrast effect: the Ebbinghaus-Titchener size-contrast illusion. In this illusion, the perceived size of a central dot is significantly altered by the sizes of a set of surrounding dots, such that the presence of larger surrounding dots tends to reduce the perceived size of the central dot (and vise-versa. In our experiments, we first replicated previous results that have demonstrated the subjective reality of the Ebbinghaus-Titchener illusion. We then used visual noise in a detection task to probe the manner in which observers processed information when experiencing the illusion. By correlating the noise with observers’ classification decisions, we found that the sizes of the surrounding contextual elements had a direct influence on the relative weight observers assigned to regions within and surrounding the central element. Specifically, observers assigned relatively more weight to the surrounding region and less weight to the central region in the presence of smaller surrounding contextual elements. These results offer new insights into the connection between the subjective experience of size-contrast illusions and their associated information processing correlates.

Quantifying the Ebbinghaus figure effect: Target size, context size, and target-context distance determine the presence and direction of the illusion.

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Hester eKnol

2015-11-01

Full Text Available Over the last 20 years, visual illusions, like the Ebbinghaus figure, have become widespread to investigate functional segregation of the visual system. This segregation reveals itself, so it is claimed, in the insensitivity of movement to optical illusions. This claim, however, faces contradictory results (and interpretations in the literature. These contradictions may be due to methodological weaknesses in, and differences across studies, some of which may hide a lack of perceptual illusion effects. Indeed, despite the long history of research with the Ebbinghaus figure, standardized configurations to predict the illusion effect are missing. Here, we present a complete geometrical description of the Ebbinghaus figure with three target sizes compatible with Fitts’ task. Each trial consisted of a stimulus and an isolated probe. The probe was controlled by the participant’s response through a staircase procedure. The participant was asked whether the probe or target appeared bigger. The factors target size, context size, target-context distance, and a control condition resulted in a 3×3×3+3 factorial design. The results indicate that the illusion magnitude, the perceptual distinctiveness, and the response time depend on the context size, distance, and especially, target size. In 33% of the factor combinations there was no illusion effect. The illusion magnitude ranged from zero to (exceptionally ten percent of the target size. The small (or absent illusion effects on perception and its possible influence on motor tasks might have been overlooked or misinterpreted in previous studies. Our results provide a basis for the application of the Ebbinghaus figure in psychophysical and motor control studies.

Homo Novus - A Human Without Illusions

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Frey, Ulrich J; Willführ, Kai P

2010-01-01

Converging evidence from disciplines including sociobiology, evolutionary psychology and human biology forces us to adopt a new idea of what it means to be a human. As cherished concepts such as free will, naïve realism, humans as creation's crowning glory fall and our moral roots in ape group dynamics become clearer, we have to take leave of many concepts that have been central to defining our humanness. What emerges is a new human, the homo novus, a human being without illusions. Leading authors from many different fields explore these issues by addressing these illusions and providing evidence for the need to switch to this new idea of man, in spite of understandable reluctance to let go of our most beloved illusions.

The nonvisual illusion of self-touch: Misaligned hands and anatomical implausibility.

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White, Rebekah C; Weinberg, Jennifer L; Aimola Davies, Anne M

2015-01-01

The self-touch illusion is elicited when the participant (with eyes closed) administers brushstrokes to a prosthetic hand while the examiner administers synchronous brushstrokes to the participant's other (receptive) hand. In three experiments we investigated the effects of misalignment on the self-touch illusion. In experiment 1 we manipulated alignment (0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees) of the prosthetic hand relative to the participant's receptive hand. The illusion was equally strong at 0 degrees and 45 degrees: the two conditions in which the prosthetic hand was in an anatomically plausible orientation. To investigate whether the illusion was diminished at 90 degrees (and beyond) by anatomical implausibility rather than by misalignment, in experiment 2 hand positioning was changed. The illusion was equally strong at 0 degrees, 45 degrees, and 90 degrees, but diminished at 135 degrees despite the prosthetic hand now being in an anatomically plausible orientation. Thus the illusion is diminished with misalignment of 135 degrees, irrespective of anatomical plausibility. Having demonstrated that the illusion was equally strong with the hands aligned (0 degrees) or misaligned by 45 degrees, in experiment 3 we demonstrated that participants did not detect a 45 degrees misalignment. Large degrees of misalignment prevent a compelling experience of the self-touch illusion, and the self-touch illusion prevents detection of small degrees of misalignment.

Looking at Op Art: Gaze stability and motion illusions.

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Hermens, Frouke; Zanker, Johannes

2012-01-01

Various Op artists have used simple geometrical patterns to create the illusion of motion in their artwork. One explanation for the observed illusion involves retinal shifts caused by small involuntary eye movements that observers make while they try to maintain fixation. Earlier studies have suggested a prominent role of the most conspicuous of these eye movements, small rapid position shifts called microsaccades. Here, we present data that could expand this view with a different interpretation. In three experiments, we recorded participants' eye movements while they tried to maintain visual fixation when being presented with variants of Bridget Riley's Fall, which were manipulated such as to vary the strength of induced motion. In the first two experiments, we investigated the properties of microsaccades for a set of stimuli with known motion strengths. In agreement with earlier observations, microsaccade rates were unaffected by the stimulus pattern and, consequently, the strength of induced motion illusion. In the third experiment, we varied the stimulus pattern across a larger range of parameters and asked participants to rate the perceived motion illusion. The results revealed that motion illusions in patterns resembling Riley's Fall are perceived even in the absence of microsaccades, and that the reported strength of the illusion decreased with the number of microsaccades in the trial. Together, the three experiments suggest that other sources of retinal image instability than microsaccades, such as slow oculomotor drift, should be considered as possible factors contributing to the illusion.

Relative contribution of lateral inhibition to the Delboeuf and Wundt-Hering illusions.

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Coren, S

1999-06-01

It has been suggested that lateral neural interactions contribute to some illusions with intersecting or converging line elements but cannot be present in figures that lack these components. Most attempts to ascertain the contribution of neural interactions in visual illusions have involved changes in the actual pattern of illusion. It has now been demonstrated that certain forms of intermittent light stimulation can enhance lateral inhibitory activity. The Wundt-Hering and the Delboeuf illusions were tested under continuous illumination and "shaped" intermittent illumination which augments lateral inhibition. As expected, the Delboeuf illusion was unchanged with increased lateral inhibition while the magnitude of the Wundt-Hering illusion increased.

The building blocks of the full body ownership illusion

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Antonella eMaselli

2013-03-01

Full Text Available Previous work has reported that it is not difficult to give people the illusion of ownership over an artificial body, providing a powerful tool for the investigation of the neural and cognitive mechanisms underlying body perception and self consciousness. We present an experimental study that uses immersive virtual reality focused on identifying the perceptual building blocks of this illusion. We systematically manipulated visuotactile and visual sensorimotor contingencies, visual perspective, and the appearance of the virtual body in order to assess their relative role and mutual interaction. Consistent results from subjective reports and physiological measures showed that a first person perspective over a fake humanoid body is essential for eliciting a body ownership illusion. We found that the level of realism of the virtual body, in particular the realism of skin tone, plays a critical role: when high enough, the illusion can be triggered by the sole effect of the spatial overlap between the real and virtual bodies, providing congruent visuoproprioceptive information, with no need for the additional contribution of congruent visuotactile and/or visual sensorimotor cues. Additionally, we found that the processing of incongruent perceptual cues can be modulated by the level of the illusion: when the illusion is strong, incongruent cues are not experienced as incorrect. Participants exposed to asynchronous visuotactile stimulation can experience the ownership illusion and perceive touch as originating from an object seen to contact the virtual body. Analogously, when the level of realism of the virtual body and/or the spatial overlap of the two bodies is not high enough, the contribution of congruent multisensory and/or sensorimotor cues is required for evoking the illusion. On the basis of these results and inspired by findings from neurophysiological recordings in the monkey, we propose a model that accounts for many of the results reported

The building blocks of the full body ownership illusion

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Maselli, Antonella; Slater, Mel

2013-01-01

Previous work has reported that it is not difficult to give people the illusion of ownership over an artificial body, providing a powerful tool for the investigation of the neural and cognitive mechanisms underlying body perception and self consciousness. We present an experimental study that uses immersive virtual reality (IVR) focused on identifying the perceptual building blocks of this illusion. We systematically manipulated visuotactile and visual sensorimotor contingencies, visual perspective, and the appearance of the virtual body in order to assess their relative role and mutual interaction. Consistent results from subjective reports and physiological measures showed that a first person perspective over a fake humanoid body is essential for eliciting a body ownership illusion. We found that the illusion of ownership can be generated when the virtual body has a realistic skin tone and spatially substitutes the real body seen from a first person perspective. In this case there is no need for an additional contribution of congruent visuotactile or sensorimotor cues. Additionally, we found that the processing of incongruent perceptual cues can be modulated by the level of the illusion: when the illusion is strong, incongruent cues are not experienced as incorrect. Participants exposed to asynchronous visuotactile stimulation can experience the ownership illusion and perceive touch as originating from an object seen to contact the virtual body. Analogously, when the level of realism of the virtual body is not high enough and/or when there is no spatial overlap between the two bodies, then the contribution of congruent multisensory and/or sensorimotor cues is required for evoking the illusion. On the basis of these results and inspired by findings from neurophysiological recordings in the monkey, we propose a model that accounts for many of the results reported in the literature. PMID:23519597

The Müller-Lyer illusion in ant foraging.

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Tomoko Sakiyama

Full Text Available The Müller-Lyer illusion is a classical geometric illusion in which the apparent (perceived length of a line depends on whether the line terminates in an arrow tail or arrowhead. This effect may be caused by economic compensation for the gap between the physical stimulus and visual fields. Here, we show that the Müller-Lyer illusion can also be produced by the foraging patterns of garden ants (Lasius niger and that the pattern obtained can be explained by a simple, asynchronously updated foraging ant model. Our results suggest that the geometric illusion may be a byproduct of the foraging process, in which local interactions underlying efficient exploitation can also give rise to global exploration, and that visual information processing in human could implement similar modulation between local efficient processing and widespread computation.

Cortical processes of speech illusions in the general population.

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Schepers, E; Bodar, L; van Os, J; Lousberg, R

2016-10-18

There is evidence that experimentally elicited auditory illusions in the general population index risk for psychotic symptoms. As little is known about underlying cortical mechanisms of auditory illusions, an experiment was conducted to analyze processing of auditory illusions in a general population sample. In a follow-up design with two measurement moments (baseline and 6 months), participants (n = 83) underwent the White Noise task under simultaneous recording with a 14-lead EEG. An auditory illusion was defined as hearing any speech in a sound fragment containing white noise. A total number of 256 speech illusions (SI) were observed over the two measurements, with a high degree of stability of SI over time. There were 7 main effects of speech illusion on the EEG alpha band-the most significant indicating a decrease in activity at T3 (t = -4.05). Other EEG frequency bands (slow beta, fast beta, gamma, delta, theta) showed no significant associations with SI. SIs are characterized by reduced alpha activity in non-clinical populations. Given the association of SIs with psychosis, follow-up research is required to examine the possibility of reduced alpha activity mediating SIs in high risk and symptomatic populations.

Illusion and Illusoriness of Color and Coloration

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Baingio Pinna

2018-01-01

Full Text Available In this work, through a phenomenological analysis, we studied the perception of the chromatic illusion and illusoriness. The necessary condition for an illusion to occur is the discovery of a mismatch/disagreement between the geometrical/physical domain and the phenomenal one. The illusoriness is instead a phenomenal attribute related to a sense of strangeness, deception, singularity, mendacity, and oddity. The main purpose of this work is to study the phenomenology of chromatic illusion vs. illusoriness, which is useful for shedding new light on the no-man’s land between “sensory” and “cognitive” processes that have not been fully explored. Some basic psychological and biological implications for living organisms are deduced.

The Illusion of Argument Justification

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Fisher, Matthew; Keil, Frank

2013-01-01

Argumentation is an important way to reach new understanding. Strongly caring about an issue, which is often evident when dealing with controversial issues, has been shown to lead to biases in argumentation. We suggest that people are not well calibrated in assessing their ability to justify a position through argumentation, an effect we call the illusion of argument justification. Furthermore we find that caring about the issue further clouds this introspection. We first show this illusion by measuring the difference between ratings before and after producing an argument for one’s own position. The strength of the illusion is predicted by the strength of care for a given issue (Study 1). The tacit influences of framing and priming do not override the effects of emotional investment in a topic (Study 2). However, explicitly considering counterarguments removes the effect of care when initially assessing the ability to justify a position (Study 3). Finally, we consider our findings in light of other recent research and discuss the potential benefits of group reasoning. PMID:23506085

Do domestic dogs (Canis lupus familiaris) perceive the Delboeuf illusion?

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Miletto Petrazzini, Maria Elena; Bisazza, Angelo; Agrillo, Christian

2017-05-01

In the last decade, visual illusions have been repeatedly used as a tool to compare visual perception among species. Several studies have investigated whether non-human primates perceive visual illusions in a human-like fashion, but little attention has been paid to other mammals, and sensitivity to visual illusions has been never investigated in the dog. Here, we studied whether domestic dogs perceive the Delboeuf illusion. In human and non-human primates, this illusion creates a misperception of item size as a function of its surrounding context. To examine this effect in dogs, we adapted the spontaneous preference paradigm recently used with chimpanzees. Subjects were presented with two plates containing food. In control trials, two different amounts of food were presented in two identical plates. In this circumstance, dogs were expected to select the larger amount. In test trials, equal food portion sizes were presented in two plates differing in size: if dogs perceived the illusion as primates do, they were expected to select the amount of food presented in the smaller plate. Dogs significantly discriminated the two alternatives in control trials, whereas their performance did not differ from chance in test trials with the illusory pattern. The fact that dogs do not seem to be susceptible to the Delboeuf illusion suggests a potential discontinuity in the perceptual biases affecting size judgments between primates and dogs.

Object representations in visual memory: evidence from visual illusions.

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Ben-Shalom, Asaf; Ganel, Tzvi

2012-07-26

Human visual memory is considered to contain different levels of object representations. Representations in visual working memory (VWM) are thought to contain relatively elaborated information about object structure. Conversely, representations in iconic memory are thought to be more perceptual in nature. In four experiments, we tested the effects of two different categories of visual illusions on representations in VWM and in iconic memory. Unlike VWM that was affected by both types of illusions, iconic memory was immune to the effects of within-object contextual illusions and was affected only by illusions driven by between-objects contextual properties. These results show that iconic and visual working memory contain dissociable representations of object shape. These findings suggest that the global properties of the visual scene are processed prior to the processing of specific elements.

What visual illusions teach us about schizophrenia

Directory of Open Access Journals (Sweden)

Charles-Edouard eNotredame

2014-08-01

Full Text Available Illusion, namely a mismatch between the objective and perceived properties of an object present in the environment, is a common feature of visual perception, both in normal and pathological conditions. This makes illusion a valuable tool with which to explore normal perception and its impairments. Although still debated, the hypothesis of a modified, and typically diminished, susceptibility to illusions in schizophrenia patients is supported by a growing number of studies. The current paper aimed to review how illusions have been used to explore and reveal the core features of visual perception in schizophrenia from a psychophysical, neurophysiological and functional point of view. We propose an integration of these findings into a common hierarchical Bayesian inference framework. The Bayesian formalism considers perception as the optimal combination between sensory evidence and prior knowledge, thereby highlighting the interweaving of perceptions and beliefs. Notably, it offers a holistic and convincing explanation for the perceptual changes observed in schizophrenia that might be ideally tested using illusory paradigms, as well as potential paths to explore neural mechanisms. Implications for psychopathology (in terms of positive symptoms, subjective experience or behavior disruptions are critically discussed.

Strange-face-in-the-mirror illusion and schizotypy during adolescence.

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Fonseca-Pedrero, Eduardo; Badoud, Deborah; Antico, Lia; Caputo, Giovanni B; Eliez, Stephan; Schwartz, Sophie; Debbané, Martin

2015-03-01

Patients with schizophrenia can sometimes report strange face illusions when staring at themselves in the mirror; such experiences have been conceptualized as anomalous self-experiences that can be experienced with a varying degree of depersonalization. During adolescence, anomalous self-experiences can also be indicative of increased risk to develop schizophrenia-spectrum disorders. To date however, the Mirror-Gazing test (MGT), an experimentally validated experiment to evaluate the propensity of strange face illusions in nonclinical and clinical adults, has yet to be investigated in an adolescent sample. The first goal of the present study was to examine experimentally induced self-face illusions in a nonclinical sample of adolescents, using the MGT. The second goal was to investigate whether dimensions of adolescent trait schizotypy were differentially related to phenomena arising during the MGT. One hundred and ten community adolescents (59 male) aged from 12 to 19 years (mean age = 16.31, SD age = 1.77) completed the MGT and Schizotypal Personality Questionnaire. The results yielded 4 types of strange face illusions; 2 types of illusions (slight change of light/color [20%] and own face deformation [45.5%]) lacked depersonalization-like phenomena (no identity change), while 2 other types (vision of other identity [27.3%], and vision of non-human identity [7.3%]) contained clear depersonalization-like phenomena. Furthermore, the disorganization dimension of schizotypy associated negatively with time of first illusion (first press), and positively with frequency of illusions during the MGT. Statistically significant differences on positive and disorganized schizotypy were found when comparing groups on the basis of degree of depersonalization-like phenomena (from slight color changes to non-human visions). Similarly to experimentally induced self-face illusions in patients with schizophrenia, such illusions in a group of nonclinical adolescents present

Elevator Illusion and Gaze Direction in Hypergravity

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Cohen, Malcolm M.; Hargens, Alan (Technical Monitor)

1995-01-01

A luminous visual target in a dark hypergravity (Gz greater than 1) environment appears to be elevated above its true physical position. This "elevator illusion" has been attributed to changes in oculomotor control caused by increased stimulation of the otolith organs. Data relating the magnitude of the illusion to the magnitude of the changes in oculomotor control have been lacking. The present study provides such data.

The origins of entasis: illusion, aesthetics or engineering?

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Thompson, Peter; Papadopoulou, Georgia; Vassiliou, Eleni

2007-01-01

A typical characteristic of columns in Doric temples is entasis; a slight convexity in the body of a column. Often, and particularly in guide-books, it is suggested that entasis is intended to compensate for an illusion of concavity in columns with truly straight sides. We have investigated whether any such visual illusion exists, both in parallel sided and in tapering columns in a series of experiments, finding little evidence to support any illusion-compensation theory. Further, we explored the possibility that entasis was employed for purely aesthetic reasons, but the results do not support this conclusion. Finally, evidence supporting an engineering role for entasis is presented.

Functional cortical mapping of scale illusion

International Nuclear Information System (INIS)

Wang, Li-qun; Kuriki, Shinya

2011-01-01

We have studied cortical activation using 1.5 T fMRI during 'Scale Illusion', a kind of auditory illusion, in which subjects perceive smooth melodies while listening to dichotic irregular pitch sequences consisting of scale tones, in repeated phrases composed of eight tones. Four male and four female subjects listened to different stimuli, that including illusion-inducing tone sequence, monaural tone sequence and perceived pitch sequence with a control of white noises delivered to the right and left ears in random order. 32 scans with a repetition time (TR) 3 s Between 3 s interval for each type of the four stimuli were performed. In BOLD signals, activation was observed in the prefrontal and temporal cortices, parietal lobule and occipital areas by first-level group analysis. However, there existed large intersubject variability such that systematic tendency of the activation was not clear. The study will be continued to obtain larger number of subjects for group analysis. (author)

The role of the Gestalt principle of similarity in the watercolor illusion.

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Pinna, Baingio

2005-01-01

The watercolor illusion presents two main effects: a long-range assimilative color spreading (coloration effect), and properties imparting a strong figure status (figural effect) to a region delimited by a dark (e.g. purple) contour flanked by a lighter chromatic contour (e.g. orange). In four experiments, the strength of the watercolor illusion to determine figure-ground organization is directly compared (combined or pitted against) with the Gestalt principle of similarity both of color and line width. The results demonstrated that (i) the watercolor illusion and, particularly, its figural effect won over the classical Gestalt factors of similarity; (ii) the watercolor illusion cannot be due to the coloration effect as suggested by the similarity principle; (iii) coloration and figural effects may be independent in the watercolor illusion, and (iv) the watercolor illusion can be considered as a principle of figure-ground segregation on its own. Two parallel and independent processes as proposed within the FACADE model (Grossberg, 1994, 1997) are suggested to account for the two effects of coloration and figural enhancement in the watercolor illusion.

Paradoxical perception of surfaces in the Shepard tabletop illusion

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Tyler, Christopher W

2011-01-01

The Shepard tabletop illusion, consisting of different perspective embeddings of two identical parallelograms as tabletops, affords a profound difference in their perceived surface shapes. My analysis reveals three further paradoxical aspects of this illusion, in addition to its susceptibility to the ‘inverse perspective illusion’ of the implied orthographic perspective of the table images. These novel aspects of the illusion are: a paradoxical slant of the tabletops, a paradoxical lack of perceived depth, and a paradoxical distortion of the length of the rear legs. The construction of the illusion resembles scenes found in ancient Chinese scroll paintings, and an analysis of the source of the third effect shows that the interpretation in terms of surfaces can account for the difference in treatment of the filled-in versus open forms in the Chinese painting from more than 1000 years ago. PMID:23145230

Can Visual Illusions Be Used to Facilitate Sport Skill Learning?

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Cañal-Bruland, Rouwen; van der Meer, Yor; Moerman, Jelle

2016-01-01

Recently it has been reported that practicing putting with visual illusions that make the hole appear larger than it actually is leads to longer-lasting performance improvements. Interestingly, from a motor control and learning perspective, it may be possible to actually predict the opposite to occur, as facing a smaller appearing target should enforce performers to be more precise. To test this idea the authors invited participants to practice an aiming task (i.e., a marble-shooting task) with either a visual illusion that made the target appear larger or a visual illusion that made the target appear smaller. They applied a pre-post test design, included a control group training without any illusory effects and increased the amount of practice to 450 trials. In contrast to earlier reports, the results revealed that the group that trained with the visual illusion that made the target look smaller improved performance from pre- to posttest, whereas the group practicing with visual illusions that made the target appear larger did not show any improvements. Notably, also the control group improved from pre- to posttest. The authors conclude that more research is needed to improve our understanding of whether and how visual illusions may be useful training tools for sport skill learning.

The Uniformity Illusion

NARCIS (Netherlands)

Otten, Marte; Pinto, Yair; Paffen, C.L.E.; Seth, Anil; Kanai, Ryota

2017-01-01

Vision in the fovea, the center of the visual field, is much more accurate and detailed than vision in the periphery. This is not in line with the rich phenomenology of peripheral vision. Here, we investigated a visual illusion that shows that detailed peripheral visual experience is partially based

Causes of Fiscal Illusion: Lack of Information or Lack of Attention?

DEFF Research Database (Denmark)

Bækgaard, Martin; Serritzlew, Søren; Blom-Hansen, Jens

2016-01-01

the implications of fiscal illusions, whereas the question why fiscal illusions occur at all has received less attention. According to the standard argument, individuals base their opinion of policy proposals on a valuation of benefits and costs. We formalize the standard argument and show that it is a special......According to fiscal illusion theory, voters misperceive fiscal parameters because of incomplete information. The costs of public services are underestimated, implying that if voters had full information, their support for public services would drop. The literature has focused on testing...... case of the attention model of fiscal illusion. In this model, opinion depends on the saliency of attributes of the proposal. We show that the attention model can better explain fiscal illusion by deriving competing hypotheses, which are tested in a survey experiment. We conclude that the mechanism...

Vibration-Induced Kinesthetic Illusions and Corticospinal Excitability Changes.

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Mancheva, Kapka; Rollnik, Jens D; Wolf, Werner; Dengler, Reinhard; Kossev, Andon

2017-01-01

The authors' aim was to investigate the changes of corticospinal excitability during kinesthetic illusions induced by tendon vibration. Motor-evoked potentials in response to transcranial magnetic stimulation were recorded from the vibrated flexor carpi radialis and its antagonist, extensor carpi radialis. The illusions were evoked under vision conditions without feedback for the position of the wrist (open or closed eyes). In these two conditions motor-evoked potential changes during vibration in the antagonist were not identical. This discrepancy may be a result of 2 simultaneously acting, different and opposite influences and the balance between them depends on visual conditions. Thus, the illusion was accompanied by the facilitation of corticospinal excitability in both vibrated muscle and its antagonist.

Creating Virtual-hand and Virtual-face Illusions to Investigate Self-representation.

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Ma, Ke; Lippelt, Dominique P; Hommel, Bernhard

2017-03-01

Studies investigating how people represent themselves and their own body often use variants of "ownership illusions", such as the traditional rubber-hand illusion or the more recently discovered enfacement illusion. However, these examples require rather artificial experimental setups, in which the artificial effector needs to be stroked in synchrony with the participants' real hand or face-a situation in which participants have no control over the stroking or the movements of their real or artificial effector. Here, we describe a technique to establish ownership illusions in a setup that is more realistic, more intuitive, and of presumably higher ecological validity. It allows creating the virtual-hand illusion by having participants control the movements of a virtual hand presented on a screen or in virtual space in front of them. If the virtual hand moves in synchrony with the participants' own real hand, they tend to perceive the virtual hand as part of their own body. The technique also creates the virtual-face illusion by having participants control the movements of a virtual face in front of them, again with the effect that they tend to perceive the face as their own if it moves in synchrony with their real face. Studying the circumstances that illusions of this sort can be created, increased, or reduced provides important information about how people create and maintain representations of themselves.

Conjunction Illusions and Conjunction Fallacies in Episodic Memory

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Brainerd, C. J.; Holliday, Robyn E.; Nakamura, Koyuki; Reyna, Valerie F.

2014-01-01

Recent research on the overdistribution principle implies that episodic memory is infected by conjunction illusions. These are instances in which an item that was presented in a single context (e.g., List 1) is falsely remembered as having been presented in multiple contexts (e.g., List 1 and List 2). Robust conjunction illusions were detected in…

Alexithymia Modulates the Experience of the Rubber Hand Illusion

Directory of Open Access Journals (Sweden)

Delphine eGrynberg

2015-06-01

Full Text Available Alexithymia is associated with lower awareness of emotional and non-emotional internal bodily signals. However, evidence suggesting that alexithymia modulates body awareness at an external level is scarce. This study aimed to investigate whether alexithymia is associated with disrupted multisensory integration by using the rubber hand illusion task.Fifty healthy individuals completed the Toronto Alexithymia Scale and underwent the rubber hand illusion measure. In this measure, one watches a rubber hand being stroked synchronously or asynchronously with one’s own hand, which is hidden from view. Compared to the asynchronous stimulation, the synchronous stimulation results in the illusion that the rubber hand and the participant’s hand are closer together than they really are and that the rubber hand belongs to them. Results revealed that higher levels of alexithymia are associated with a lower ownership illusion. In conclusion, our findings demonstrate that high alexithymia scorers integrate two simultaneous sensory and proprioceptive events into a single experience (lower multisensory integration to a lesser extent than low alexithymia scorers. Higher susceptibility to the illusion in high alexithymia scorers may -indicate that alexithymia is associated with impaired multisensory integration and that this association results from an abnormal focus of one's own body.

A Specific Autistic Trait that Modulates Visuospatial Illusion Susceptibility

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Walter, Elizabeth; Dassonville, Paul; Bochsler, Tiana M.

2009-01-01

Although several accounts of autism have predicted that the disorder should be associated with a decreased susceptibility to visual illusions, previous experimental results have been mixed. This study examined whether a link between autism and illusion susceptibility can be more convincingly demonstrated by assessing the relationships between…

Putting pain out of mind with an 'out of body' illusion.

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Pamment, J; Aspell, J E

2017-02-01

Chronic pain is a growing societal concern that warrants scientific investigation, especially given the ineffectiveness of many treatments. Given evidence that pain experience relies on multisensory integration, there is interest in using body ownership illusions for reducing acute pain. In the present study, we investigate whether patients' experience of chronic pain could be reduced by full body illusions (FBIs) that cause participants to dissociate from their own body. Participants with chronic pain (including sciatica, osteoarthritis, fibromyalgia, muscular pain, IBS and back pain) viewed their own 'virtual' bodies via a video camera and head-mounted display for two minutes. In the 'back-stroking FBI', their backs were stroked with a stick while they viewed synchronous or asynchronous stroking on the virtual body and in the 'front-stroking FBI', they were stroked near their collarbone while viewing the stick approach their field of view in a synchronous or asynchronous fashion. Illusion strength and pain intensity were measured with self-report questionnaires. We found that full body illusions were experienced by patients with chronic pain and further, that pain intensity was reduced by an average of 37% after illusion (synchronous) conditions. These findings add support to theories that high-level multisensory body representations can interact with homeostatic regulation and pain perception. Pain intensity in chronic pain patients was reduced by 37% by 'out of body' illusions. These data demonstrate the potential of such illusions for the management of chronic pain. © 2016 European Pain Federation - EFIC®.

Superiority illusion arises from resting-state brain networks modulated by dopamine.

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Yamada, Makiko; Uddin, Lucina Q; Takahashi, Hidehiko; Kimura, Yasuyuki; Takahata, Keisuke; Kousa, Ririko; Ikoma, Yoko; Eguchi, Yoko; Takano, Harumasa; Ito, Hiroshi; Higuchi, Makoto; Suhara, Tetsuya

2013-03-12

The majority of individuals evaluate themselves as superior to average. This is a cognitive bias known as the "superiority illusion." This illusion helps us to have hope for the future and is deep-rooted in the process of human evolution. In this study, we examined the default states of neural and molecular systems that generate this illusion, using resting-state functional MRI and PET. Resting-state functional connectivity between the frontal cortex and striatum regulated by inhibitory dopaminergic neurotransmission determines individual levels of the superiority illusion. Our findings help elucidate how this key aspect of the human mind is biologically determined, and identify potential molecular and neural targets for treatment for depressive realism.

Illusions of perception of 3-D house models.

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Nielsen, Torsten Ingemann

2008-01-01

In five experiments some edgelines on different polyhedrons (house models in 3-D) were, from a certain vantage point, optically confluent, ie in optical prolongation of each other in 2-D on the retinal image and on photos. Other edgelines on the same polyhedrons were non-confluent, ie optically separate in 2-D. These conditions were found to lead to five different illusory shapes in 3-D. Five spatiofigural illusions were perceived. From these findings an edgeline principle is formulated that: "a straight edgeline in 2-D, whether confluent or separate, is perceived as a unitary and continuously straight edgeline in 3-D". To this is added a supplementary perceptual principle, an amodal completion principle. In the experiments reported here, the illusory perception of shapes in 3-D with confluent edgelines as well as the veridical perception of other shapes in 3-D with only separate or non-confluent edgelines could all be explained by the edgeline principle and the amodal completion principle. By applying the concepts of edgeline confluence and the edgeline principle, a new explanation of the Kopfermann (1930 Psychologische Forschung 13 293- 364) cube phenomena is proposed together with one example of how to test this explanation experimentally.

The moving rubber hand illusion revisited: comparing movements and visuotactile stimulation to induce illusory ownership.

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Kalckert, Andreas; Ehrsson, H Henrik

2014-05-01

The rubber hand illusion is a perceptual illusion in which a model hand is experienced as part of one's own body. In the present study we directly compared the classical illusion, based on visuotactile stimulation, with a rubber hand illusion based on active and passive movements. We examined the question of which combinations of sensory and motor cues are the most potent in inducing the illusion by subjective ratings and an objective measure (proprioceptive drift). In particular, we were interested in whether the combination of afferent and efferent signals in active movements results in the same illusion as in the purely passive modes. Our results show that the illusion is equally strong in all three cases. This demonstrates that different combinations of sensory input can lead to a very similar phenomenological experience and indicates that the illusion can be induced by any combination of multisensory information. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Understanding human perception by human-made illusions.

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Carbon, Claus-Christian

2014-01-01

IT MAY BE FUN TO PERCEIVE ILLUSIONS, BUT THE UNDERSTANDING OF HOW THEY WORK IS EVEN MORE STIMULATING AND SUSTAINABLE: They can tell us where the limits and capacity of our perceptual apparatus are found-they can specify how the constraints of perception are set. Furthermore, they let us analyze the cognitive sub-processes underlying our perception. Illusions in a scientific context are not mainly created to reveal the failures of our perception or the dysfunctions of our apparatus, but instead point to the specific power of human perception. The main task of human perception is to amplify and strengthen sensory inputs to be able to perceive, orientate and act very quickly, specifically and efficiently. The present paper strengthens this line of argument, strongly put forth by perceptual pioneer Richard L. Gregory (e.g., Gregory, 2009), by discussing specific visual illusions and how they can help us to understand the magic of perception.

Creating standards: Creating illusions?

DEFF Research Database (Denmark)

Linneberg, Mai Skjøtt

written standards may open up for the creation of illusions. These are created when written standards' content is not in accordance with the perception standard adopters and standard users have of the specific practice phenomenon's content. This general theoretical argument is exemplified by the specific...

Effectiveness of optical illusions 
applied on a single composite resin veneer for the diastema closure 
of maxillary central incisors.

Science.gov (United States)

Katsarou, Thomai; Antoniadou, Maria; Papazoglou, Efstratios

To assess the esthetic effectiveness of four illusion techniques applied to a composite resin veneer for diastema closure between maxillary central incisors. An acrylic model with six natural maxillary anterior teeth was fabricated with a 2-mm diastema between the central incisors. Resin veneers were constructed on the left central incisor and the following cases were derived: V0: no veneer; V1: veneer without optical illusion features; V2: veneer with centralized interproximal ridges; V3: veneer with curved incisal edges; V4: veneer with gray pigment mesially/distally; V5: veneer with gray pigment on the developmental lobes. Digital printed photos of the models (13.2 x 17.8 cm, and 6.1 x 8 cm), with low, medium, and high smile lines and without a smile line (processed by Adobe Photoshop CS6) were shown to three groups of people (faculty members, senior undergraduate students, and patients; n = 25/group) for them to assess the overall size and width of the two central incisors. The results were analyzed by Pearson's and chi-square goodness of fit tests. There was no significant influence in the estimation of the two central incisors as being the same size, according to the technique used (P = 0.869) and group of evaluators (P = 0.209). The estimated probability of assessing the tested incisor as wider was indicatively lower in V2 compared to V1 (adjusted odds ratio = 0.59; P = 0.088). The height of the smile line affected the evaluation of the veneers only in the large-sized photos. No interference is the best esthetic decision concerning a 2-mm diastema closure when restoring only one central incisor with a laminate veneer. The next best option is to deliver a veneer with centralized interproximal ridges.

Positive Illusions in Adolescents: The Relationship between Academic Self-Enhancement and Depressive Symptomatology

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Noble, Rick N.; Heath, Nancy L.; Toste, Jessica R.

2011-01-01

Positive illusions are systematically inflated self-perceptions of competence, and are frequently seen in areas of great difficulty. Although these illusions have been extensively documented in children and adults, their role in typical adolescent emotion regulation is unclear. This study investigated the relationship between positive illusions,…

The role of haptic versus visual volume cues in the size-weight illusion.

Science.gov (United States)

Ellis, R R; Lederman, S J

1993-03-01

Three experiments establish the size-weight illusion as a primarily haptic phenomenon, despite its having been more traditionally considered an example of vision influencing haptic processing. Experiment 1 documents, across a broad range of stimulus weights and volumes, the existence of a purely haptic size-weight illusion, equal in strength to the traditional illusion. Experiment 2 demonstrates that haptic volume cues are both sufficient and necessary for a full-strength illusion. In contrast, visual volume cues are merely sufficient, and produce a relatively weaker effect. Experiment 3 establishes that congenitally blind subjects experience an effect as powerful as that of blindfolded sighted observers, thus demonstrating that visual imagery is also unnecessary for a robust size-weight illusion. The results are discussed in terms of their implications for both sensory and cognitive theories of the size-weight illusion. Applications of this work to a human factors design and to sensor-based systems for robotic manipulation are also briefly considered.

Translational illusion of acoustic sources by transformation acoustics.

Science.gov (United States)

Sun, Fei; Li, Shichao; He, Sailing

2017-09-01

An acoustic illusion of creating a translated acoustic source is designed by utilizing transformation acoustics. An acoustic source shifter (ASS) composed of layered acoustic metamaterials is designed to achieve such an illusion. A practical example where the ASS is made with naturally available materials is also given. Numerical simulations verify the performance of the proposed device. The designed ASS may have some applications in, e.g., anti-sonar detection.

Forward Association, Backward Association, and the False-Memory Illusion

Science.gov (United States)

Brainerd, C. J.; Wright, Ron

2005-01-01

In the Deese-Roediger-McDermott false-memory illusion, forward associative strength (FAS) is unrelated to the strength of the illusion; this is puzzling, because high-FAS lists ought to share more semantic features with critical unpresented words than should low-FAS lists. The authors show that this null result is probably a truncated range…

Positive illusions about a partner's physical attractiveness and relationship quality

NARCIS (Netherlands)

Barelds, Dick P. H.; Dijkstra, Pieternel

The present research examined the existence of positive illusions about a partner's physical attractiveness and its relations to relationship quality. Positive illusions were assumed to exist when individuals rated their partner as more attractive than their partner rated him or herself. In two

Analysis and explanation of the Thiéry-Wundt illusion.

Science.gov (United States)

Day, Ross H; Kimm, Andrew C

2010-01-01

The midpoint of the axis of bisection in a triangle appears to be displaced toward the apex so that the apical extent seems to be shorter than the basal extent, an effect originally reported in 1895 by Thiéry and later in 1898 by Wundt and, therefore, referred to here as the Thiéry-Wundt illusion. Following a demonstration strongly suggesting that the illusion is yet another version of the Müller-Lyer effect in a stimulus figure with inward-directed angles, four exploratory experiments designed to throw more light on this group of illusions are reported. The first showed that the effect occurs in an open angle, between converging lines that do not meet to form an apex, between converging stepped lines, and when one of the converging lines is removed, leaving a single oblique line. The other three experiments showed that the illusion also occurs in an open semicircle and a rectangular bracket, is weakened by the addition of a complete or partial baseline to form a triangle, and weakly but reliably when the angle is minimally formed from dots marking the ends of oblique lines. On the basis of these data, Judd's version of the conventional Müller-Lyer figure, and informal but easily repeatable observations, it is concluded that the Thiéry-Wundt illusion is, like other variants of the Müller-Lyer group of illusions, due to a process of directional biasing-an extension of the concept of biasing proposed originally by Morgan et al (1990, Vision Research 30 1793 1810).

The rubber hand illusion increases heat pain threshold.

Science.gov (United States)

Hegedüs, G; Darnai, G; Szolcsányi, T; Feldmann, Á; Janszky, J; Kállai, J

2014-09-01

Accumulating evidence shows that manipulations of cortical body representation, for example, by simply viewing one's own body, can relieve pain in healthy subjects. Despite the widespread use of the rubber hand illusion (RHI) as an effective experimental tool for the manipulation of bodily awareness, previous studies examining the analgesic effect of the RHI have produced conflicting results. We used noxious heat stimuli to induce finger pain in 29 healthy subjects, and we recorded the participants' pain thresholds and subjective pain ratings during the RHI and during the control conditions. Two control conditions were included in our experiment - a standard one with reduced illusion strength (asynchronous stroking control) and an additional one in which the participants viewed their own hand. Raw data showed that both the RHI and the vision of the own hand resulted in slightly higher pain thresholds than the asynchronous stroking control (illusion: 47.79 °C; own-hand: 47.99 °C; asynchronous: 47.52 °C). After logarithmic transformation to achieve normality, paired t-tests revealed that both increases in pain threshold were significant (illusion/asynchronous: p = 0.036; own-hand/asynchronous: p = 0.007). In contrast, there was no significant difference in pain threshold between the illusion and the own-hand conditions (p = 0.656). Pain rating scores were not log-normal, and Wilcoxon singed-rank tests found no significant differences in pain ratings between the study conditions. The RHI increases heat pain threshold and the analgesic effect of the RHI is comparable with that of seeing one's own hand. The latter finding may have clinical implications. © 2014 European Pain Federation - EFIC®

The self is an illusion: a conceptual framework for psychotherapy.

Science.gov (United States)

Stankevicius, Steve

2017-06-01

To explain the illusory nature of the self and explore its implications for psychotherapy. Our usual experience of the self is an illusion. Rather than a discrete entity, it is a network of processes that maintains apparent irreducible unity via alterations of perceptions, beliefs, intentions and memories. By providing an efficient summary of an individual and its surroundings, the self-illusion allows one to predict, experience and interact with the world efficiently. Targeting mechanisms that preserve the self-illusion could provide a focus for psychotherapy. Viewing the self as a complex network offers a valuable conceptual framework for psychotherapy.

The hollow-face illusion: object-specific knowledge, general assumptions or properties of the stimulus?

Science.gov (United States)

Hill, Harold; Johnston, Alan

2007-01-01

The hollow-face illusion, in which a mask appears as a convex face, is a powerful example of binocular depth inversion occurring with a real object under a wide range of viewing conditions. Explanations of the illusion are reviewed and six experiments reported. In experiment 1 the detrimental effect of figural inversion, evidence for the importance of familiarity, was found for other oriented objects. The inversion effect held for masks lit from the side (experiment 2). The illusion was stronger for a mask rotated by 90 degrees lit from its forehead than from its chin, suggesting that familiar patterns of shading enhance the illusion (experiment 2). There were no effects of light source visibility or any left/right asymmetry (experiment 3). In experiments 4-6 we used a 'virtual' hollow face, with illusion strength quantified by the proportion of noise texture needed to eliminate the illusion. Adding characteristic surface colour enhanced the illusion, consistent with the familiar face pigmentation outweighing additional bottom-up cues (experiment 4). There was no difference between perspective and orthographic projection. Photographic negation reduced, but did not eliminate, the illusion, suggesting shading is important but not essential (experiment 5). Absolute depth was not critical, although a shallower mask was given less extreme convexity ratings (experiment 6). We argue that the illusion arises owing to a convexity preference when the raw data have ambiguous interpretations. However, using a familiar object with typical orientation, shading, and pigmentation greatly enhances the effect.

The Rubber Hand Illusion paradigm as a sensory learning process in patients with schizophrenia.

Science.gov (United States)

Lev-Ari, L; Hirschmann, S; Dyskin, O; Goldman, O; Hirschmann, I

2015-10-01

The Rubber Hand Illusion (RHI) has previously been used to depict the hierarchy between visual, tactile and perceptual stimuli. Studies on schizophrenia inpatients (SZs) have found mixed results in the ability to first learn the illusion, and have yet to explain the learning process involved. This study's aim was two-fold: to examine the learning process of the RHI in SZs and healthy controls over time, and to better understand the relationship between psychotic symptoms and the RHI. Thirty schizophrenia inpatients and 30 healthy controls underwent five different trials of the RHI over a two-week period. As has been found in previous studies, SZs felt the initial illusion faster than healthy controls did, but their learning process throughout the trials was inconsistent. Furthermore, for SZs, no correlations between psychotic symptoms and the learning of the illusion emerged. Healthy individuals show a delayed reaction to first feeling the illusion (due to latent inhibition), but easily learn the illusion over time. For SZs, both strength of the illusion and the ability to learn the illusion over time are inconsistent. The cognitive impairment in SZ impedes the learning process of the RHI, and SZs are unable to utilize the repetition of the process as healthy individuals can. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Action observation with kinesthetic illusion can produce human motor plasticity.

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Nojima, Ippei; Koganemaru, Satoko; Kawamata, Toshio; Fukuyama, Hidenao; Mima, Tatsuya

2015-06-01

After watching sports, people often feel as if their sports skills might have been improved, even without any actual training. On some occasions, this motor skill learning through observation actually occurs. This phenomenon may be due to the fact that both action and action observation (AO) can activate shared cortical areas. However, the neural basis of performance gain through AO has not yet been fully clarified. In the present study, we used transcranial magnetic stimulation to investigate whether primary motor cortex (M1) plasticity is a physiological substrate of AO-induced performance gain and whether AO itself is sufficient to change motor performance. The excitability of M1, especially that of its intracortical excitatory circuit, was enhanced after and during AO with kinesthetic illusion but not in interventions without this illusion. Moreover, behavioral improvement occurred only after AO with kinesthetic illusion, and a significant correlation existed between the performance gain and the degree of illusion. Our findings indicated that kinesthetic illusion is an essential component of the motor learning and M1 plasticity induced by AO, and this insight may be useful for the strategic rehabilitation of stroke patients. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

An Adaptation-Induced Repulsion Illusion in Tactile Spatial Perception

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Lux Li

2017-06-01

Full Text Available Following focal sensory adaptation, the perceived separation between visual stimuli that straddle the adapted region is often exaggerated. For instance, in the tilt aftereffect illusion, adaptation to tilted lines causes subsequently viewed lines with nearby orientations to be perceptually repelled from the adapted orientation. Repulsion illusions in the nonvisual senses have been less studied. Here, we investigated whether adaptation induces a repulsion illusion in tactile spatial perception. In a two-interval forced-choice task, participants compared the perceived separation between two point-stimuli applied on the forearms successively. Separation distance was constant on one arm (the reference and varied on the other arm (the comparison. In Experiment 1, we took three consecutive baseline measurements, verifying that in the absence of manipulation, participants’ distance perception was unbiased across arms and stable across experimental blocks. In Experiment 2, we vibrated a region of skin on the reference arm, verifying that this focally reduced tactile sensitivity, as indicated by elevated monofilament detection thresholds. In Experiment 3, we applied vibration between the two reference points in our distance perception protocol and discovered that this caused an illusory increase in the separation between the points. We conclude that focal adaptation induces a repulsion aftereffect illusion in tactile spatial perception. The illusion provides clues as to how the tactile system represents spatial information. The analogous repulsion aftereffects caused by adaptation in different stimulus domains and sensory systems may point to fundamentally similar strategies for dynamic sensory coding.

Positive illusions about one's partner's physical attractiveness.

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Barelds-Dijkstra, Pieternel; Barelds, Dick P H

2008-03-01

This study examined couples' ratings of self and partner physical attractiveness. On the basis of the theory of positive illusions, it was expected that individuals would rate their partners as more attractive than their partners would rate themselves. Both members of 93 heterosexual couples, with a mean relationship length of about 14 years, provided ratings of both their own and their partner's physical attractiveness. Results support the theory that individuals hold positive illusions about their partner's physical attractiveness. Implications of these results in terms of relationship-enhancing biases are discussed.

The multiple-faces configuration illusion in schizophrenic patients

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Simas, Maria Lucia de Bustamante; Rocha, Christiane Delusia de Oliveira; Sedycias, Rafael Freitas Modesto; Amaral, Viviane Ferreira do; Menezes, Felipe Schuler de

2008-01-01

The Multiple-Faces Configuration Illusion is observed by staring at a black dot while paying attention to a face in the peripheral visual field (Simas, 2000). Changes of facial expressions, movements, depth (EMF) or different face identities (MF) are observed in this illusion. Forty participants took part in the study: 20 outpatients diagnosed with schizophrenia, and 20 people helping friends or relatives in a hospital clinic. The face-stimulus was placed in a partition stand and participants...

English: Illusion vs. Reality.

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Knappe, Shirley; Hall, Peggy

This teaching guide covers a study of significant literary works that deal with man's capacity for illusion and self-deception in his quest for identification and fulfillment. The guide lists Performance Objectives, Course Content, Teaching Strategies, Learning Activities, Student Resources, and Teacher Resources. The subject matter range is (1)…

Quadri-stability of a spatially ambiguous auditory illusion

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Constance May Bainbridge

2015-01-01

Full Text Available In addition to vision, audition plays an important role in sound localization in our world. One way we estimate the motion of an auditory object moving towards or away from us is from changes in volume intensity. However, the human auditory system has unequally distributed spatial resolution, including difficulty distinguishing sounds in front versus behind the listener. Here, we introduce a novel quadri-stable illusion, the Transverse-and-Bounce Auditory Illusion, which combines front-back confusion with changes in volume levels of a nonspatial sound to create ambiguous percepts of an object approaching and withdrawing from the listener. The sound can be perceived as traveling transversely from front to back or back to front, or bouncing to remain exclusively in front of or behind the observer. Here we demonstrate how human listeners experience this illusory phenomenon by comparing ambiguous and unambiguous stimuli for each of the four possible motion percepts. When asked to rate their confidence in perceiving each sound’s motion, participants reported equal confidence for the illusory and unambiguous stimuli. Participants perceived all four illusory motion percepts, and could not distinguish the illusion from the unambiguous stimuli. These results show that this illusion is effectively quadri-stable. In a second experiment, the illusory stimulus was looped continuously in headphones while participants identified its perceived path of motion to test properties of perceptual switching, locking, and biases. Participants were biased towards perceiving transverse compared to bouncing paths, and they became perceptually locked into alternating between front-to-back and back-to-front percepts, perhaps reflecting how auditory objects commonly move in the real world. This multi-stable auditory illusion opens opportunities for studying the perceptual, cognitive, and neural representation of objects in motion, as well as exploring multimodal perceptual

The snow tire illusion: Different levels of perceptual assimilation across a single stimulus configuration.

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Gulan, Tanja; Valerjev, Pavle; Dujmović, Marin

2018-02-12

While observing a specific traffic sign in the field, we noticed an apparent distortion of size and shape of the circle that contained the sign. This novel illusion manifests as a distortion of the horizontal compared to the vertical dimension of the sign. The illusion seems to be underlined by similar mechanisms to those in the Delboeuf illusion. The aim of our study was to determine the existence and magnitude of the snow tire illusion. We conducted two experiments using the method of constant stimuli. The first experiment was conducted on the standard sign, while in the second, the stimuli were rotated 90° counterclockwise. Both experiments consisted of three conditions: the snow tire, the ellipse, and the simple circle (control) conditions. The data showed a robust illusion effect for both the standard and rotated sign compared to the control condition, with a large majority of participants experiencing the illusion. The snow tire illusion seems to be a combination of assimilation mechanisms of different magnitudes. The assimilation is larger for one dimension of the sign, thus producing the shape distortion. The illusion may be a manifestation of a thus far undocumented non-uniform effect of assimilation on perceived size and shape. © 2018 The Institute of Psychology, Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

Parietal disruption alters audiovisual binding in the sound-induced flash illusion.

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Kamke, Marc R; Vieth, Harrison E; Cottrell, David; Mattingley, Jason B

2012-09-01

Selective attention and multisensory integration are fundamental to perception, but little is known about whether, or under what circumstances, these processes interact to shape conscious awareness. Here, we used transcranial magnetic stimulation (TMS) to investigate the causal role of attention-related brain networks in multisensory integration between visual and auditory stimuli in the sound-induced flash illusion. The flash illusion is a widely studied multisensory phenomenon in which a single flash of light is falsely perceived as multiple flashes in the presence of irrelevant sounds. We investigated the hypothesis that extrastriate regions involved in selective attention, specifically within the right parietal cortex, exert an influence on the multisensory integrative processes that cause the flash illusion. We found that disruption of the right angular gyrus, but not of the adjacent supramarginal gyrus or of a sensory control site, enhanced participants' veridical perception of the multisensory events, thereby reducing their susceptibility to the illusion. Our findings suggest that the same parietal networks that normally act to enhance perception of attended events also play a role in the binding of auditory and visual stimuli in the sound-induced flash illusion. Copyright © 2012 Elsevier Inc. All rights reserved.

The Application of Visual Illusion in the Visual Communication Design

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Xin, Tao; You Ye, Han

2018-03-01

With the development of our national reform, opening up and modernization, the science and technology has also been well developed and it has been applied in every wall of life, the development of visual illusion industry is represented in the widespread use of advanced technology in it. Ultimately, the visual illusion is a phenomenon, it should be analyzed from the angles of physics and philosophy. The widespread application of visual illusion not only can improve the picture quality, but also could maximize peoples’ sense degree through the visual communication design works, expand people’s horizons and promote the diversity of visual communication design works.

BETWEEN KNOWING AND BELIEVING: SALVAGING ILLUSION'S RIGHTFUL PLACE IN PSYCHOANALYSIS.

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Tuch, Richard

2016-01-01

Illusion has historically received insufficient psychoanalytic attention, even though it plays an indispensable and adaptive role that helps protect individuals from becoming traumatized by the most psychically noxious aspects of reality. Trauma is mitigated by an individual's knowing about the existence of such realities yet simultaneously believing them non-existent, with neither position granted exclusivity. Psychoanalytic theory is surprisingly predicated on the employment of illusions that picture an individual capable of controlling the potentially traumatic actions of others, just so long as the individual effectively manages his own intrapsychic processes (wishes, fantasies, impulses, etc.). The role of illusion in everyday life is highlighted. © 2016 The Psychoanalytic Quarterly, Inc.

Open active cloaking and illusion devices for the Laplace equation

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Ma, Qian; Yang, Fan; Jin, Tian Yu; Mei, Zhong Lei; Cui, Tie Jun

2016-01-01

We propose open active cloaking and illusion devices for the Laplace equation. Compared with the closed configurations of active cloaking and illusion devices, we focus on improving the distribution schemes for the controlled sources, which do not have to surround the protected object strictly. Instead, the controlled sources can be placed in several small discrete clusters, and produce the desired voltages along the controlled boundary, to actively hide or disguise the protected object. Numerical simulations are performed with satisfactory results, which are further validated by experimental measurements. The open cloaking and illusion devices have many advantages over the closed configurations in various potential applications. (paper)

Analyzing Double Image Illusion through Double Indiscernibility and Lattice Theory

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Kohei Sonoda

2011-10-01

Full Text Available The figure-ground division plays a fundamental role in all image perceptions. Although there are a lot of studies about extraction of a figure such as detection of edges or grouping of texture, there are few discussions about a relationship between obtained figure and ground. We focused on double image illusions having two complementary relationships be- tween figure and ground and analyzed them. We divided the double image illusions according to two different interpretations and using these divisions we extracted and analyzed their logical structures by lattices derived from rough sets that we had developed. As a result we discovered unusual logical structures in double image illusions.

The illusion of owning a third arm.

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Arvid Guterstam

Full Text Available Could it be possible that, in the not-so-distant future, we will be able to reshape the human body so as to have extra limbs? A third arm helping us out with the weekly shopping in the local grocery store, or an extra artificial limb assisting a paralysed person? Here we report a perceptual illusion in which a rubber right hand, placed beside the real hand in full view of the participant, is perceived as a supernumerary limb belonging to the participant's own body. This effect was supported by questionnaire data in conjunction with physiological evidence obtained from skin conductance responses when physically threatening either the rubber hand or the real one. In four well-controlled experiments, we demonstrate the minimal required conditions for the elicitation of this "supernumerary hand illusion". In the fifth, and final experiment, we show that the illusion reported here is qualitatively different from the traditional rubber hand illusion as it is characterised by less disownership of the real hand and a stronger feeling of having two right hands. These results suggest that the artificial hand 'borrows' some of the multisensory processes that represent the real hand, leading to duplication of touch and ownership of two right arms. This work represents a major advance because it challenges the traditional view of the gross morphology of the human body as a fundamental constraint on what we can come to experience as our physical self, by showing that the body representation can easily be updated to incorporate an additional limb.

The Honeycomb illusion: Uniform textures not perceived as such

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Marco Bertamini

2016-07-01

Full Text Available We present a series of patterns, in which texture is perceived differently at fixation in comparison to the periphery, such that a physically uniform stimulus yields a nonuniform percept. We call this the Honeycomb illusion, and we discuss it in relation to the similar Extinction illusion (Ninio & Stevens, 2000. The effect remains strong despite multiple fixations, dynamic changes, and manipulations of the size of texture elements. We discuss the phenomenon in relation to how vision achieves a detailed and stable representation of the environment despite changes in retinal spatial resolution and dramatic changes across saccades. The Honeycomb illusion complements previous related observations in suggesting that this representation is not necessarily based on multiple fixations (i.e., memory or on extrapolation from information available to central vision.

Pathological gamblers are more vulnerable to the illusion of control in a standard associative learning task

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Cristina eOrgaz

2013-06-01

Full Text Available An illusion of control is said to occur when a person believes that he or she controls an outcome that is uncontrollable. Pathological gambling has often been related to an illusion of control, but the assessment of the illusion has generally used introspective methods in domain-specific (i.e., gambling situations. The illusion of control of pathological gamblers, however, could be a more general problem, affecting other aspects of their daily life. Thus, we tested them using a standard associative learning task which is known to produce illusions of control in most people under certain conditions. The results showed that the illusion was significantly stronger in pathological gamblers than in a control undiagnosed sample. This suggests (a that the experimental tasks used in basic associative learning research could be used to detect illusions of control in gamblers in a more indirect way, as compared to introspective and domain-specific questionnaires; and (b, that in addition to gambling-specific problems, pathological gamblers may have a higher-than-normal illusion of control in their daily life.

Sleep dissolves illusion: sleep withstands learning of visuo-tactile-proprioceptive integration induced by repeated days of rubber hand illusion training.

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Motoyasu Honma

Full Text Available Multisensory integration is a key factor in establishing bodily self-consciousness and in adapting humans to novel environments. The rubber hand illusion paradigm, in which humans can immediately perceive illusory ownership to an artificial hand, is a traditional technique for investigating multisensory integration and the feeling of illusory ownership. However, the long-term learning properties of the rubber hand illusion have not been previously investigated. Moreover, although sleep contributes to various aspects of cognition, including learning and memory, its influence on illusory learning of the artificial hand has not yet been assessed. We determined the effects of daily repetitive training and sleep on learning visuo-tactile-proprioceptive sensory integration and illusory ownership in healthy adult participants by using the traditional rubber hand illusion paradigm. Subjective ownership of the rubber hand, proprioceptive drift, and galvanic skin response were measured to assess learning indexes. Subjective ownership was maintained and proprioceptive drift increased with daily training. Proprioceptive drift, but not subjective ownership, was significantly attenuated after sleep. A significantly greater reduction in galvanic skin response was observed after wakefulness compared to after sleep. Our results suggest that although repetitive rubber hand illusion training facilitates multisensory integration and physiological habituation of a multisensory incongruent environment, sleep corrects illusional integration and habituation based on experiences in a multisensory incongruent environment. These findings may increase our understanding of adaptive neural processes to novel environments, specifically, bodily self-consciousness and sleep-dependent neuroplasticity.

Sleep dissolves illusion: sleep withstands learning of visuo-tactile-proprioceptive integration induced by repeated days of rubber hand illusion training.

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Honma, Motoyasu; Yoshiike, Takuya; Ikeda, Hiroki; Kim, Yoshiharu; Kuriyama, Kenichi

2014-01-01

Multisensory integration is a key factor in establishing bodily self-consciousness and in adapting humans to novel environments. The rubber hand illusion paradigm, in which humans can immediately perceive illusory ownership to an artificial hand, is a traditional technique for investigating multisensory integration and the feeling of illusory ownership. However, the long-term learning properties of the rubber hand illusion have not been previously investigated. Moreover, although sleep contributes to various aspects of cognition, including learning and memory, its influence on illusory learning of the artificial hand has not yet been assessed. We determined the effects of daily repetitive training and sleep on learning visuo-tactile-proprioceptive sensory integration and illusory ownership in healthy adult participants by using the traditional rubber hand illusion paradigm. Subjective ownership of the rubber hand, proprioceptive drift, and galvanic skin response were measured to assess learning indexes. Subjective ownership was maintained and proprioceptive drift increased with daily training. Proprioceptive drift, but not subjective ownership, was significantly attenuated after sleep. A significantly greater reduction in galvanic skin response was observed after wakefulness compared to after sleep. Our results suggest that although repetitive rubber hand illusion training facilitates multisensory integration and physiological habituation of a multisensory incongruent environment, sleep corrects illusional integration and habituation based on experiences in a multisensory incongruent environment. These findings may increase our understanding of adaptive neural processes to novel environments, specifically, bodily self-consciousness and sleep-dependent neuroplasticity.

Early and late beta-band power reflect audiovisual perception in the McGurk illusion.

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Roa Romero, Yadira; Senkowski, Daniel; Keil, Julian

2015-04-01

The McGurk illusion is a prominent example of audiovisual speech perception and the influence that visual stimuli can have on auditory perception. In this illusion, a visual speech stimulus influences the perception of an incongruent auditory stimulus, resulting in a fused novel percept. In this high-density electroencephalography (EEG) study, we were interested in the neural signatures of the subjective percept of the McGurk illusion as a phenomenon of speech-specific multisensory integration. Therefore, we examined the role of cortical oscillations and event-related responses in the perception of congruent and incongruent audiovisual speech. We compared the cortical activity elicited by objectively congruent syllables with incongruent audiovisual stimuli. Importantly, the latter elicited a subjectively congruent percept: the McGurk illusion. We found that early event-related responses (N1) to audiovisual stimuli were reduced during the perception of the McGurk illusion compared with congruent stimuli. Most interestingly, our study showed a stronger poststimulus suppression of beta-band power (13-30 Hz) at short (0-500 ms) and long (500-800 ms) latencies during the perception of the McGurk illusion compared with congruent stimuli. Our study demonstrates that auditory perception is influenced by visual context and that the subsequent formation of a McGurk illusion requires stronger audiovisual integration even at early processing stages. Our results provide evidence that beta-band suppression at early stages reflects stronger stimulus processing in the McGurk illusion. Moreover, stronger late beta-band suppression in McGurk illusion indicates the resolution of incongruent physical audiovisual input and the formation of a coherent, illusory multisensory percept. Copyright © 2015 the American Physiological Society.

[Are positive illusions adaptive?: self- and other-rating].

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Toyama, Miki

2008-08-01

The present study investigated the relationship between children's overly positive self-perceptions of their own social competence and mental health. Elementary school students (grades fourth to sixth, n=331) and their homeroom teachers (n=9) participated in the study. The positive illusion was measured by the difference between the self-rating and the other (homeroom teachers) -rating. And, the index of mental health was administered in both self-rating and other (homeroom teachers and same-sex classmates) -rating forms. Positive illusions about children's social competence were positively related to self-ratings of mental health. However, the present study also found detrimental effects of such positive illusions. Children with excessively positive views of their social competence were viewed by teachers and same-sex classmates as significantly more aggressive than those children who showed more evidence of self-devaluation. In addition, children with overly positive self-perceptions were not as accepted by same-sex classmates.

Multisensory Integration in the Virtual Hand Illusion with Active Movement.

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Choi, Woong; Li, Liang; Satoh, Satoru; Hachimura, Kozaburo

2016-01-01

Improving the sense of immersion is one of the core issues in virtual reality. Perceptual illusions of ownership can be perceived over a virtual body in a multisensory virtual reality environment. Rubber Hand and Virtual Hand Illusions showed that body ownership can be manipulated by applying suitable visual and tactile stimulation. In this study, we investigate the effects of multisensory integration in the Virtual Hand Illusion with active movement. A virtual xylophone playing system which can interactively provide synchronous visual, tactile, and auditory stimulation was constructed. We conducted two experiments regarding different movement conditions and different sensory stimulations. Our results demonstrate that multisensory integration with free active movement can improve the sense of immersion in virtual reality.

Mishaps, errors, and cognitive experiences: On the conceptualization of perceptual illusions

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Daniele eZavagno

2015-04-01

Full Text Available Although a visual illusion is often viewed as an amusing trick, for the vision scientist it is a question that demands an answer, which leads to even more questioning. All researchers hold their own chain of questions, the links of which depend on the very theory they adhere to. Perceptual theories are devoted to answering questions concerning sensation and perception, but in doing so they shape concepts such as reality and representation, which necessarily affect the concept of illusion. Here we consider the macroscopic aspects of such concepts in vision sciences from three classic viewpoints – Ecological, Cognitive, Gestalt approaches – as we see this a starting point to understand in which terms illusions can become a tool in the hand of the neuroscientist. In fact, illusions can be effective tools in studying the brain in reference to perception and also to cognition in a much broader sense. A theoretical debate is, however, mandatory, in particular with regards to concepts such as veridicality and representation. Whether a perceptual outcome is considered as veridical or illusory (and, consequently, whether a class of phenomena should be classified as perceptual illusions or not depends on the meaning of such concepts.

La Grande Guerra fra realtà ed illusione: La Grande Illusion e l’immaginario

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Simone Di Blasi

2015-12-01

Full Text Available The aim of this brief essay is to focus on the relation between the meaning of reality and illusion in the movie La Grande Illusion (1937 by Jean Renoir and therefore to find how these ideas of the author may be productive in a thought about the imaginary. After a short look on the movies made at that time on the First World War, there is an overview of the French director poetics, which redefines the conception of the realism, contextualizing its work at the point of convergence of two imaginary “technological lines”, the cinema and the aviation. It follows the analysis of the movie and the illusions, as social largely shared imaginaries, described by the author. In the end it is showed the importance and the of illusion in Renoir’s poetics. Beyond the relationship realityfiction, he thought a dynamic reciprocity among illusion and reality: so that the reality is as “illusion” (a ruled horizon in which it is possible to enjoy a world of play and the illusion as an activity creating contents of “reality”.

Rubber hand illusion under delayed visual feedback.

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Sotaro Shimada

Full Text Available BACKGROUND: Rubber hand illusion (RHI is a subject's illusion of the self-ownership of a rubber hand that was touched synchronously with their own hand. Although previous studies have confirmed that this illusion disappears when the rubber hand was touched asynchronously with the subject's hand, the minimum temporal discrepancy of these two events for attenuation of RHI has not been examined. METHODOLOGY/PRINCIPAL FINDINGS: In this study, various temporal discrepancies between visual and tactile stimulations were introduced by using a visual feedback delay experimental setup, and RHI effects in each temporal discrepancy condition were systematically tested. The results showed that subjects felt significantly greater RHI effects with temporal discrepancies of less than 300 ms compared with longer temporal discrepancies. The RHI effects on reaching performance (proprioceptive drift showed similar conditional differences. CONCLUSIONS/SIGNIFICANCE: Our results first demonstrated that a temporal discrepancy of less than 300 ms between visual stimulation of the rubber hand and tactile stimulation to the subject's own hand is preferable to induce strong sensation of RHI. We suggest that the time window of less than 300 ms is critical for multi-sensory integration processes constituting the self-body image.

Complementarity in false memory illusions.

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Brainerd, C J; Reyna, V F

2018-03-01

For some years, the DRM illusion has been the most widely studied form of false memory. The consensus theoretical interpretation is that the illusion is a reality reversal, in which certain new words (critical distractors) are remembered as though they are old list words rather than as what they are-new words that are similar to old ones. This reality-reversal interpretation is supported by compelling lines of evidence, but prior experiments are limited by the fact that their memory tests only asked whether test items were old. We removed that limitation by also asking whether test items were new-similar. This more comprehensive methodology revealed that list words and critical distractors are remembered quite differently. Memory for list words is compensatory: They are remembered as old at high rates and remembered as new-similar at very low rates. In contrast, memory for critical distractors is complementary: They are remembered as both old and new-similar at high rates, which means that the DRM procedure induces a complementarity illusion rather than a reality reversal. The conjoint recognition model explains complementarity as a function of three retrieval processes (semantic familiarity, target recollection, and context recollection), and it predicts that complementarity can be driven up or down by varying the mix of those processes. Our experiments generated data on that prediction and introduced a convenient statistic, the complementarity ratio, which measures (a) the level of complementarity in memory performance and (b) whether its direction is reality-consistent or reality-reversed. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Combined induction of rubber-hand illusion and out-of-body experiences

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Isadora eOlivé

2012-05-01

Full Text Available The emergence of self-consciousness depends on several processes: those of body ownership, attributing self-identity to the body, and those of self-location, localizing our sense of self. Studies of phenomena like the rubber hand illusion (RHi and out-of-body experience (OBE investigate these processes, respectively for representations of a body-part and the full-body. It is supposed that RHi only target processes related to body-part representations, while OBE only relates to full-body representations. The fundamental question whether the body-part and the full-body illusions relate to each other is nevertheless insufficiently investigated. In search for a link between body-part and full-body illusions in the brain we developed a behavioural task combining adapted versions of the RHi and OBE. Furthermore, for the investigation of this putative link we investigated the role of sensory and motor cues. We established a spatial dissociation between visual and proprioceptive feedback of a hand perceived through virtual reality in rest or action. Two experimental measures were introduced: one for the body-part illusion, the proprioceptive drift of the perceived localisation of the hand, and one for the full-body illusion, the shift in subjective-straight-ahead. In the rest and action conditions it was observed that the proprioceptive drift of the left hand and the shift in subjective-straight-ahead towards the manipulation side are equivalent. The combined effect was dependent on the manipulation of the visual representation of body-parts, rejecting any main or even modulatory role for relevant motor programs. Our study demonstrates for the first time that there is a systematic relationship between the body-part illusion and the full-body illusion, as shown by our measures. This suggests a link between the representations in the brain of a body-part and the full-body, and consequently a common mechanism underpinning both forms of ownership and self-location.

Multisensory Integration in the Virtual Hand Illusion with Active Movement

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Woong Choi

2016-01-01

Full Text Available Improving the sense of immersion is one of the core issues in virtual reality. Perceptual illusions of ownership can be perceived over a virtual body in a multisensory virtual reality environment. Rubber Hand and Virtual Hand Illusions showed that body ownership can be manipulated by applying suitable visual and tactile stimulation. In this study, we investigate the effects of multisensory integration in the Virtual Hand Illusion with active movement. A virtual xylophone playing system which can interactively provide synchronous visual, tactile, and auditory stimulation was constructed. We conducted two experiments regarding different movement conditions and different sensory stimulations. Our results demonstrate that multisensory integration with free active movement can improve the sense of immersion in virtual reality.

Strange-face Illusions During Interpersonal-Gazing and Personality Differences of Spirituality.

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Caputo, Giovanni B

Strange-face illusions are produced when two individuals gaze at each other in the eyes in low illumination for more than a few minutes. Usually, the members of the dyad perceive numinous apparitions, like the other's face deformations and perception of a stranger or a monster in place of the other, and feel a short lasting dissociation. In the present experiment, the influence of the spirituality personality trait on strength and number of strange-face illusions was investigated. Thirty participants were preliminarily tested for superstition (Paranormal Belief Scale, PBS) and spirituality (Spiritual Transcendence Scale, STS); then, they were randomly assigned to 15 dyads. Dyads performed the intersubjective gazing task for 10 minutes and, finally, strange-face illusions (measured through the Strange-Face Questionnaire, SFQ) were evaluated. The first finding was that SFQ was independent of PBS; hence, strange-face illusions during intersubjective gazing are authentically perceptual, hallucination-like phenomena, and not due to superstition. The second finding was that SFQ depended on the spiritual-universality scale of STS (a belief in the unitive nature of life; e.g., "there is a higher plane of consciousness or spirituality that binds all people") and the two variables were negatively correlated. Thus, strange-face illusions, in particular monstrous apparitions, could potentially disrupt binding among human beings. Strange-face illusions can be considered as 'projections' of the subject's unconscious into the other's face. In conclusion, intersubjective gazing at low illumination can be a tool for conscious integration of unconscious 'shadows of the Self' in order to reach completeness of the Self. Copyright © 2017 Elsevier Inc. All rights reserved.

Introducing the White Noise task in childhood: associations between speech illusions and psychosis vulnerability.

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Rimvall, M K; Clemmensen, L; Munkholm, A; Rask, C U; Larsen, J T; Skovgaard, A M; Simons, C J P; van Os, J; Jeppesen, P

2016-10-01

Auditory verbal hallucinations (AVH) are common during development and may arise due to dysregulation in top-down processing of sensory input. This study was designed to examine the frequency and correlates of speech illusions measured using the White Noise (WN) task in children from the general population. Associations between speech illusions and putative risk factors for psychotic disorder and negative affect were examined. A total of 1486 children aged 11-12 years of the Copenhagen Child Cohort 2000 were examined with the WN task. Psychotic experiences and negative affect were determined using the Kiddie-SADS-PL. Register data described family history of mental disorders. Exaggerated Theory of Mind functioning (hyper-ToM) was measured by the ToM Storybook Frederik. A total of 145 (10%) children experienced speech illusions (hearing speech in the absence of speech stimuli), of which 102 (70%) experienced illusions perceived by the child as positive or negative (affectively salient). Experiencing hallucinations during the last month was associated with affectively salient speech illusions in the WN task [general cognitive ability: adjusted odds ratio (aOR) 2.01, 95% confidence interval (CI) 1.03-3.93]. Negative affect, both last month and lifetime, was also associated with affectively salient speech illusions (aOR 2.01, 95% CI 1.05-3.83 and aOR 1.79, 95% CI 1.11-2.89, respectively). Speech illusions were not associated with delusions, hyper-ToM or family history of mental disorders. Speech illusions were elicited in typically developing children in a WN-test paradigm, and point to an affective pathway to AVH mediated by dysregulation in top-down processing of sensory input.

Body ownership and the four-hand illusion.

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Chen, Wen-Yeo; Huang, Hsu-Chia; Lee, Yen-Tung; Liang, Caleb

2018-02-01

Recent studies of the rubber hand illusion (RHI) have shown that the sense of body ownership is constrained by several factors and yet is still very flexible. However, exactly how flexible is our sense of body ownership? In this study, we address this issue by investigating the following question: is it possible that one may have the illusory experience of owning four hands? Under visual manipulation, the participant adopted the experimenter's first-person perspective (1PP) as if it was his/her own. Sitting face to face, the participant saw four hands-the experimenter's two hands from the adopted 1PP together with the subject's own two hands from the adopted third-person perspective (3PP). We found that: (1) the four-hand illusion did not occur in the passive four-hand condition. (2) In the active four-hand condition, the participants tapped their index fingers, imitated by the experimenter. When tactile stimulations were not provided, the key illusion was not induced, either. (3) Strikingly, once all four hands began to act with the same pattern and received synchronous tactile stimulations at the same time, many participants felt as if they had two more hands. These results show that the sense of body ownership is much more flexible than most researchers have suggested.

Corporeal illusions in chronic spinal cord injuries.

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Scandola, Michele; Aglioti, Salvatore Maria; Avesani, Renato; Bertagnoni, Gianettore; Marangoni, Anna; Moro, Valentina

2017-03-01

While several studies have investigated corporeal illusions in patients who have suffered from a stroke or undergone an amputation, only anecdotal or single case reports have explored this phenomenon after spinal cord injury. Here we examine various different types of bodily misperceptions in a comparatively large group of 49 people with spinal cord injury in the post-acute and chronic phases after the traumatic lesion onset. An extensive battery of questionnaires concerning a variety of body related feelings was administered and the results were correlated to the main clinical variables. Six different typologies of Corporeal Illusion emerged: Sensations of Body Loss; Body-Part Misperceptions; Somatoparaphrenia-like sensations; Disownership-like sensations; Illusory motion and Misoplegia. All of these (with the exception of Misoplegia) are modulated by clinical variables such as pain (visceral, neuropathic and musculoskeletal), completeness of the lesion, level of the lesion and the length of time since lesion onset. In contrast, no significant correlations between bodily illusions and personality variables were found. These results support data indicating that at least some cognitive functions (in particular the body, action and space representations) are embodied and that somatosensory input and motor output may be necessary to build and maintain a typical self-body representation. Copyright © 2017 Elsevier Inc. All rights reserved.

Illusion as a Basic Psychic Principle: Winnicott, Freud, Oedipus, and Trump.

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Seligman, Stephen

2018-04-01

Illusion can be viewed as a creative engagement with the world, and as a central psychic motivation and capacity, rather than as a form of self-deception. Winnicott and other Middle Group writers have understood integrative, imaginative illusion as an essential part of healthy living and psychosocial development. As such, it emerges and presents itself in a variety of ways, in transaction with the realities that support or degrade it. In its absence, varied difficulties in living ensue. To elaborate and illustrate this conceptualization, Freud's notion that the oedipus complex is resolved is reconsidered as a creative misreading of Sophocles' Oedipus trilogy, one based on the plausible illusion of a civilizing psychosocial development that would serve as a protective bastion against his experience of the political chaos and violence of the first decades of twentieth-century European history. Finally, the place of illusion and disillusionment among those most disillusioned by the recent election of Donald Trump in the United States is considered in relation to the recent right-wing populist turn.

Removal of proprioception by BCI raises a stronger body ownership illusion in control of a humanlike robot.

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Alimardani, Maryam; Nishio, Shuichi; Ishiguro, Hiroshi

2016-09-22

Body ownership illusions provide evidence that our sense of self is not coherent and can be extended to non-body objects. Studying about these illusions gives us practical tools to understand the brain mechanisms that underlie body recognition and the experience of self. We previously introduced an illusion of body ownership transfer (BOT) for operators of a very humanlike robot. This sensation of owning the robot's body was confirmed when operators controlled the robot either by performing the desired motion with their body (motion-control) or by employing a brain-computer interface (BCI) that translated motor imagery commands to robot movement (BCI-control). The interesting observation during BCI-control was that the illusion could be induced even with a noticeable delay in the BCI system. Temporal discrepancy has always shown critical weakening effects on body ownership illusions. However the delay-robustness of BOT during BCI-control raised a question about the interaction between the proprioceptive inputs and delayed visual feedback in agency-driven illusions. In this work, we compared the intensity of BOT illusion for operators in two conditions; motion-control and BCI-control. Our results revealed a significantly stronger BOT illusion for the case of BCI-control. This finding highlights BCI's potential in inducing stronger agency-driven illusions by building a direct communication between the brain and controlled body, and therefore removing awareness from the subject's own body.

The Wundt-Jastrow illusion in the study of spatial hemi-inattention.

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Massironi, M; Antonucci, G; Pizzamiglio, L; Vitale, M V; Zoccolotti, P

1988-01-01

A new test to detect unilateral neglect was devised using a modified version of the Wundt-Jastrow area illusion. The test was given to three groups of subjects: left brain damaged (LBD), right brain damaged (RBD) patients and controls. Of RBD patients, 40.4% but no LBD patient or control, showed responses inconsistent with the visual illusion when the determinant features of the illusion pointed to the left visual field. These unexpected responses were highly related to a clinical evaluation of the severity of the hemi-inattention disorder. The sensitivity of this test and of other standard measures of hemi-neglect were compared. The possibility of identifying qualitatively different forms of hemi-neglect was also discussed.

The illusion of parental celibacy. A necessary stage in adolescent development.

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Shopper, Moisy

2002-01-01

The paper begins by reviewing Freud's case history of Dora and emphasizing her involvement in and overstimulation by her parents' sexual behavior. This markedly interfered with her ability to desexualize her relationship with them. As a result she was unable to develop the illusion of parental celibacy, which I postulate is an important and necessary defensive stage in normal adolescence. This illusion facilitates the desexualization of the adolescent's relationship to the parents and so contributes to separation from them and the seeking of non-incestuous sexual outlets. The disruption of this illusion of parental celibacy by parental sex education, or by the complications of parental divorce may contribute significantly to the development of adolescent psychopathology. Clinical vignettes are presented.

Second-Order Footsteps Illusions

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Akiyoshi Kitaoka

2015-12-01

Full Text Available In the “footsteps illusion”, light and dark squares travel at constant speed across black and white stripes. The squares appear to move faster and slower as their contrast against the stripes varies. We now demonstrate some second-order footsteps illusions, in which all edges are defined by colors or textures—even though luminance-based neural motion detectors are blind to such edges.

Approaching Stan Laurel's illusion: the self-induced rubber hand phenomenon.

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Neuf, Hartmut; Hamburger, Kai

2013-01-01

The classical rubber hand illusion is induced by an experimenter (eg stimulation with a brush) and usually realized with some sort of visual occlusion. Here, we demonstrate a new phenomenon: the self-induced rubber hand illusion. It is possible to elicit the feeling of a third hand without any help from an experimenter and under conditions of no occlusion. The findings are discussed within the context of neural plasticity.

Does affective touch influence the virtual reality full body illusion?

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de Jong, Jutta R; Keizer, Anouk; Engel, Manja M; Dijkerman, H Chris

2017-06-01

The sense of how we experience our physical body as our own represents a fundamental component of human self-awareness. Body ownership can be studied with bodily illusions which are generated by inducing a visuo-tactile conflict where individuals experience illusionary ownership over a fake body or body part, such as a rubber hand. Previous studies showed that different types of touch modulate the strength of experienced ownership over a rubber hand. Specifically, participants experienced more ownership after the rubber hand illusion was induced through affective touch vs non-affective touch. It is, however, unclear whether this effect would also occur for an entire fake body. The aim of this study was, therefore, to investigate whether affective touch modulates the strength of ownership in a virtual reality full body illusion. To elicit this illusion, we used slow (3 cm/s; affective touch) and fast (30 cm/s; non-affective touch) stroking velocities on the participants' abdomen. Both stroking velocities were performed either synchronous or asynchronous (control condition), while participants viewed a virtual body from a first-person-perspective. In our first study, we found that participants experienced more subjective ownership over a virtual body in the affective touch condition, compared to the non-affective touch condition. In our second study, we found higher levels of subjective ownership for synchronous stimulation, compared to asynchronous, for both touch conditions, but failed to replicate the findings from study 1 that show a difference between affective and non-affective touch. We, therefore, cannot conclude unequivocally that affective touch enhances the full-body illusion. Future research is required to study the effects of affective touch on body ownership.

Touching my left elbow: the anatomical structure of the body affects the illusion of self-touch.

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White, Rebekah C; Aimola Davies, Anne M

2011-01-01

A self-touch paradigm is used to create the illusion that one is touching one's own left elbow when one is actually touching the examiner's arm. Our new self-touch illusion is sensitive to the anatomical structure of the body: you can touch your left elbow with your right index finger but not with your left index finger. Illusion onset was faster and illusion ratings were higher when participants administered touch using the plausible right index finger compared with the implausible left index finger.

White noise speech illusion and psychosis expression: An experimental investigation of psychosis liability.

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Pries, Lotta-Katrin; Guloksuz, Sinan; Menne-Lothmann, Claudia; Decoster, Jeroen; van Winkel, Ruud; Collip, Dina; Delespaul, Philippe; De Hert, Marc; Derom, Catherine; Thiery, Evert; Jacobs, Nele; Wichers, Marieke; Simons, Claudia J P; Rutten, Bart P F; van Os, Jim

2017-01-01

An association between white noise speech illusion and psychotic symptoms has been reported in patients and their relatives. This supports the theory that bottom-up and top-down perceptual processes are involved in the mechanisms underlying perceptual abnormalities. However, findings in nonclinical populations have been conflicting. The aim of this study was to examine the association between white noise speech illusion and subclinical expression of psychotic symptoms in a nonclinical sample. Findings were compared to previous results to investigate potential methodology dependent differences. In a general population adolescent and young adult twin sample (n = 704), the association between white noise speech illusion and subclinical psychotic experiences, using the Structured Interview for Schizotypy-Revised (SIS-R) and the Community Assessment of Psychic Experiences (CAPE), was analyzed using multilevel logistic regression analyses. Perception of any white noise speech illusion was not associated with either positive or negative schizotypy in the general population twin sample, using the method by Galdos et al. (2011) (positive: ORadjusted: 0.82, 95% CI: 0.6-1.12, p = 0.217; negative: ORadjusted: 0.75, 95% CI: 0.56-1.02, p = 0.065) and the method by Catalan et al. (2014) (positive: ORadjusted: 1.11, 95% CI: 0.79-1.57, p = 0.557). No association was found between CAPE scores and speech illusion (ORadjusted: 1.25, 95% CI: 0.88-1.79, p = 0.220). For the Catalan et al. (2014) but not the Galdos et al. (2011) method, a negative association was apparent between positive schizotypy and speech illusion with positive or negative affective valence (ORadjusted: 0.44, 95% CI: 0.24-0.81, p = 0.008). Contrary to findings in clinical populations, white noise speech illusion may not be associated with psychosis proneness in nonclinical populations.

The Müller-Lyer Illusion in a computational model of biological object recognition.

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Astrid Zeman

Full Text Available Studying illusions provides insight into the way the brain processes information. The Müller-Lyer Illusion (MLI is a classical geometrical illusion of size, in which perceived line length is decreased by arrowheads and increased by arrowtails. Many theories have been put forward to explain the MLI, such as misapplied size constancy scaling, the statistics of image-source relationships and the filtering properties of signal processing in primary visual areas. Artificial models of the ventral visual processing stream allow us to isolate factors hypothesised to cause the illusion and test how these affect classification performance. We trained a feed-forward feature hierarchical model, HMAX, to perform a dual category line length judgment task (short versus long with over 90% accuracy. We then tested the system in its ability to judge relative line lengths for images in a control set versus images that induce the MLI in humans. Results from the computational model show an overall illusory effect similar to that experienced by human subjects. No natural images were used for training, implying that misapplied size constancy and image-source statistics are not necessary factors for generating the illusion. A post-hoc analysis of response weights within a representative trained network ruled out the possibility that the illusion is caused by a reliance on information at low spatial frequencies. Our results suggest that the MLI can be produced using only feed-forward, neurophysiological connections.

Perception of contextual size illusions by honeybees in restricted and unrestricted viewing conditions.

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Howard, Scarlett R; Avarguès-Weber, Aurore; Garcia, Jair E; Stuart-Fox, Devi; Dyer, Adrian G

2017-11-29

How different visual systems process images and make perceptual errors can inform us about cognitive and visual processes. One of the strongest geometric errors in perception is a misperception of size depending on the size of surrounding objects, known as the Ebbinghaus or Titchener illusion. The ability to perceive the Ebbinghaus illusion appears to vary dramatically among vertebrate species, and even populations, but this may depend on whether the viewing distance is restricted. We tested whether honeybees perceive contextual size illusions, and whether errors in perception of size differed under restricted and unrestricted viewing conditions. When the viewing distance was unrestricted, there was an effect of context on size perception and thus, similar to humans, honeybees perceived contrast size illusions. However, when the viewing distance was restricted, bees were able to judge absolute size accurately and did not succumb to visual illusions, despite differing contextual information. Our results show that accurate size perception depends on viewing conditions, and thus may explain the wide variation in previously reported findings across species. These results provide insight into the evolution of visual mechanisms across vertebrate and invertebrate taxa, and suggest convergent evolution of a visual processing solution. © 2017 The Author(s).

Illusion of control: the role of personal involvement.

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Yarritu, Ion; Matute, Helena; Vadillo, Miguel A

2014-01-01

The illusion of control consists of overestimating the influence that our behavior exerts over uncontrollable outcomes. Available evidence suggests that an important factor in development of this illusion is the personal involvement of participants who are trying to obtain the outcome. The dominant view assumes that this is due to social motivations and self-esteem protection. We propose that this may be due to a bias in contingency detection which occurs when the probability of the action (i.e., of the potential cause) is high. Indeed, personal involvement might have been often confounded with the probability of acting, as participants who are more involved tend to act more frequently than those for whom the outcome is irrelevant and therefore become mere observers. We tested these two variables separately. In two experiments, the outcome was always uncontrollable and we used a yoked design in which the participants of one condition were actively involved in obtaining it and the participants in the other condition observed the adventitious cause-effect pairs. The results support the latter approach: Those acting more often to obtain the outcome developed stronger illusions, and so did their yoked counterparts.

Illusion thermodynamics: A camouflage technique changing an object into another one with arbitrary cross section

International Nuclear Information System (INIS)

He, Xiao; Wu, Linzhi

2014-01-01

The previously reported magical thermal devices, such as the thermal invisible cloak and the thermal concentrator, are generalized into one general case named here thermal illusion device. The thermal illusion device is displayed by the design of a thermal reshaper which can reshape an arbitrary thermal object into another one with arbitrary cross section. General expressions of the material parameters for the thermal reshaper are derived unambiguously to greatly facilitate the design of general thermal illusion device. We believe that this work will broaden the current research and pave a path to the thermal invisibility. Numerical simulations show good agreement with the analytical results of the thermal illusion device

Illusion thermodynamics: A camouflage technique changing an object into another one with arbitrary cross section

Energy Technology Data Exchange (ETDEWEB)

He, Xiao; Wu, Linzhi, E-mail: wlz@hit.edu.cn [Center for Composite Materials, Harbin Institute of Technology, Harbin 150001 (China)

2014-12-01

The previously reported magical thermal devices, such as the thermal invisible cloak and the thermal concentrator, are generalized into one general case named here thermal illusion device. The thermal illusion device is displayed by the design of a thermal reshaper which can reshape an arbitrary thermal object into another one with arbitrary cross section. General expressions of the material parameters for the thermal reshaper are derived unambiguously to greatly facilitate the design of general thermal illusion device. We believe that this work will broaden the current research and pave a path to the thermal invisibility. Numerical simulations show good agreement with the analytical results of the thermal illusion device.

Enhancing performance expectancies through visual illusions facilitates motor learning in children.

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Bahmani, Moslem; Wulf, Gabriele; Ghadiri, Farhad; Karimi, Saeed; Lewthwaite, Rebecca

2017-10-01

In a recent study by Chauvel, Wulf, and Maquestiaux (2015), golf putting performance was found to be affected by the Ebbinghaus illusion. Specifically, adult participants demonstrated more effective learning when they practiced with a hole that was surrounded by small circles, making it look larger, than when the hole was surrounded by large circles, making it look smaller. The present study examined whether this learning advantage would generalize to children who are assumed to be less sensitive to the visual illusion. Two groups of 10-year olds practiced putting golf balls from a distance of 2m, with perceived larger or smaller holes resulting from the visual illusion. Self-efficacy was increased in the group with the perceived larger hole. The latter group also demonstrated more accurate putting performance during practice. Importantly, learning (i.e., delayed retention performance without the illusion) was enhanced in the group that practiced with the perceived larger hole. The findings replicate previous results with adult learners and are in line with the notion that enhanced performance expectancies are key to optimal motor learning (Wulf & Lewthwaite, 2016). Copyright © 2017 Elsevier B.V. All rights reserved.

Light Refraction by Water as a Rationale for the Poggendorff Illusion.

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Bozhevolnyi, Sergey I

2016-08-24

The Poggendorff illusion in its classical form of parallel lines interrupting a transversal is viewed from the perspective of being related to the everyday experience of observing the light refraction in water. It is argued that if one considers a transversal to be a light ray in air and the parallel lines to form an occluding strip of a medium with the refractive index being between that of air and water, then one should be able to account, both qualitatively and quantitatively, for most of the features associated with the Poggendorff illusion. Statistical treatment of the visual experiments conducted with seven participants, each analyzing 50 configurations having different intercepting angles and strip widths, resulted in the effective refractive index of the occluding strip N = 1.13 ± 0.15, which is sufficiently close to the average (between that of water and air) refractive index of ∼1.17. It is further argued that the same mechanism can also be employed to account for many variants of the Poggendorff illusion, including the corner-Poggendorff pattern, as well as for the Hering illusion. © The Author(s) 2016.

Robust brightness enhancement across a luminance range of the glare illusion.

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Tamura, Hideki; Nakauchi, Shigeki; Koida, Kowa

2016-01-01

The glare illusion refers to brightness enhancement and the perception of a self-luminous appearance that occurs when a central region is surrounded by a luminance gradient. The center region appears to be a light source, with its light dispersing into the surrounding region. If the luminous edge is critical for generating the illusion, modulating the perceived luminance of the image, and switching its appearance from luminous to nonluminous, would have a strong impact on lightness and brightness estimation. Here, we quantified the illusion in two ways, by assessing brightness enhancement and examining whether the center region appeared luminous. Thus, we could determine whether the two effects occurred jointly or independently. We examined a wide luminance range of center regions, from 0 to 200% relative to background. Brightness enhancement in the illusion was observed for a wide range of luminances (20% to 200% relative to background), while a luminous-white appearance was observed when the center region luminance was 145% of the background. These results exclude the possibility that brightness enhancement occurs because the stimuli appear self-luminous. We suggest that restoring the original image intensity precedes the perceptual process of lightness estimation.

Individual differences in the rubber-hand illusion: predicting self-reports of people's personal experiences.

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Haans, Antal; Kaiser, Florian G; Bouwhuis, Don G; Ijsselsteijn, Wijnand A

2012-10-01

Can we assess individual differences in the extent to which a person perceives the rubber-hand illusion on the basis of self-reported experiences? In this research, we develop such an instrument using Rasch-type models. In our conception, incorporating an object (e.g., a rubber hand) into one's body image requires various sensorimotor and cognitive processes. The extent to which people can meet these requirements thus determines how intensely people experience and, simultaneously, describe the illusion. As a consequence, individual differences in people's susceptibility to the rubber-hand illusion can be determined by inspecting reports of their personal experiences. The proposed model turned out to be functional in its capability to predict self-reports of people's experiences and to reliably assess individual differences in susceptibility to the illusion. Regarding validity, we found a small, but significant, correlation between individual susceptibility and proprioceptive drift. Additionally, we found that asynchrony, and tapping rather than stroking the fingers constrain the experience of the illusion. Copyright © 2012 Elsevier B.V. All rights reserved.

Electromagnetic illusion with isotropic and homogeneous materials through scattering manipulation

International Nuclear Information System (INIS)

Yang, Fan; Mei, Zhong Lei; Jiang, Wei Xiang; Cui, Tie Jun

2015-01-01

A new isotropic and homogeneous illusion device for electromagnetic waves is proposed. This single-shelled device can change the fingerprint of the covered object into another one by manipulating the scattering of the composite structure. We show that an electrically small sphere can be disguised as another small one with different electromagnetic parameters. The device can even make a dielectric sphere (electrically small) behave like a conducting one. Full-wave simulations confirm the performance of proposed illusion device. (paper)

Tuning and disrupting the brain – modulating the McGurk illusion with electrical stimulation

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Lucas M Marques

2014-08-01

Full Text Available In the so-called McGurk illusion, when the synchronized presentation of the visual stimulus /ga/ is paired with the auditory stimulus /ba/, people in general hear it as /da/. Multisensory integration processing underlying this illusion seems to occur within the Superior Temporal Sulcus (STS. Herein, we present evidence demonstrating that bilateral cathodal transcranial direct current stimulation (tDCS of this area can decrease the McGurk illusion-type responses. Additionally, we show that the manipulation of this audio-visual integrated output occurs irrespective of the number of eye-fixations on the mouth of the speaker. Bilateral anodal tDCS of the Parietal Cortex also modulates the illusion, but in the opposite manner, inducing more illusion-type responses. This is the first demonstration of using non-invasive brain stimulation to modulate multisensory speech perception in an illusory context (i.e., both increasing and decreasing illusion-type responses to a verbal audio-visual integration task. These findings provide clear evidence that both the superior temporal and parietal areas contribute to multisensory integration processing related to speech perception. Specifically, STS seems fundamental for the temporal synchronization and integration of auditory and visual inputs. For its part, PPC may adjust the arrival of incoming audio and visual information to STS thereby enhancing their interaction in this latter area.

Dissociation of color and figure-ground effects in the watercolor illusion.

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Von der Heydt, Rüdiger; Pierson, Rachel

2006-01-01

Two phenomena can be observed in the watercolor illusion: illusory color spreading and figure-ground organization. We performed experiments to determine whether the figure-ground effect is a consequence of the color illusion or due to an independent mechanism. Subjects were tested with displays consisting of six adjacent compartments--three that generated the illusion alternating with three that served for comparison. In a first set of experiments, the illusory color was measured by finding the matching physical color in the alternate compartments. Figureness (probability of 'figure' responses, 2AFC) of the watercolor compartments was then determined with and without the matching color in the alternate compartments. The color match reduced figureness, but did not abolish it. There was a range of colors in which the watercolor compartments dominated as figures over the alternate compartments although the latter appeared more saturated in color. In another experiment, the effect of tinting alternate compartments was measured in displays without watercolor illusion. Figureness increased with color contrast, but its value at the equivalent contrast fell short of the figureness value obtained for the watercolor pattern. Thus, in both experiments, figureness produced by the watercolor pattern was stronger than expected from the color effect, suggesting independent mechanisms. Considering the neurophysiology, we propose that the color illusion follows from the principles of representation of surface color in the visual cortex, while the figure-ground effect results from two mechanisms of border ownership assignment, one that is sensitive to asymmetric shape of edge profile, the other to consistency of color borders.

Asymmetric effects of luminance and chrominance in the watercolor illusion

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Andrew eCoia

2014-09-01

Full Text Available When bounded by a line of sufficient contrast, the desaturated hue of a colored line will spread over an enclosed area, an effect known as the watercolor illusion. The contrast of the two lines can be in luminance, chromaticity, or a combination of both. The effect is most salient when the enclosing line has greater contrast with the background than the line that induces the spreading color. In most prior experiments with watercolor spreading, the luminance of both lines has been lower than the background. An achromatic version of the illusion exists where a dark line will spread while being bounded by either a darker or brighter line. In a previous study we measured the strength of the watercolor effect in which the colored inducing line was isoluminant to the background, and found an illusion for both brighter and darker achromatic outer contours. We also found the strength of spreading is stronger for bluish (+S cone input colors compared to yellowish (-S cone input ones, when bounded by a dark line. The current study set out to measure the hue dependence of the watercolor illusion when inducing colors are flanked with brighter (increment as opposed to darker outer lines. The asymmetry in the watercolor effect with S cone input was enhanced when the inducing contrast was an increment rather than a decrement. Further experiments explored the relationship between the perceived contrast of these chromatic lines when paired with luminance increments and decrements and revealed that the perceived contrast of luminance increments and decrements is dependent on which isoluminant color they are paired with. In addition to known hue asymmetries in the watercolor illusion there are asymmetries between luminance increments and decrements that are also hue dependent. These latter asymmetries may be related to the perceived contrast of the hue/luminance parings.

Asymmetric effects of luminance and chrominance in the watercolor illusion.

Science.gov (United States)

Coia, Andrew J; Crognale, Michael A

2014-01-01

When bounded by a line of sufficient contrast, the desaturated hue of a colored line will spread over an enclosed area, an effect known as the watercolor illusion. The contrast of the two lines can be in luminance, chromaticity, or a combination of both. The effect is most salient when the enclosing line has greater contrast with the background than the line that induces the spreading color. In most prior experiments with watercolor spreading, the luminance of both lines has been lower than the background. An achromatic version of the illusion exists where a dark line will spread while being bounded by either a darker or brighter line. In a previous study we measured the strength of the watercolor effect in which the colored inducing line was isoluminant to the background, and found an illusion for both brighter and darker achromatic outer contours. We also found the strength of spreading is stronger for bluish (+S cone input) colors compared to yellowish (-S cone input) ones, when bounded by a dark line. The current study set out to measure the hue dependence of the watercolor illusion when inducing colors are flanked with brighter (increment) as opposed to darker outer lines. The asymmetry in the watercolor effect with S cone input was enhanced when the inducing contrast was an increment rather than a decrement. Further experiments explored the relationship between the perceived contrast of these chromatic lines when paired with luminance increments and decrements and revealed that the perceived contrast of luminance increments and decrements is dependent on which isoluminant color they are paired with. In addition to known hue asymmetries in the watercolor illusion there are asymmetries between luminance increments and decrements that are also hue dependent. These latter asymmetries may be related to the perceived contrast of the hue/luminance parings.

Mysterious quantum Cheshire cat: an illusion

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Michielsen, K.; Lippert, Th.; De Raedt, H.

2015-09-01

We provide a mystery-free explanation for the experimentally observed facts in the neutron interferometry quantum Cheshire cat experiment of Denkmayr et al. [Nat. Comm. 5, 4492, 2014] in terms of a discrete-event simulation model, demonstrating that the quantum Cheshire cat is an illusion.

Negative cognitive errors and positive illusions for negative divorce events: predictors of children's psychological adjustment.

Science.gov (United States)

Mazur, E; Wolchik, S A; Sandler, I N

1992-12-01

This study examined the relations among negative cognitive errors regarding hypothetical negative divorce events, positive illusions about those same events, actual divorce events, and psychological adjustment in 38 8- to 12-year-old children whose parents had divorced within the previous 2 years. Children's scores on a scale of negative cognitive errors (catastrophizing, overgeneralizing, and personalizing) correlated significantly with self-reported symptoms of anxiety and self-esteem, and with maternal reports of behavior problems. Children's scores on a scale measuring positive illusions (high self-regard, illusion of personal control, and optimism for the future) correlated significantly with less self-reported aggression. Both appraisal types accounted for variance in some measures of symptomatology beyond that explained by actual events. There was no significant association between children's negative cognitive errors and positive illusions. The implications of these results for theories of negative cognitive errors and of positive illusions, as well as for future research, are discussed.

Why do animals differ in their susceptibility to geometrical illusions?

Science.gov (United States)

Feng, Lynna C; Chouinard, Philippe A; Howell, Tiffani J; Bennett, Pauleen C

2017-04-01

In humans, geometrical illusions are thought to reflect mechanisms that are usually helpful for seeing the world in a predictable manner. These mechanisms deceive us given the right set of circumstances, correcting visual input where a correction is not necessary. Investigations of non-human animals' susceptibility to geometrical illusions have yielded contradictory results, suggesting that the underlying mechanisms with which animals see the world may differ across species. In this review, we first collate studies showing that different species are susceptible to specific illusions in the same or reverse direction as humans. Based on a careful assessment of these findings, we then propose several ecological and anatomical factors that may affect how a species perceives illusory stimuli. We also consider the usefulness of this information for determining whether sight in different species might be more similar to human sight, being influenced by contextual information, or to how machines process and transmit information as programmed. Future testing in animals could provide new theoretical insights by focusing on establishing dissociations between stimuli that may or may not alter perception in a particular species. This information could improve our understanding of the mechanisms behind illusions, but also provide insight into how sight is subjectively experienced by different animals, and the degree to which vision is innate versus acquired, which is difficult to examine in humans.

Effects of age and brightness contrast on perception of the Wundt-Hering illusion.

Science.gov (United States)

Astor-Stetson, E; Purnell, T G

1990-10-01

Susceptibility to the Wundt-Hering illusion was studied as a function of age and contrast. Preschoolers, third-graders and college students were shown light-grey, medium-grey, and black Wundt-Hering figures on white ground. Pre-schoolers were most susceptible to the illusion, differing from third graders in the medium and high contrast conditions and from college students in all contrast conditions. Low contrast figures resulted in significantly less distortion than did high contrast figures for the preschoolers. The significant interaction of age and contrast effects highlights the importance of a developmental approach to the study of illusions.

Visual illusions on the Internet: 15 years of change in technology and user behavior.

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Bach, Michael

2014-01-01

Abstract. Looking back over 15 years of demonstrating visual phenomena and optical illusions on the Internet, I will discuss two major topics. The first concerns the methodology used to present interactive visual experiments on the web, with respect to (a) wide accessibility, ie independent of browser and platform, (b) capable and elegant graphic user interface, (c) sufficient computational power, (d) ease of development and, finally, (e) future-proofing in an ever-changing online environment. The second major topic addresses some aspects of user behaviour, mainly temporal patterns (eg changes over weeks. years, long-term), which reveal that there are more visitors during office hours.

Assessment of Positive Illusions of the Physical Attractiveness of Romantic Partners

OpenAIRE

Barelds, D.P.H.; Dijkstra, Pieternel; Koudenburg, N.; Swami, V.

2011-01-01

Positive illusions about a partner's physical attractiveness occur when individuals' ratings of their partner's attractiveness are more positive than more objective ratings. Ratings that may serve as a''reality benchmark' include ratings by the partner him/herself and observer ratings. The present study compared the effects of using different reality benchmarks on the strength of positive partner physical attractiveness illusions (n = 70 couples). Results showed that individuals positively bi...

A Virtual Reality Full Body Illusion Improves Body Image Disturbance in Anorexia Nervosa

NARCIS (Netherlands)

Keizer, Anouk; van Elburg, Annemarie; Helms, Rossa; Dijkerman, H Chris

2016-01-01

BACKGROUND: Patients with anorexia nervosa (AN) have a persistent distorted experience of the size of their body. Previously we found that the Rubber Hand Illusion improves hand size estimation in this group. Here we investigated whether a Full Body Illusion (FBI) affects body size estimation of

Humanlike robot hands controlled by brain activity arouse illusion of ownership in operators

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Alimardani, Maryam; Nishio, Shuichi; Ishiguro, Hiroshi

2013-08-01

Operators of a pair of robotic hands report ownership for those hands when they hold image of a grasp motion and watch the robot perform it. We present a novel body ownership illusion that is induced by merely watching and controlling robot's motions through a brain machine interface. In past studies, body ownership illusions were induced by correlation of such sensory inputs as vision, touch and proprioception. However, in the presented illusion none of the mentioned sensations are integrated except vision. Our results show that during BMI-operation of robotic hands, the interaction between motor commands and visual feedback of the intended motions is adequate to incorporate the non-body limbs into one's own body. Our discussion focuses on the role of proprioceptive information in the mechanism of agency-driven illusions. We believe that our findings will contribute to improvement of tele-presence systems in which operators incorporate BMI-operated robots into their body representations.

Weber's Illusion and Body Shape: Anisotropy of Tactile Size Perception on the Hand

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Longo, Matthew R.; Haggard, Patrick

2011-01-01

The perceived distance between touches on a single skin surface is larger on regions of high tactile sensitivity than those with lower acuity, an effect known as "Weber's illusion". This illusion suggests that tactile size perception involves a representation of the perceived size of body parts preserving characteristics of the somatosensory…

Tunable Graphene Metasurface Reflectarray for Cloaking, Illusion, and Focusing

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Biswas, Sudipta Romen; Gutiérrez, Cristian E.; Nemilentsau, Andrei; Lee, In-Ho; Oh, Sang-Hyun; Avouris, Phaedon; Low, Tony

2018-03-01

This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. We present a graphene-based metasurface that can be actively tuned between different regimes of operation, such as anomalous beam steering and focusing, cloaking, and illusion optics, by applying electrostatic gating without modifying the geometry of the metasurface. The metasurface is designed by placing graphene ribbons on a dielectric cavity resonator, where interplay between geometric plasmon resonances in the ribbons and Fabry-Perot resonances in the cavity is used to achieve a 2 π phase shift. As a proof of concept, we demonstrate that the wave front of the field reflected from a triangular bump covered by the metasurface can be tuned by applying electric bias so as to resemble that of a bare plane and of a spherical object. Moreover, reflective focusing and the change of the reflection direction for the above mentioned cases are also shown.

Explaining away the body: experiences of supernaturally caused touch and touch on non-hand objects within the rubber hand illusion.

Directory of Open Access Journals (Sweden)

Jakob Hohwy

2010-02-01

Full Text Available In rubber hand illusions and full body illusions, touch sensations are projected to non-body objects such as rubber hands, dolls or virtual bodies. The robustness, limits and further perceptual consequences of such illusions are not yet fully explored or understood. A number of experiments are reported that test the limits of a variant of the rubber hand illusion.A variant of the rubber hand illusion is explored, in which the real and foreign hands are aligned in personal space. The presence of the illusion is ascertained with participants' scores and temperature changes of the real arm. This generates a basic illusion of touch projected to a foreign arm. Participants are presented with further, unusual visuotactile stimuli subsequent to onset of the basic illusion. Such further visuotactile stimulation is found to generate very unusual experiences of supernatural touch and touch on a non-hand object. The finding of touch on a non-hand object conflicts with prior findings, and to resolve this conflict a further hypothesis is successfully tested: that without prior onset of the basic illusion this unusual experience does not occur.A rubber hand illusion is found that can arise when the real and the foreign arm are aligned in personal space. This illusion persists through periods of no tactile stimulation and is strong enough to allow very unusual experiences of touch felt on a cardboard box and experiences of touch produced at a distance, as if by supernatural causation. These findings suggest that one's visual body image is explained away during experience of the illusion and they may be of further importance to understanding the role of experience in delusion formation. The findings of touch on non-hand objects may help reconcile conflicting results in this area of research. In addition, new evidence is provided that relates to the recently discovered psychologically induced temperature changes that occur during the illusion.

The working memory Ponzo illusion: Involuntary integration of visuospatial information stored in visual working memory.

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Shen, Mowei; Xu, Haokui; Zhang, Haihang; Shui, Rende; Zhang, Meng; Zhou, Jifan

2015-08-01

Visual working memory (VWM) has been traditionally viewed as a mental structure subsequent to visual perception that stores the final output of perceptual processing. However, VWM has recently been emphasized as a critical component of online perception, providing storage for the intermediate perceptual representations produced during visual processing. This interactive view holds the core assumption that VWM is not the terminus of perceptual processing; the stored visual information rather continues to undergo perceptual processing if necessary. The current study tests this assumption, demonstrating an example of involuntary integration of the VWM content, by creating the Ponzo illusion in VWM: when the Ponzo illusion figure was divided into its individual components and sequentially encoded into VWM, the temporally separated components were involuntarily integrated, leading to the distorted length perception of the two horizontal lines. This VWM Ponzo illusion was replicated when the figure components were presented in different combinations and presentation order. The magnitude of the illusion was significantly correlated between VWM and perceptual versions of the Ponzo illusion. These results suggest that the information integration underling the VWM Ponzo illusion is constrained by the laws of visual perception and similarly affected by the common individual factors that govern its perception. Thus, our findings provide compelling evidence that VWM functions as a buffer serving perceptual processes at early stages. Copyright © 2015 Elsevier B.V. All rights reserved.

How virtual reality works: illusions of vision in "real" and virtual environments

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Stark, Lawrence W.

1995-04-01

Visual illusions abound in normal vision--illusions of clarity and completeness, of continuity in time and space, of presence and vivacity--and are part and parcel of the visual world inwhich we live. These illusions are discussed in terms of the human visual system, with its high- resolution fovea, moved from point to point in the visual scene by rapid saccadic eye movements (EMs). This sampling of visual information is supplemented by a low-resolution, wide peripheral field of view, especially sensitive to motion. Cognitive-spatial models controlling perception, imagery, and 'seeing,' also control the EMs that shift the fovea in the Scanpath mode. These illusions provide for presence, the sense off being within an environment. They equally well lead to 'Telepresence,' the sense of being within a virtual display, especially if the operator is intensely interacting within an eye-hand and head-eye human-machine interface that provides for congruent visual and motor frames of reference. Interaction, immersion, and interest compel telepresence; intuitive functioning and engineered information flows can optimize human adaptation to the artificial new world of virtual reality, as virtual reality expands into entertainment, simulation, telerobotics, and scientific visualization and other professional work.

The Mirrored Hand Illusion: I Control, So I Possess?

Science.gov (United States)

Zhou, Aibao; Zhang, Yanchi; Yin, Yulong; Yang, Yang

2015-01-01

Certain situations may not only cause people to misjudge external information but also distort people's perception of themselves. The present study is the first to report the mirrored hand illusion which could be generated when the experimenter imitated the fist-clenching movements of the subject synchronously. The subjects formed the illusion that the experimenter's hand was "something I can control" when being imitated synchronously. In addition, a sense of ownership over the alien hand was established by integrating multisensory signals and comparing these signals with preexisting body presentations. This method might represent a new avenue for research on the formation of self-consciousness. © The Author(s) 2015.

Development of the False-Memory Illusion

Science.gov (United States)

Brainerd, C. J.; Forrest, T. J.; Karibian, D.; Reyna, V. F.

2006-01-01

The counterintuitive developmental trend in the Deese-Roediger-McDermott (DRM) illusion (that false-memory responses increase with age) was investigated in learning-disabled and nondisabled children from the 6- to 14-year-old age range. Fuzzy-trace theory predicts that because there are qualitative differences in how younger versus older children…

Rubens Peale's spectacles: an optical illusion?

Science.gov (United States)

Follensbee, B J

1997-01-01

The painting Rubens Peale with a Geranium (1801), by Rembrandt Peale, has earned a reputation as a masterpiece of early American portraiture. In recent years the painting has also been the source of controversy, because Rubens was depicted with two pairs of eyeglasses at a time when most people would not have been portrayed with spectacles at all. Scholars of American art history and ophthalmology have studied the painting and have promoted various theories for this peculiarity. A combined study of the painting, historical documentation, and optical effects in the painting, however, sheds new light on the answer to this mystery.

A mass-density model can account for the size-weight illusion

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Bergmann Tiest, Wouter M.; Drewing, Knut

2018-01-01

When judging the heaviness of two objects with equal mass, people perceive the smaller and denser of the two as being heavier. Despite the large number of theories, covering bottom-up and top-down approaches, none of them can fully account for all aspects of this size-weight illusion and thus for human heaviness perception. Here we propose a new maximum-likelihood estimation model which describes the illusion as the weighted average of two heaviness estimates with correlated noise: One estimate derived from the object’s mass, and the other from the object’s density, with estimates’ weights based on their relative reliabilities. While information about mass can directly be perceived, information about density will in some cases first have to be derived from mass and volume. However, according to our model at the crucial perceptual level, heaviness judgments will be biased by the objects’ density, not by its size. In two magnitude estimation experiments, we tested model predictions for the visual and the haptic size-weight illusion. Participants lifted objects which varied in mass and density. We additionally varied the reliability of the density estimate by varying the quality of either visual (Experiment 1) or haptic (Experiment 2) volume information. As predicted, with increasing quality of volume information, heaviness judgments were increasingly biased towards the object’s density: Objects of the same density were perceived as more similar and big objects were perceived as increasingly lighter than small (denser) objects of the same mass. This perceived difference increased with an increasing difference in density. In an additional two-alternative forced choice heaviness experiment, we replicated that the illusion strength increased with the quality of volume information (Experiment 3). Overall, the results highly corroborate our model, which seems promising as a starting point for a unifying framework for the size-weight illusion and human heaviness

A mass-density model can account for the size-weight illusion.

Science.gov (United States)

Wolf, Christian; Bergmann Tiest, Wouter M; Drewing, Knut

2018-01-01

When judging the heaviness of two objects with equal mass, people perceive the smaller and denser of the two as being heavier. Despite the large number of theories, covering bottom-up and top-down approaches, none of them can fully account for all aspects of this size-weight illusion and thus for human heaviness perception. Here we propose a new maximum-likelihood estimation model which describes the illusion as the weighted average of two heaviness estimates with correlated noise: One estimate derived from the object's mass, and the other from the object's density, with estimates' weights based on their relative reliabilities. While information about mass can directly be perceived, information about density will in some cases first have to be derived from mass and volume. However, according to our model at the crucial perceptual level, heaviness judgments will be biased by the objects' density, not by its size. In two magnitude estimation experiments, we tested model predictions for the visual and the haptic size-weight illusion. Participants lifted objects which varied in mass and density. We additionally varied the reliability of the density estimate by varying the quality of either visual (Experiment 1) or haptic (Experiment 2) volume information. As predicted, with increasing quality of volume information, heaviness judgments were increasingly biased towards the object's density: Objects of the same density were perceived as more similar and big objects were perceived as increasingly lighter than small (denser) objects of the same mass. This perceived difference increased with an increasing difference in density. In an additional two-alternative forced choice heaviness experiment, we replicated that the illusion strength increased with the quality of volume information (Experiment 3). Overall, the results highly corroborate our model, which seems promising as a starting point for a unifying framework for the size-weight illusion and human heaviness perception.

Active inference, sensory attenuation and illusions.

Science.gov (United States)

Brown, Harriet; Adams, Rick A; Parees, Isabel; Edwards, Mark; Friston, Karl

2013-11-01

Active inference provides a simple and neurobiologically plausible account of how action and perception are coupled in producing (Bayes) optimal behaviour. This can be seen most easily as minimising prediction error: we can either change our predictions to explain sensory input through perception. Alternatively, we can actively change sensory input to fulfil our predictions. In active inference, this action is mediated by classical reflex arcs that minimise proprioceptive prediction error created by descending proprioceptive predictions. However, this creates a conflict between action and perception; in that, self-generated movements require predictions to override the sensory evidence that one is not actually moving. However, ignoring sensory evidence means that externally generated sensations will not be perceived. Conversely, attending to (proprioceptive and somatosensory) sensations enables the detection of externally generated events but precludes generation of actions. This conflict can be resolved by attenuating the precision of sensory evidence during movement or, equivalently, attending away from the consequences of self-made acts. We propose that this Bayes optimal withdrawal of precise sensory evidence during movement is the cause of psychophysical sensory attenuation. Furthermore, it explains the force-matching illusion and reproduces empirical results almost exactly. Finally, if attenuation is removed, the force-matching illusion disappears and false (delusional) inferences about agency emerge. This is important, given the negative correlation between sensory attenuation and delusional beliefs in normal subjects--and the reduction in the magnitude of the illusion in schizophrenia. Active inference therefore links the neuromodulatory optimisation of precision to sensory attenuation and illusory phenomena during the attribution of agency in normal subjects. It also provides a functional account of deficits in syndromes characterised by false inference

The Bicycle Illusion: Sidewalk Science Informs the Integration of Motion and Shape Perception

Science.gov (United States)

Masson, Michael E. J.; Dodd, Michael D.; Enns, James T.

2009-01-01

The authors describe a new visual illusion first discovered in a natural setting. A cyclist riding beside a pair of sagging chains that connect fence posts appears to move up and down with the chains. In this illusion, a static shape (the chains) affects the perception of a moving shape (the bicycle), and this influence involves assimilation…

Scattering engineering in continuously shaped metasurface: An approach for electromagnetic illusion

Science.gov (United States)

Guo, Yinghui; Yan, Lianshan; Pan, Wei; Shao, Liyang

2016-07-01

The control of electromagnetic waves scattering is critical in wireless communications and stealth technology. Discrete metasurfaces not only increase the design and fabrication complex but also cause difficulties in obtaining simultaneous electric and optical functionality. On the other hand, discontinuous phase profiles fostered by discrete systems inevitably introduce phase noises to the scattering fields. Here we propose the principle of a scattering-harness mechanism by utilizing continuous gradient phase stemming from the spin-orbit interaction via sinusoidal metallic strips. Furthermore, by adjusting the amplitude and period of the sinusoidal metallic strip, the scattering characteristics of the underneath object can be greatly changed and thus result in electromagnetic illusion. The proposal is validated by full-wave simulations and experiment characterization in microwave band. Our approach featured by continuous phase profile, polarization independent performance and facile implementation may find widespread applications in electromagnetic wave manipulation.

The Illusion of Owning a Third Arm

Science.gov (United States)

Ehrsson, H. Henrik

2011-01-01

Could it be possible that, in the not-so-distant future, we will be able to reshape the human body so as to have extra limbs? A third arm helping us out with the weekly shopping in the local grocery store, or an extra artificial limb assisting a paralysed person? Here we report a perceptual illusion in which a rubber right hand, placed beside the real hand in full view of the participant, is perceived as a supernumerary limb belonging to the participant's own body. This effect was supported by questionnaire data in conjunction with physiological evidence obtained from skin conductance responses when physically threatening either the rubber hand or the real one. In four well-controlled experiments, we demonstrate the minimal required conditions for the elicitation of this “supernumerary hand illusion”. In the fifth, and final experiment, we show that the illusion reported here is qualitatively different from the traditional rubber hand illusion as it is characterised by less disownership of the real hand and a stronger feeling of having two right hands. These results suggest that the artificial hand ‘borrows’ some of the multisensory processes that represent the real hand, leading to duplication of touch and ownership of two right arms. This work represents a major advance because it challenges the traditional view of the gross morphology of the human body as a fundamental constraint on what we can come to experience as our physical self, by showing that the body representation can easily be updated to incorporate an additional limb. PMID:21383847

Illusions and delusions: relating experimentally-induced false memories to anomalous experiences and ideas

Directory of Open Access Journals (Sweden)

Philip R Corlett

2009-11-01

Full Text Available The salience hypothesis of psychosis rests on a simple but profound observation that subtle alterations in the way that we perceive and experience stimuli have important consequences for how important these stimuli become for us, how much they draw our attention, how they embed themselves in our memory and, ultimately, how they shape our beliefs. We put forward the idea that a classical memory illusion – the Deese-Roediger-McDermott (DRM effect – offers a useful way of exploring processes related to such aberrant belief formation. The illusion occurs when, as a consequence of its relationship to previous stimuli, a stimulus is asserted to be remembered even when has not been previously presented. Such illusory familiarity is thought to be generated by the surprising fluency with which the stimulus is processed. In this respect, the illusion relates directly to the salience hypothesis and may share common cognitive underpinnings with aberrations of perception and attribution that are found in psychosis. In this paper, we explore the theoretical importance of this experimentally-induced illusion in relation to the salience model of psychosis. We present data showing that, in healthy volunteers, the illusion relates directly to self reported anomalies of experience and magical thinking. We discuss this finding in terms of the salience hypothesis and of a broader Bayesian framework of perception and cognition which emphasizes the salience both of predictable and unpredictable experiences..

Susceptibility to Optical Illusions Varies as a Function of the Autism-Spectrum Quotient but Not in Ways Predicted by Local-Global Biases

Science.gov (United States)

Chouinard, Philippe A.; Unwin, Katy L.; Landry, Oriane; Sperandio, Irene

2016-01-01

Individuals with autism spectrum disorder and those with autistic tendencies in non-clinical groups are thought to have a perceptual style privileging local details over global integration. We used 13 illusions to investigate this perceptual style in typically developing adults with various levels of autistic traits. Illusory susceptibility was…

Neural correlates of visually induced self-motion illusion in depth.

Science.gov (United States)

Kovács, Gyula; Raabe, Markus; Greenlee, Mark W

2008-08-01

Optic-flow fields can induce the conscious illusion of self-motion in a stationary observer. Here we used functional magnetic resonance imaging to reveal the differential processing of self- and object-motion in the human brain. Subjects were presented a constantly expanding optic-flow stimulus, composed of disparate red-blue dots, viewed through red-blue glasses to generate a vivid percept of three-dimensional motion. We compared the activity obtained during periods of illusory self-motion with periods of object-motion percept. We found that the right MT+, precuneus, as well as areas located bilaterally along the dorsal part of the intraparietal sulcus and along the left posterior intraparietal sulcus were more active during self-motion perception than during object-motion. Additional signal increases were located in the depth of the left superior frontal sulcus, over the ventral part of the left anterior cingulate, in the depth of the right central sulcus and in the caudate nucleus/putamen. We found no significant deactivations associated with self-motion perception. Our results suggest that the illusory percept of self-motion is correlated with the activation of a network of areas, ranging from motion-specific areas to regions involved in visuo-vestibular integration, visual imagery, decision making, and introspection.

Memory illusion in high-functioning autism and Asperger's disorder.

Science.gov (United States)

Kamio, Yoko; Toichi, Motomi

2007-05-01

In this study, 13 individuals with high-functioning autism (HFA), 15 individuals with Asperger's disorder (AD), and age-, and IQ-matched controls were presented a list of sentences auditorily. Participants then evaluated semantically related but new sentences and reported whether they were old or new. The total rates of false recognition for semantically related sentences were similar among the three groups. Nevertheless, memory illusion on some aspects was reduced in HFA participants. These results suggest that HFA have difficulties in semantic association. Although individuals with AD showed no quantitative abnormalities of memory illusion, some contributing factors were atypical. These findings are discussed in terms of schema theory, enhanced perceptual processing hypothesis, and weak central coherence hypothesis.

Positive illusions about one's partner's physical attractiveness

NARCIS (Netherlands)

Barelds-Dijkstra, Pieternel; Barelds, Dick P. H.

This study examined couples' ratings of self and partner physical attractiveness. On the basis of the theory of positive illusions, it was expected that individuals would rate their partners as more attractive than their partners would rate themselves. Both members of 93 heterosexual couples, with a

Can walking motions improve visually induced rotational self-motion illusions in virtual reality?

Science.gov (United States)

Riecke, Bernhard E; Freiberg, Jacob B; Grechkin, Timofey Y

2015-02-04

Illusions of self-motion (vection) can provide compelling sensations of moving through virtual environments without the need for complex motion simulators or large tracked physical walking spaces. Here we explore the interaction between biomechanical cues (stepping along a rotating circular treadmill) and visual cues (viewing simulated self-rotation) for providing stationary users a compelling sensation of rotational self-motion (circular vection). When tested individually, biomechanical and visual cues were similarly effective in eliciting self-motion illusions. However, in combination they yielded significantly more intense self-motion illusions. These findings provide the first compelling evidence that walking motions can be used to significantly enhance visually induced rotational self-motion perception in virtual environments (and vice versa) without having to provide for physical self-motion or motion platforms. This is noteworthy, as linear treadmills have been found to actually impair visually induced translational self-motion perception (Ash, Palmisano, Apthorp, & Allison, 2013). Given the predominant focus on linear walking interfaces for virtual-reality locomotion, our findings suggest that investigating circular and curvilinear walking interfaces offers a promising direction for future research and development and can help to enhance self-motion illusions, presence and immersion in virtual-reality systems. © 2015 ARVO.

Category Selectivity of Human Visual Cortex in Perception of Rubin Face–Vase Illusion

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Xiaogang Wang

2017-09-01

Full Text Available When viewing the Rubin face–vase illusion, our conscious perception spontaneously alternates between the face and the vase; this illusion has been widely used to explore bistable perception. Previous functional magnetic resonance imaging (fMRI studies have studied the neural mechanisms underlying bistable perception through univariate and multivariate pattern analyses; however, no studies have investigated the issue of category selectivity. Here, we used fMRI to investigate the neural mechanisms underlying the Rubin face–vase illusion by introducing univariate amplitude and multivariate pattern analyses. The results from the amplitude analysis suggested that the activity in the fusiform face area was likely related to the subjective face perception. Furthermore, the pattern analysis results showed that the early visual cortex (EVC and the face-selective cortex could discriminate the activity patterns of the face and vase perceptions. However, further analysis of the activity patterns showed that only the face-selective cortex contains the face information. These findings indicated that although the EVC and face-selective cortex activities could discriminate the visual information, only the activity and activity pattern in the face-selective areas contained the category information of face perception in the Rubin face–vase illusion.

Towards a digital body: the virtual arm illusion

Directory of Open Access Journals (Sweden)

2008-08-01

Full Text Available The integration of the human brain with computers is an interesting new area of applied neuroscience, where one application is replacement of a person’s real body by a virtual representation. Here we demonstrate that a virtual limb can be made to feel part of your body if appropriate multisensory correlations are provided. We report an illusion that is invoked through tactile stimulation on a person’s hidden real right hand with synchronous virtual visual stimulation on an aligned 3D stereo virtual arm projecting horizontally out of their shoulder. An experiment with 21 male participants showed displacement of ownership towards the virtual hand, as illustrated by questionnaire responses and proprioceptive drift. A control experiment with asynchronous tapping was carried out with a different set of 20 male participants who did not experience the illusion. After 5 minutes of stimulation the virtual arm rotated. Evidence suggests that the extent of the illusion was also correlated with the degree of muscle activity onset in the right arm as measured by EMG during this period that the arm was rotating, for the synchronous but not the asynchronous condition. A completely virtual object can therefore be experienced as part of one’s self, which opens up the possibility that an entire virtual body could be felt as one’s own in future virtual reality applications or online games, and be an invaluable tool for the understanding of the brain mechanisms underlying body ownership.

Mouth reversal extinguishes mismatch negativity induced by the McGurk illusion

DEFF Research Database (Denmark)

Eskelund, Kasper; Andersen, Tobias

2013-01-01

The sight of articulatory mouth movements (visual speech) influences auditory speech perception. This is demonstrated by the McGurk illusion in which incongruent visual speech alters the auditory phonetic percept. In behavioral studies, reversal of the vertical mouth direction has been reported...... by visual speech with either upright (unaltered) or vertically reversed mouth area. In a preliminary analysis, we found a Mismatch Negativity component induced by the McGurk illusion for 6 of 17 participants at electrode Cz when the mouth area was upright. In comparison, these participants produced...

The Pareidolia Test: A Simple Neuropsychological Test Measuring Visual Hallucination-Like Illusions

OpenAIRE

Mamiya, Yasuyuki; Nishio, Yoshiyuki; Watanabe, Hiroyuki; Yokoi, Kayoko; Uchiyama, Makoto; Baba, Toru; Iizuka, Osamu; Kanno, Shigenori; Kamimura, Naoto; Kazui, Hiroaki; Hashimoto, Mamoru; Ikeda, Manabu; Takeshita, Chieko; Shimomura, Tatsuo; Mori, Etsuro

2016-01-01

Background Visual hallucinations are a core clinical feature of dementia with Lewy bodies (DLB), and this symptom is important in the differential diagnosis and prediction of treatment response. The pareidolia test is a tool that evokes visual hallucination-like illusions, and these illusions may be a surrogate marker of visual hallucinations in DLB. We created a simplified version of the pareidolia test and examined its validity and reliability to establish the clinical utility of this test....

Nature's optics and our understanding of light

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Berry, M. V.

2015-01-01

Optical phenomena visible to everyone have been central to the development of, and abundantly illustrate, important concepts in science and mathematics. The phenomena considered from this viewpoint are rainbows, sparkling reflections on water, mirages, green flashes, earthlight on the moon, glories, daylight, crystals and the squint moon. And the concepts involved include refraction, caustics (focal singularities of ray optics), wave interference, numerical experiments, mathematical asymptotics, dispersion, complex angular momentum (Regge poles), polarisation singularities, Hamilton's conical intersections of eigenvalues ('Dirac points'), geometric phases and visual illusions.

Removal of proprioception by BCI raises a stronger body ownership illusion in control of a humanlike robot

OpenAIRE

Alimardani, Maryam; Nishio, Shuichi; Ishiguro, Hiroshi

2016-01-01

Body ownership illusions provide evidence that our sense of self is not coherent and can be extended to non-body objects. Studying about these illusions gives us practical tools to understand the brain mechanisms that underlie body recognition and the experience of self. We previously introduced an illusion of body ownership transfer (BOT) for operators of a very humanlike robot. This sensation of owning the robot?s body was confirmed when operators controlled the robot either by performing t...

Transcending the Self – the Illusion of Body Ownership in Immersive Virtual Reality and its Impact on Behaviour

Directory of Open Access Journals (Sweden)

Mel Slater

2011-10-01

Full Text Available Virtual reality in various forms has been around for about 40 years. It has been considered mainly as a technology that can be used to generate the illusion of a transformation of place. However, it has recently been shown that it can successfully be used to transcend the self, through illusions of body ownership and transformation. Several papers have shown that it is possible to generate in people the illusory sense of ownership of a fake body using virtual reality techniques [1-5]. This can be achieved through synchronous multisensory stimulation with respect to the real and virtual body. For example, the participant sees his or her virtual body touched, while feeling the touch synchronously and in the same place on the real body. This can also lead to illusions of body transformation, such as a thin person having the illusion of being fat [6]. Our research suggests the prime importance of a first person perspective for the illusion of ownership, however, in [7] we also found that a representation of a person in a virtual mirror with synchronous visual-motor effects also results in a body ownership illusion. Although virtual body ownership has been established, what is also of interest are the consequences of this in terms of the attitudes and behaviour of the participant who experiences the transformed body. Our very recent work suggests that the illusion of ownership of a virtual body may also result in at least short-term transformations of behaviour and attitudes of the participant towards those that are appropriate to the virtual body. This talk will describe several experiments illustrating both the illusion of body ownership and its transformative effect on attitudes and behaviour.

The spatial distance rule in the moving and classical rubber hand illusions.

Science.gov (United States)

Kalckert, Andreas; Ehrsson, H Henrik

2014-11-01

The rubber hand illusion (RHI) is a perceptual illusion in which participants perceive a model hand as part of their own body. Here, through the use of one questionnaire experiment and two proprioceptive drift experiments, we investigated the effect of distance (12, 27.5, and 43cm) in the vertical plane on both the moving and classical RHI. In both versions of the illusion, we found an effect of distance on ownership of the rubber hand for both measures tested. Our results further suggested that the moving RHI might follow a narrower spatial rule. Finally, whereas ownership of the moving rubber hand was affected by distance, this was not the case for agency, which was present at all distances tested. In sum, the present results generalize the spatial distance rule in terms of ownership to the vertical plane of space and demonstrate that also the moving RHI obeys this rule. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Perceiving a stranger's voice as being one's own: a 'rubber voice' illusion?

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Zane Z Zheng

2011-04-01

Full Text Available We describe an illusion in which a stranger's voice, when presented as the auditory concomitant of a participant's own speech, is perceived as a modified version of their own voice. When the congruence between utterance and feedback breaks down, the illusion is also broken. Compared to a baseline condition in which participants heard their own voice as feedback, hearing a stranger's voice induced robust changes in the fundamental frequency (F0 of their production. Moreover, the shift in F0 appears to be feedback dependent, since shift patterns depended reliably on the relationship between the participant's own F0 and the stranger-voice F0. The shift in F0 was evident both when the illusion was present and after it was broken, suggesting that auditory feedback from production may be used separately for self-recognition and for vocal motor control. Our findings indicate that self-recognition of voices, like other body attributes, is malleable and context dependent.

Symbol recognition produced by points of tactile stimulation: the illusion of linear continuity.

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Gonzales, G R

1996-11-01

To determine whether tactile receptive communication is possible through the use of a mechanical device that produces the phi phenomenon on the body surface. Twenty-six subjects (11 blind and 15 sighted participants) were tested with use of a tactile communication device (TCD) that produces an illusion of linear continuity forming numbers on the dorsal aspect of the wrist. Recognition of a number or number set was the goal. A TCD with protruding and vibrating solenoids produced sequentially delivered points of cutaneous stimulation along a pattern resembling numbers and created the illusion of dragging a vibrating stylet to form numbers, similar to what might be felt by testing for graphesthesia. Blind subjects recognized numbers with fewer trials than did sighted subjects, although all subjects were able to recognize all the numbers produced by the TCD. Subjects who had been blind since birth and had no prior tactile exposure to numbers were able to draw the numbers after experiencing them delivered by the TCD even though they did not recognize their meaning. The phi phenomenon is probably responsible for the illusion of continuous lines in the shape of numbers as produced by the TCD. This tactile illusion could potentially be used for more complex tactile communications such as letters and words.

Restoring tactile awareness through the rubber hand illusion in cervical spinal cord injury.

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Lenggenhager, Bigna; Scivoletto, Giorgio; Molinari, Marco; Pazzaglia, Mariella

2013-10-01

Bodily sensations are an important component of corporeal awareness. Spinal cord injury can leave affected body parts insentient and unmoving, leading to specific disturbances in the mental representation of one's own body and the sense of self. Here, we explored how illusions induced by multisensory stimulation influence immediate sensory signals and tactile awareness in patients with spinal cord injuries. The rubber hand illusion paradigm was applied to 2 patients with chronic and complete spinal cord injury of the sixth cervical spine, with severe somatosensory impairments in 2 of 5 fingers. Both patients experienced a strong illusion of ownership of the rubber hand during synchronous, but not asynchronous, stroking. They also, spontaneously reported basic tactile sensations in their previously numb fingers. Tactile awareness from seeing the rubber hand was enhanced by progressively increasing the stimulation duration. Multisensory illusions directly and specifically modulate the reemergence of sensory memories and enhance tactile sensation, despite (or as a result of) prior deafferentation. When sensory inputs are lost, and are later illusorily regained, the brain updates a coherent body image even several years after the body has become permanently unable to feel. This particular example of neural plasticity represents a significant opportunity to strengthen the sense of the self and the feelings of embodiment in patients with spinal cord injury.

Error and objectivity: cognitive illusions and qualitative research.

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Paley, John

2005-07-01

Psychological research has shown that cognitive illusions, of which visual illusions are just a special case, are systematic and pervasive, raising epistemological questions about how error in all forms of research can be identified and eliminated. The quantitative sciences make use of statistical techniques for this purpose, but it is not clear what the qualitative equivalent is, particularly in view of widespread scepticism about validity and objectivity. I argue that, in the light of cognitive psychology, the 'error question' cannot be dismissed as a positivist obsession, and that the concepts of truth and objectivity are unavoidable. However, they constitute only a 'minimal realism', which does not necessarily bring a commitment to 'absolute' truth, certainty, correspondence, causation, reductionism, or universal laws in its wake. The assumption that it does reflects a misreading of positivism and, ironically, precipitates a 'crisis of legitimation and representation', as described by constructivist authors.

A short educational intervention diminishes causal illusions and specific paranormal beliefs in undergraduates.

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Barberia, Itxaso; Tubau, Elisabet; Matute, Helena; Rodríguez-Ferreiro, Javier

2018-01-01

Cognitive biases such as causal illusions have been related to paranormal and pseudoscientific beliefs and, thus, pose a real threat to the development of adequate critical thinking abilities. We aimed to reduce causal illusions in undergraduates by means of an educational intervention combining training-in-bias and training-in-rules techniques. First, participants directly experienced situations that tend to induce the Barnum effect and the confirmation bias. Thereafter, these effects were explained and examples of their influence over everyday life were provided. Compared to a control group, participants who received the intervention showed diminished causal illusions in a contingency learning task and a decrease in the precognition dimension of a paranormal belief scale. Overall, results suggest that evidence-based educational interventions like the one presented here could be used to significantly improve critical thinking skills in our students.

A short educational intervention diminishes causal illusions and specific paranormal beliefs in undergraduates.

Directory of Open Access Journals (Sweden)

Itxaso Barberia

Full Text Available Cognitive biases such as causal illusions have been related to paranormal and pseudoscientific beliefs and, thus, pose a real threat to the development of adequate critical thinking abilities. We aimed to reduce causal illusions in undergraduates by means of an educational intervention combining training-in-bias and training-in-rules techniques. First, participants directly experienced situations that tend to induce the Barnum effect and the confirmation bias. Thereafter, these effects were explained and examples of their influence over everyday life were provided. Compared to a control group, participants who received the intervention showed diminished causal illusions in a contingency learning task and a decrease in the precognition dimension of a paranormal belief scale. Overall, results suggest that evidence-based educational interventions like the one presented here could be used to significantly improve critical thinking skills in our students.

More than a cool illusion? Functional significance of self-motion illusion (circular vection) for perspective switches.

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Riecke, Bernhard E; Feuereissen, Daniel; Rieser, John J; McNamara, Timothy P

2015-01-01

Self-motion can facilitate perspective switches and "automatic spatial updating" and help reduce disorientation in applications like virtual reality (VR). However, providing physical motion through moving-base motion simulators or free-space walking areas comes with high cost and technical complexity. This study provides first evidence that merely experiencing an embodied illusion of self-motion ("circular vection") can provide similar behavioral benefits as actual self-motion: Blindfolded participants were asked to imagine facing new perspectives in a well-learned room, and point to previously learned objects. Merely imagining perspective switches while stationary yielded worst performance. When perceiving illusory self-rotation to the novel perspective, however, performance improved significantly and yielded performance similar to actual rotation. Circular vection was induced by combining rotating sound fields ("auditory vection") and biomechanical vection from stepping along a carrousel-like rotating floor platter. In sum, illusory self-motion indeed facilitated perspective switches and thus spatial orientation, similar to actual self-motion, thus providing first compelling evidence of the functional significance and behavioral relevance of vection. This could ultimately enable us to complement the prevailing introspective vection measures with behavioral indicators, and guide the design for more affordable yet effective VR simulators that intelligently employ multi-modal self-motion illusions to reduce the need for costly physical observer motion.

3D Viewing: Odd Perception - Illusion? reality? or both?

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Kisimoto, K.; Iizasa, K.

2008-12-01

We live in the three dimensional space, don't we? It could be at least four dimensions, but that is another story. In either way our perceptual capability of 3D-Viewing is constrained by our 2D-perception (our intrinsic tools of perception). I carried out a few visual experiments using topographic data to show our intrinsic (or biological) disability (or shortcoming) in 3D-recognition of our world. Results of the experiments suggest: (1) 3D-surface model displayed on a 2D-computer screen (or paper) always has two interpretations of the 3D- surface geometry, if we choose one of the interpretation (in other word, if we are hooked by one perception of the two), we maintain its perception even if the 3D-model changes its viewing perspective in time shown on the screen, (2) more interesting is that 3D-real solid object (e.g.,made of clay) also gives above mentioned two interpretations of the geometry of the object, if we observe the object with one-eye. Most famous example of this viewing illusion is exemplified by a magician, who died in 2007, Jerry Andrus who made a super-cool paper crafted dragon which causes visual illusion to one-eyed viewer. I, by the experiments, confirmed this phenomenon in another perceptually persuasive (deceptive?) way. My conclusion is that this illusion is intrinsic, i.e. reality for human, because, even if we live in 3D-space, our perceptional tool (eyes) is composed of 2D sensors whose information is reconstructed or processed to 3D by our experience-based brain. So, (3) when we observe the 3D-surface-model on the computer screen, we are always one eye short even if we use both eyes. One last suggestion from my experiments is that recent highly sophisticated 3D- models might include too many information that human perceptions cannot handle properly, i.e. we might not be understanding the 3D world (geospace) at all, just illusioned.

Cortical evoked potentials to an auditory illusion: binaural beats.

Science.gov (United States)

Pratt, Hillel; Starr, Arnold; Michalewski, Henry J; Dimitrijevic, Andrew; Bleich, Naomi; Mittelman, Nomi

2009-08-01

To define brain activity corresponding to an auditory illusion of 3 and 6Hz binaural beats in 250Hz or 1000Hz base frequencies, and compare it to the sound onset response. Event-Related Potentials (ERPs) were recorded in response to unmodulated tones of 250 or 1000Hz to one ear and 3 or 6Hz higher to the other, creating an illusion of amplitude modulations (beats) of 3Hz and 6Hz, in base frequencies of 250Hz and 1000Hz. Tones were 2000ms in duration and presented with approximately 1s intervals. Latency, amplitude and source current density estimates of ERP components to tone onset and subsequent beats-evoked oscillations were determined and compared across beat frequencies with both base frequencies. All stimuli evoked tone-onset P(50), N(100) and P(200) components followed by oscillations corresponding to the beat frequency, and a subsequent tone-offset complex. Beats-evoked oscillations were higher in amplitude with the low base frequency and to the low beat frequency. Sources of the beats-evoked oscillations across all stimulus conditions located mostly to left lateral and inferior temporal lobe areas in all stimulus conditions. Onset-evoked components were not different across stimulus conditions; P(50) had significantly different sources than the beats-evoked oscillations; and N(100) and P(200) sources located to the same temporal lobe regions as beats-evoked oscillations, but were bilateral and also included frontal and parietal contributions. Neural activity with slightly different volley frequencies from left and right ear converges and interacts in the central auditory brainstem pathways to generate beats of neural activity to modulate activities in the left temporal lobe, giving rise to the illusion of binaural beats. Cortical potentials recorded to binaural beats are distinct from onset responses. Brain activity corresponding to an auditory illusion of low frequency beats can be recorded from the scalp.

Combined visual illusion effects on the perceived index of difficulty and movement outcomes in discrete and continuous fitts' tapping.

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Alphonsa, Sushma; Dai, Boyi; Benham-Deal, Tami; Zhu, Qin

2016-01-01

The speed-accuracy trade-off is a fundamental movement problem that has been extensively investigated. It has been established that the speed at which one can move to tap targets depends on how large the targets are and how far they are apart. These spatial properties of the targets can be quantified by the index of difficulty (ID). Two visual illusions are known to affect the perception of target size and movement amplitude: the Ebbinghaus illusion and Muller-Lyer illusion. We created visual images that combined these two visual illusions to manipulate the perceived ID, and then examined people's visual perception of the targets in illusory context as well as their performance in tapping those targets in both discrete and continuous manners. The findings revealed that the combined visual illusions affected the perceived ID similarly in both discrete and continuous judgment conditions. However, the movement outcomes were affected by the combined visual illusions according to the tapping mode. In discrete tapping, the combined visual illusions affected both movement accuracy and movement amplitude such that the effective ID resembled the perceived ID. In continuous tapping, none of the movement outcomes were affected by the combined visual illusions. Participants tapped the targets with higher speed and accuracy in all visual conditions. Based on these findings, we concluded that distinct visual-motor control mechanisms were responsible for execution of discrete and continuous Fitts' tapping. Although discrete tapping relies on allocentric information (object-centered) to plan for action, continuous tapping relies on egocentric information (self-centered) to control for action. The planning-control model for rapid aiming movements is supported.

Klubi Illusion toob Tartusse New Yorgi ja Londoni / Riho Laurisaar

Index Scriptorium Estoniae

Laurisaar, Riho

2006-01-01

Stalini-aegses kinohoones Tartus avati suurlinlik klubi "Illusion". Sisekujunduses pole jälgitud kindlat stiili, koos on kitsh ja glamuur, klassika ja ajalooline arhitektuur. Sisearhitekt Jaanis Ilves

Psychosis-proneness and the rubber hand illusion of body ownership.

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Germine, Laura; Benson, Taylor Leigh; Cohen, Francesca; Hooker, Christine I'lee

2013-05-15

Psychosis and psychosis-proneness are associated with abnormalities in subjective experience of the self, including distortions in bodily experience that are difficult to study experimentally due to lack of structured methods. In 55 healthy adults, we assessed the relationship between self-reported psychosis-like characteristics and susceptibility to the rubber hand illusion of body ownership. In this illusion, a participant sees a rubber hand being stroked by a brush at the same time that they feel a brush stroking their own hand. In some individuals, this creates the bodily sense that the rubber hand is their own hand. Individual differences in positive (but not negative) psychosis-like characteristics predicted differences in susceptibility to experiencing the rubber hand illusion. This relationship was specific to the subjective experience of rubber hand ownership, and not other unusual experiences or sensations, and absent when a small delay was introduced between seeing and feeling the brush stroke. This indicates that individual differences in susceptibility are related to visual-tactile integration and cannot be explained by differences in the tendency to endorse unusual experiences. Our findings suggest that susceptibility to body representation distortion by sensory information may be related or contribute to the development of psychosis and positive psychosis-like characteristics. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Cosmic acceleration as an optical illusion

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Skarke, Harald

2017-03-01

We consider light propagation in an inhomogeneous irrotational dust universe with vanishing cosmological constant, with initial conditions as in standard linear perturbation theory. A non-perturbative approach to the dynamics of such a universe is combined with a distance formula based on the Sachs optical equations. Then a numerical study implies a redshift-distance relation that roughly agrees with observations. Interpreted in the standard homogeneous setup, our results would appear to imply the currently accepted values for the Hubble rate and the deceleration parameter; furthermore there is consistency with density perturbations at last scattering. The determination of these three quantities relies only on a single parameter related to a cutoff scale. Discrepancies with the existing literature are related to subtleties of higher order perturbation theory which make both the reliability of the present approach and the magnitude of perturbative effects beyond second order hard to assess.

Cosmic acceleration as an optical illusion

International Nuclear Information System (INIS)

Skarke, Harald

2017-01-01

We consider light propagation in an inhomogeneous irrotational dust universe with vanishing cosmological constant, with initial conditions as in standard linear perturbation theory. A non-perturbative approach to the dynamics of such a universe is combined with a distance formula based on the Sachs optical equations. Then a numerical study implies a redshift-distance relation that roughly agrees with observations. Interpreted in the standard homogeneous setup, our results would appear to imply the currently accepted values for the Hubble rate and the deceleration parameter; furthermore there is consistency with density perturbations at last scattering. The determination of these three quantities relies only on a single parameter related to a cutoff scale. Discrepancies with the existing literature are related to subtleties of higher order perturbation theory which make both the reliability of the present approach and the magnitude of perturbative effects beyond second order hard to assess. (orig.)

The Effect of Interacting with Two Devices when Creating the Illusion of Internal State in Tangible Widgets

DEFF Research Database (Denmark)

Bech, Christoffer; Bork, Andreas Heldbjerg; Memborg, Jakob Birch

2017-01-01

This paper investigates whether the illusion of internal state in passive tangible widgets is stronger when using one touchscreen device or two devices. Passive tangible widgets are an increasingly popular way to interact with tablet games. Since the production of passive widgets is usually cheaper...... than the production of widgets with internal state, it is much more cost-efficient to induce the illusion of internal state in passive widgets than to use tangible widgets with an actual internal state. An experiment was conducted where the participants’ belief in the illusion was determined by means...

The McGurk Illusion in the Oddity Task

DEFF Research Database (Denmark)

Andersen, Tobias

2010-01-01

Despite many studies of audiovisual integration in speech perception very few studies have addressed the issue of cross- modal response bias. Using synthetic acoustic speech, the current study demonstrates the McGurk illusion in the oddity task which is not prone to cross-modal response bias...

The functional subdivision of the visual brain: Is there a real illusion effect on action? A multi-lab replication study.

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Kopiske, Karl K; Bruno, Nicola; Hesse, Constanze; Schenk, Thomas; Franz, Volker H

2016-06-01

It has often been suggested that visual illusions affect perception but not actions such as grasping, as predicted by the "two-visual-systems" hypothesis of Milner and Goodale (1995, The Visual Brain in Action, Oxford University press). However, at least for the Ebbinghaus illusion, relevant studies seem to reveal a consistent illusion effect on grasping (Franz & Gegenfurtner, 2008. Grasping visual illusions: consistent data and no dissociation. Cognitive Neuropsychology). Two interpretations are possible: either grasping is not immune to illusions (arguing against dissociable processing mechanisms for vision-for-perception and vision-for-action), or some other factors modulate grasping in ways that mimic a vision-for perception effect in actions. It has been suggested that one such factor may be obstacle avoidance (Haffenden Schiff & Goodale, 2001. The dissociation between perception and action in the Ebbinghaus illusion: nonillusory effects of pictorial cues on grasp. Current Biology, 11, 177-181). In four different labs (total N = 144), we conducted an exact replication of previous studies suggesting obstacle avoidance mechanisms, implementing conditions that tested grasping as well as multiple perceptual tasks. This replication was supplemented by additional conditions to obtain more conclusive results. Our results confirm that grasping is affected by the Ebbinghaus illusion and demonstrate that this effect cannot be explained by obstacle avoidance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Does my step look big in this? A visual illusion leads to safer stepping behaviour.

Directory of Open Access Journals (Sweden)

David B Elliott

Full Text Available BACKGROUND: Tripping is a common factor in falls and a typical safety strategy to avoid tripping on steps or stairs is to increase foot clearance over the step edge. In the present study we asked whether the perceived height of a step could be increased using a visual illusion and whether this would lead to the adoption of a safer stepping strategy, in terms of greater foot clearance over the step edge. The study also addressed the controversial question of whether motor actions are dissociated from visual perception. METHODOLOGY/PRINCIPAL FINDINGS: 21 young, healthy subjects perceived the step to be higher in a configuration of the horizontal-vertical illusion compared to a reverse configuration (p = 0.01. During a simple stepping task, maximum toe elevation changed by an amount corresponding to the size of the visual illusion (p<0.001. Linear regression analyses showed highly significant associations between perceived step height and maximum toe elevation for all conditions. CONCLUSIONS/SIGNIFICANCE: The perceived height of a step can be manipulated using a simple visual illusion, leading to the adoption of a safer stepping strategy in terms of greater foot clearance over a step edge. In addition, the strong link found between perception of a visual illusion and visuomotor action provides additional support to the view that the original, controversial proposal by Goodale and Milner (1992 of two separate and distinct visual streams for perception and visuomotor action should be re-evaluated.

Georges Sagnac: A life for optics

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Darrigol, Olivier

2014-12-01

Georges Sagnac is mostly known for the optical effect in rotating frames that he demonstrated in 1913. His scientific interests were quite diverse: they included photography, optical illusions, X-ray physics, radioactivity, the blue of the sky, anomalous wave propagation, interferometry, strioscopy, and acoustics. An optical theme nonetheless pervaded his entire œuvre. Within optics, an original theory of the propagation of light motivated most of his investigations, from an ingenious explanation of the Fresnel drag, through the discovery of the Sagnac effect, to his quixotic defense of an alternative to relativity theory. Optical analogies efficiently guided his work in other domains. Optics indeed was his true passion. He saw himself as carrying the torch of the two great masters of French optics, Augustin Fresnel and Hippolyte Fizeau. In this mission he overcame his poor health and labored against the modernist tide, with much success originally and bitter isolation in the end. xml:lang="fr"

Characterizing Illusions of Competence in Introductory Chemistry Students

Science.gov (United States)

Pazicni, Samuel; Bauer, Christopher F.

2014-01-01

The Dunning-Kruger effect is a cognitive bias that plagues a particular population of students--the unskilled. This population suffers from illusory competence, as determined by inaccurate ratings of their own ability/performance. These mistakenly high self-ratings (i.e. ''illusions of competence'') are typically explained by a metacognitive…

Inflation and Stock Prices: No Illusion

OpenAIRE

Chao Wei

2007-01-01

Campbell and Vuolteenaho (2004) use VAR results to advocate inflation illusion as the explanation for the positive association between inflation and the dividend yield. Contrary to their results, we find that a fully rational dynamic general equilibrium model can generate a positive correlation between the dividend yield and inflation of comparable size to its data counterpart. The model results support a proxy hypothesis, according to which, a third factor, which in our model represents tech...

Far-field high resolution effects and manipulating of electromagnetic waves based on transformation optics

Science.gov (United States)

Ji, XueBin; Zang, XiaoFei; Li, Zhou; Shi, Cheng; Chen, Lin; Cai, Bin; Zhu, YiMing

2015-05-01

Based on the transformation optics (TO) and the effective medium theory (EMT), a new illusion media with homogeneous and isotropic materials is proposed to realize the far-field high resolution effects. When two point sources with the separation distance of λ0 / 4 are covered with the illusion media (λ0 is the free-space wavelength), the corresponding far-field pattern is equivalent to the case of two point sources with the separation distance larger than λ0 / 2 in free space, leading to the far-field high resolution effects (in free space, the separation distance of λ0 / 4 is less than half-wavelength, and thus the two point sources cannot be distinguished from each other). Furthermore, such illusion media can be applied to design tunable high-directivity antenna and an angle-dependent floating carpet cloak. Full wave simulations are carried out to verify the performance of our device.

More than a Cool Illusion? Functional Significance of Self-Motion Illusion (Circular Vection for Perspective Switches

Directory of Open Access Journals (Sweden)

Bernhard E. Riecke

2015-08-01

Full Text Available Self-motion can facilitate perspective switches and automatic spatial updating and help reduce disorientation in applications like Virtual Reality. However, providing physical motion through moving-base motion simulators or free-space walking areas comes with high cost and technical complexity. This study provides first evidence that merely experiencing an embodied illusion of self-motion (circular vection can provide similar behavioral benefits as actual self-motion: Blindfolded participants were asked to imagine facing new perspectives in a well-learned room, and point to previously-learned objects. Merely imagining perspective switches while stationary yielded worst performance. When perceiving illusory self-rotation to the novel perspective, however, performance improved significantly and yielded performance similar to actual rotation. Circular vection was induced by combining rotating sound fields (auditory vection and biomechanical vection from stepping along a carrousel-like rotating floor platter. In sum, illusory self-motion indeed facilitated perspective switches and thus spatial orientation, similar to actual self-motion, thus providing first compelling evidence of the functional significance and behavioral relevance of vection. This could ultimately enable us to complement the prevailing introspective vection measures with behavioral indicators, and guide the design for more affordable yet effective Virtual Reality simulators that intelligently employ multi-modal self-motion illusions to reduce the need for costly physical observer motion.

Medically unexplained symptom reports are associated with a decreased response to the rubber hand illusion.

Science.gov (United States)

Miles, Eleanor; Poliakoff, Ellen; Brown, Richard J

2011-10-01

Medically unexplained symptoms (MUS) have been hypothesized to result from a distortion in perception, whereby top-down factors influence the process of body representation. Perceptual illusions provide a novel method of investigating this hypothesis. This study aimed to investigate whether self-reported unexplained symptoms are associated with altered experience of the rubber hand illusion (RHI). A non-clinical MUS group with high scores on the Somatoform Dissociation Questionnaire (SDQ), and a control group with low scores on this scale, were exposed to the RHI. Illusion experience was measured by self-reports and by proprioceptive alteration. After controlling for somatosensory amplification and trait anxiety, the low-SDQ group responded significantly more strongly to the RHI on both questionnaire and proprioceptive measures of the illusion. In contrast, the high-SDQ group scored significantly higher on the Perceptual Aberrations Scale, a measure of bodily distortions in daily life. These findings support the proposed link between MUS and disturbances in body representation, and suggest that a decreased reliance on current sensory inputs may contribute to symptom experience in susceptible individuals. Copyright © 2011 Elsevier Inc. All rights reserved.

Maximizing the optical network capacity.

Science.gov (United States)

Bayvel, Polina; Maher, Robert; Xu, Tianhua; Liga, Gabriele; Shevchenko, Nikita A; Lavery, Domaniç; Alvarado, Alex; Killey, Robert I

2016-03-06

Most of the digital data transmitted are carried by optical fibres, forming the great part of the national and international communication infrastructure. The information-carrying capacity of these networks has increased vastly over the past decades through the introduction of wavelength division multiplexing, advanced modulation formats, digital signal processing and improved optical fibre and amplifier technology. These developments sparked the communication revolution and the growth of the Internet, and have created an illusion of infinite capacity being available. But as the volume of data continues to increase, is there a limit to the capacity of an optical fibre communication channel? The optical fibre channel is nonlinear, and the intensity-dependent Kerr nonlinearity limit has been suggested as a fundamental limit to optical fibre capacity. Current research is focused on whether this is the case, and on linear and nonlinear techniques, both optical and electronic, to understand, unlock and maximize the capacity of optical communications in the nonlinear regime. This paper describes some of them and discusses future prospects for success in the quest for capacity. © 2016 The Authors.

Evaluation for the design of experience in virtual environments: modeling breakdown of interaction and illusion.

Science.gov (United States)

Marsh, T; Wright, P; Smith, S

2001-04-01

New and emerging media technologies have the potential to induce a variety of experiences in users. In this paper, it is argued that the inducement of experience presupposes that users are absorbed in the illusion created by these media. Looking to another successful visual medium, film, this paper borrows from the techniques used in "shaping experience" to hold spectators' attention in the illusion of film, and identifies what breaks the illusion/experience for spectators. This paper focuses on one medium, virtual reality (VR), and advocates a transparent or "invisible style" of interaction. We argue that transparency keeps users in the "flow" of their activities and consequently enhances experience in users. Breakdown in activities breaks the experience and subsequently provides opportunities to identify and analyze potential causes of usability problems. Adopting activity theory, we devise a model of interaction with VR--through consciousness and activity--and introduce the concept of breakdown in illusion. From this, a model of effective interaction with VR is devised and the occurrence of breakdown in interaction and illusion is identified along a continuum of engagement. Evaluation guidelines for the design of experience are proposed and applied to usability problems detected in an empirical study of a head-mounted display (HMD) VR system. This study shows that the guidelines are effective in the evaluation of VR. Finally, we look at the potential experiences that may be induced in users and propose a way to evaluate user experience in virtual environments (VEs) and other new and emerging media.

The neural signature of the Fraser illusion: An explorative EEG study on Fraser-like displays

Directory of Open Access Journals (Sweden)

Xuyan eYun

2015-07-01

Full Text Available We studied neural correlates accompanying the Fraser spiral illusion. The Fraser spiral illusion consists of twisted cords superimposed on a patchwork background arranged in concentric circles, which is typically perceived as a spiral. We tested four displays: the Fraser spiral illusion and three variants derived from it by orthogonally combining featural properties. In our stimuli, the shape of the cords comprised either concentric circles or a single spiral. The cords themselves consisted of black and white lines in parallel to the contour of the cords (i.e. parallel cords, or oblique line elements (i.e. twisted cords. The displays with twisted cords successfully induced illusory percepts, i.e. circles looked like spirals (the Fraser spiral illusion and spirals looked like circles (i.e., a ‘reverse Fraser illusion’. We compared the event-related potentials in a Stimulus (Circle, Spiral × Percept (Circle, Spiral design. A significant main effect of Stimulus was found at the posterior scalp in an early component (P220-280 and a significant main effect of Percept was found over the anterior scalp in a later component (P350-450. Although the EEG data suggest stimulus-based processing in posterior area in an early time window and Percept based processing in the later time window, an overall clear-cut stimulus-percept segregation was not found due to additional interaction effects. Instead, the data, especially in the later time window in the anterior area, point at differential processing for the condition comprising circle shapes but spiral percepts (i.e. the Fraser illusion.

Empathy in intimate relationships : The role of positive illusions

NARCIS (Netherlands)

Dijkstra, Pieternel; Barelds, Dick P.H.; Groothof, Hinke A.K.; Van Bruggen, Marnix

2014-01-01

Previous studies have shown empathy to be an important aspect of a high quality intimate relationship. Likewise, positive illusions about a partner's characteristics have been shown to contribute to relationship quality. The present study connects these issues by examining the degree to which

Visual illusions and direct perception : Elaborating on Gibson's insights

NARCIS (Netherlands)

de Wit, Matthieu M.; van der Kamp, John; Withagen, Rob

Gibson argued that illusory pictorial displays contain "inadequate" information (1966, p. 288) but also that a "very special kind of selective attention" (p.313) can dispel the illusion -suggesting that adequate perceptual information could in fact be potentially available to observers. The present

Visual illusions and direct perception: Elaborating on Gibson's insights

NARCIS (Netherlands)

de Wit, M.M.; van der Kamp, J.; Withagen, R

2015-01-01

Gibson argued that illusory pictorial displays contain "inadequate" information (1966, p. 288) but also that a "very special kind of selective attention" (p. 313) can dispel the illusion-suggesting that adequate perceptual information could in fact be potentially available to observers. The present

The rubber hand illusion in complex regional pain syndrome: preserved ability to integrate a rubber hand indicates intact multisensory integration.

Science.gov (United States)

Reinersmann, Annika; Landwehrt, Julia; Krumova, Elena K; Peterburs, Jutta; Ocklenburg, Sebastian; Güntürkün, Onur; Maier, Christoph

2013-09-01

In patients with complex regional pain syndrome (CRPS) type 1, processing of static tactile stimuli is impaired, whereas more complex sensory integration functions appear preserved. This study investigated higher order multisensory integration of body-relevant stimuli using the rubber hand illusion in CRPS patients. Subjective self-reports and skin conductance responses to watching the rubber hand being harmed were compared among CRPS patients (N=24), patients with upper limb pain of other origin (N=21, clinical control group), and healthy subjects (N=24). Additionally, the influence of body representation (body plasticity [Trinity Assessment of Body Plasticity], neglect-like severity symptoms), and clinical signs of illusion strength were investigated. For statistical analysis, 1-way analysis of variance, t test, Pearson correlation, with α=0.05 were used. CRPS patients did not differ from healthy subjects and the control group with regard to their illusion strength as assessed by subjective reports or skin conductance response values. Stronger left-sided rubber hand illusions were reported by healthy subjects and left-side-affected CRPS patients. Moreover, for this subgroup, illness duration and illusion strength were negatively correlated. Overall, severity of neglect-like symptoms and clinical signs were not related to illusion strength. However, patients with CRPS of the right hand reported significantly stronger neglect-like symptoms and significantly lower illusion strength of the affected hand than patients with CRPS of the left hand. The weaker illusion of CRPS patients with strong neglect-like symptoms on the affected hand supports the role of top-down processes modulating body ownership. Moreover, the intact ability to perceive illusory ownership confirms the notion that, despite impaired processing of proprioceptive or tactile input, higher order multisensory integration is unaffected in CRPS. Copyright © 2013 International Association for the Study

Modulation of fronto-parietal connections during the rubber hand illusion

DEFF Research Database (Denmark)

Karabanov, Anke Ninija; Ritterband-Rosenbaum, Anina; Christensen, Mark Schram

2017-01-01

Accumulating evidence suggests that parieto-frontal connections play a role in adjusting body ownership during the Rubber Hand Illusion (RHI). Using a motor version of the rubber hand illusion paradigm, we applied single-site and dual-site transcranial magnetic stimulation (TMS) to investigate...... and during three RHI conditions: a) agency and ownership, b) agency but no ownership and c) neither agency nor ownership. Parietal-motor communication differed among experimental conditions. The induction of action ownership was associated with an inhibitory parietal-to-motor connectivity, which...... cortico-spinal and parietal-frontal connectivity during perceived rubber hand ownership. Healthy volunteers received a conditioning TMS pulse over left anterior intraparietal sulcus (aIPS) and a test TMS pulse over left primary motor cortex (M1). Motor Evoked Potentials (MEPs) were recorded at rest...

Motor imagery enhancement paradigm using moving rubber hand illusion system.

Science.gov (United States)

Minsu Song; Jonghyun Kim

2017-07-01

Motor imagery (MI) has been widely used in neurorehabilitation and brain computer interface. The size of event-related desynchronization (ERD) is a key parameter for successful motor imaginary rehabilitation and BCI adaptation. Many studies have used visual guidance for enhancement/ amplification of motor imagery ERD amplitude, but their enhancements were not significant. We propose a novel ERD enhancing paradigm using body-ownership illusion, or also known as rubber hand illusion (RHI). The system was made by motorized, moving rubber hand which can simulate wrist extension. The amplifying effects of the proposed RHI paradigm were evaluated by comparing ERD sizes of the proposed paradigm with motor imagery and actual motor execution paradigms. The comparison result shows that the improvement of ERD size due to the proposed paradigm was statistically significant (pparadigms.

Using visuo-kinetic virtual reality to induce illusory spinal movement: the MoOVi Illusion

OpenAIRE

Harvie, Daniel S.; Smith, Ross T.; Hunter, Estin V.; Davis, Miles G.; Sterling, Michele; Moseley, G. Lorimer

2017-01-01

Background Illusions that alter perception of the body provide novel opportunities to target brain-based contributions to problems such as persistent pain. One example of this, mirror therapy, uses vision to augment perceived movement of a painful limb to treat pain. Since mirrors can’t be used to induce augmented neck or other spinal movement, we aimed to test whether such an illusion could be achieved using virtual reality, in advance of testing its potential therapeutic benefit. We hypothe...

Conditioned pain modulation dampens the thermal grill illusion.

Science.gov (United States)

Harper, D E; Hollins, M

2017-10-01

The thermal grill illusion (TGI) refers to the perception of burning heat and often pain that arises from simultaneous cutaneous application of innocuous warm and cool stimuli. This study utilized conditioned pain modulation (CPM) to help elucidate the TGI's underlying neural mechanisms, including the debated role of ascending nociceptive signals in generating the illusion. To trigger CPM, subjects placed the left hand in noxious cold (6 °C) water before placing the right volar forearm onto a thermal grill. Lower pain and unpleasantness ratings of the grill in this CPM run compared to those in a control run (i.e. 33 °C water) were taken as evidence of CPM. To determine whether CPM reduces noxious heat pain and illusory heat pain equally, an experimental group of subjects rated pain and unpleasantness of a grill consisting of innocuous alternating warm (42 °C) and cool (18 °C) bars, while a control group rated a grill with all bars controlled to a noxious temperature (45 °C). CPM produced significant and comparable reductions in pain, unpleasantness and perceived heat of both noxious heat and the TGI. This result suggests that the TGI results from signals in nociceptive dorsal horn convergent neurons, since CPM involves descending inhibition with high selectivity for this neuronal population. More broadly, CPM's ability to produce a shift in perceived thermal sensation of both noxious heat and the TGI from 'hot' to 'warm' implies that nociceptive signals generated by a cutaneous stimulus can contribute to its perceived thermal intensity. Conditioned pain modulation reduces the perceived painfulness, unpleasantness and heat of the thermal grill illusion and noxious heat similarly. The results have important theoretical implications for both types of pain. © 2017 European Pain Federation - EFIC®.

Knowing the Limits of One's Understanding: The Development of an Awareness of an Illusion of Explanatory Depth

Science.gov (United States)

Mills, Candice M.; Keil, Frank C.

2004-01-01

Adults overestimate the detail and depth of their explanatory knowledge, but through providing explanations they recognize their initial illusion of understanding. By contrast, they are much more accurate in making self-assessments for other kinds of knowledge, such as for procedures, narratives, and facts. Two studies examined this "illusion of…

Integration eller Illusion

DEFF Research Database (Denmark)

Rezaei, Shahamak; Goli, Marco

2012-01-01

Integration or illusion – a deviance perspective Denmark experienced one of its most successful periods of economic growth in 2004–2008 with a tremendous reduction of unemployment, which in June 2008 was around. 1.5 percent, far below the expected level of structural unemployment. In the wake...... of migrants’ skills. 2. Whether there were patterns of over-education as expression of institutional and societal discrimination. The focus of the present study is, however, quite different: We examine the pattern of deviance in relation to labour market participation (not integration), and instead...... of searching for explanations for the lack of integration, we attempt to identify and explain the deviance pattern as a product of institutionally inherent possibilities and barriers on the one hand and articulating immigrants as rational actors (not victims) on the other. We argue that deviance is not only...

Applying the Helmholtz Illusion to Fashion: Horizontal Stripes Won't Make You Look Fatter

Directory of Open Access Journals (Sweden)

Peter Thompson

2011-01-01

Full Text Available A square composed of horizontal lines appears taller and narrower than an identical square made up of vertical lines. Reporting this illusion, Hermann von Helmholtz noted that such illusions, in which filled space seems to be larger than unfilled space, were common in everyday life, adding the observation that ladies' frocks with horizontal stripes make the figure look taller. As this assertion runs counter to modern popular belief, we have investigated whether vertical or horizontal stripes on clothing should make the wearer appear taller or fatter. We find that a rectangle of vertical stripes needs to be extended by 7.1% vertically to match the height of a square of horizontal stripes and that a rectangle of horizontal stripes must be made 4.5% wider than a square of vertical stripes to match its perceived width. This illusion holds when the horizontal or vertical lines are on the dress of a line drawing of a woman. We have examined the claim that these effects apply only for 2-dimensional figures in an experiment with 3-D cylinders and find no support for the notion that horizontal lines would be ‘fattening’ on clothes. Significantly, the illusion persists when the horizontal or vertical lines are on pictures of a real half-body mannequin viewed stereoscopically. All the evidence supports Helmholtz's original assertion.

The effect of working memory load on semantic illusions: what the phonological loop and central executive have to contribute.

Science.gov (United States)

Büttner, Anke Caroline

2012-01-01

When asked how many animals of each kind Moses took on the Ark, most people respond with "two" despite the substituted name (Moses for Noah) in the question. Possible explanations for semantic illusions appear to be related to processing limitations such as those of working memory. Indeed, individual working memory capacity has an impact upon how sentences containing substitutions are processed. This experiment examined further the role of working memory in the occurrence of semantic illusions using a dual-task working memory load approach. Participants verified statements while engaging in either articulatory suppression or random number generation. Secondary task type had a significant effect on semantic illusion rate, but only when comparing the control condition to the two dual-task conditions. Furthermore, secondary task performance in the random number generation condition declined, suggesting a tradeoff between tasks. Response time analyses also showed a different pattern of processing across the conditions. The findings suggest that the phonological loop plays a role in representing semantic illusion sentences coherently and in monitoring for details, while the role of the central executive is to assist gist-processing of sentences. This usually efficient strategy leads to error in the case of semantic illusions.

Perception, action, and Roelofs effect: a mere illusion of dissociation.

Directory of Open Access Journals (Sweden)

Paul Dassonville

2004-11-01

Full Text Available A prominent and influential hypothesis of vision suggests the existence of two separate visual systems within the brain, one creating our perception of the world and another guiding our actions within it. The induced Roelofs effect has been described as providing strong evidence for this perception/action dissociation: When a small visual target is surrounded by a large frame positioned so that the frame's center is offset from the observer's midline, the perceived location of the target is shifted in the direction opposite the frame's offset. In spite of this perceptual mislocalization, however, the observer can accurately guide movements to the target location. Thus, perception is prone to the illusion while actions seem immune. Here we demonstrate that the Roelofs illusion is caused by a frame-induced transient distortion of the observer's apparent midline. We further demonstrate that actions guided to targets within this same distorted egocentric reference frame are fully expected to be accurate, since the errors of target localization will exactly cancel the errors of motor guidance. These findings provide a mechanistic explanation for the various perceptual and motor effects of the induced Roelofs illusion without requiring the existence of separate neural systems for perception and action. Given this, the behavioral dissociation that accompanies the Roelofs effect cannot be considered evidence of a dissociation of perception and action. This indicates a general need to re-evaluate the broad class of evidence purported to support this hypothesized dissociation.

Lighting, backlighting and watercolor illusions and the laws of figurality.

Science.gov (United States)

Pinna, Baingio; Reeves, Adam

2006-01-01

We report some novel 'lighting' and 'backlighting' effects in plane figures similar to those which induce the 'watercolor illusion', that is, figures made with outlines composed of juxtaposed parallel lines varying in brightness and chromatic color. These new effects show 'illumination' as an emergent percept, and show how arrangements of 'dark and light' along the boundaries of various plane figures model the volume and strengthen the illusion of depth. To account for these various effects we propose several phenomenological 'laws of figurality' to add to the Gestalt laws of organization and figure-ground segregation. We offer a set of meta-laws which are speculative but which serve to integrate and organize the phenomenological laws. These laws indicate how luminance gradient profiles across boundary contours define both the 3D appearance of figures and the properties of the light reflected from their volumetric shapes.

Sleeping on the rubber-hand illusion: Memory reactivation during sleep facilitates multisensory recalibration.

Science.gov (United States)

Honma, Motoyasu; Plass, John; Brang, David; Florczak, Susan M; Grabowecky, Marcia; Paller, Ken A

2016-01-01

Plasticity is essential in body perception so that physical changes in the body can be accommodated and assimilated. Multisensory integration of visual, auditory, tactile, and proprioceptive signals contributes both to conscious perception of the body's current state and to associated learning. However, much is unknown about how novel information is assimilated into body perception networks in the brain. Sleep-based consolidation can facilitate various types of learning via the reactivation of networks involved in prior encoding or through synaptic down-scaling. Sleep may likewise contribute to perceptual learning of bodily information by providing an optimal time for multisensory recalibration. Here we used methods for targeted memory reactivation (TMR) during slow-wave sleep to examine the influence of sleep-based reactivation of experimentally induced alterations in body perception. The rubber-hand illusion was induced with concomitant auditory stimulation in 24 healthy participants on 3 consecutive days. While each participant was sleeping in his or her own bed during intervening nights, electrophysiological detection of slow-wave sleep prompted covert stimulation with either the sound heard during illusion induction, a counterbalanced novel sound, or neither. TMR systematically enhanced feelings of bodily ownership after subsequent inductions of the rubber-hand illusion. TMR also enhanced spatial recalibration of perceived hand location in the direction of the rubber hand. This evidence for a sleep-based facilitation of a body-perception illusion demonstrates that the spatial recalibration of multisensory signals can be altered overnight to stabilize new learning of bodily representations. Sleep-based memory processing may thus constitute a fundamental component of body-image plasticity.

Effect of field-of-view on the Coriolis illusion

NARCIS (Netherlands)

Groen, E.L.; Muis, H.; Kooi, F.L.

2008-01-01

Tilting the head during rotation about an Earth-vertical axis produces cross-coupled stimulation of the semicircular canals. Without visual feedback on the actual self-motion, this leads to the so-called Coriolis illusion. We investigated the effect of the field-of-view (FOV) on the magnitude and

Auralization of CFD Vorticity Using an Auditory Illusion

Science.gov (United States)

Volpe, C. R.

2005-12-01

One way in which scientists and engineers interpret large quantities of data is through a process called visualization, i.e. generating graphical images that capture essential characteristics and highlight interesting relationships. Another approach, which has received far less attention, is to present complex information with sound. This approach, called ``auralization" or ``sonification", is the auditory analog of visualization. Early work in data auralization frequently involved directly mapping some variable in the data to a sound parameter, such as pitch or volume. Multi-variate data could be auralized by mapping several variables to several sound parameters simultaneously. A clear drawback of this approach is the limited practical range of sound parameters that can be presented to human listeners without exceeding their range of perception or comfort. A software auralization system built upon an existing visualization system is briefly described. This system incorporates an aural presentation synchronously and interactively with an animated scientific visualization, so that alternate auralization techniques can be investigated. One such alternate technique involves auditory illusions: sounds which trick the listener into perceiving something other than what is actually being presented. This software system will be used to present an auditory illusion, known for decades among cognitive psychologists, which produces a sound that seems to ascend or descend endlessly in pitch. The applicability of this illusion for presenting Computational Fluid Dynamics data will be demonstrated. CFD data is frequently visualized with thin stream-lines, but thicker stream-ribbons and stream-tubes can also be used, which rotate to convey fluid vorticity. But a purely graphical presentation can yield drawbacks of its own. Thicker stream-tubes can be self-obscuring, and can obscure other scene elements as well, thus motivating a different approach, such as using sound. Naturally

Brain Process for Perception of the “Out of the Body” Tactile Illusion for Virtual Object Interaction

Directory of Open Access Journals (Sweden)

Hye Jin Lee

2015-04-01

Full Text Available “Out of the body” tactile illusion refers to the phenomenon in which one can perceive tactility as if emanating from a location external to the body without any stimulator present there. Taking advantage of such a tactile illusion is one way to provide and realize richer interaction feedback without employing and placing actuators directly at all stimulation target points. However, to further explore its potential, it is important to better understand the underlying physiological and neural mechanism. As such, we measured the brain wave patterns during such tactile illusion and mapped out the corresponding brain activation areas. Participants were given stimulations at different levels with the intention to create veridical (i.e., non-illusory and phantom sensations at different locations along an external hand-held virtual ruler. The experimental data and analysis indicate that both veridical and illusory sensations involve, among others, the parietal lobe, one of the most important components in the tactile information pathway. In addition, we found that as for the illusory sensation, there is an additional processing resulting in the delay for the ERP (event-related potential and involvement by the limbic lobe. These point to regarding illusion as a memory and recognition task as a possible explanation. The present study demonstrated some basic understanding; how humans process “virtual” objects and the way associated tactile illusion is generated will be valuable for HCI (Human-Computer Interaction.

Causality Illusion and Overconfidence in Predicting (QuasiStochastic Financial Events

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Petr Houdek

2017-03-01

Full Text Available We argue that individuals systematically interpret sequences of events in a  causal manner. The aim of this article is to show that people do so even if they are aware of the stochastic nature of the respective sequence. The bias can explain some anomalous behaviour of investors in financial markets. Small as well as professional investors may illusorily perceive causality of former random success and future yield. Laboratory experiments testing the interpretation of stochastically occurring events in financial designs as well as analyses of real trading data from financial markets confirm that investors indeed interpret (quasirandom events casually; they make incorrect predictions and they egocentrically allocate responsibility for their success. The causality illusion induces overconfidence, inefficient investment and risk seeking. In the conclusion, we discuss factors that may limit effects of the causality illusion and suggest future areas for research.

Probing perceptual antinomies with the watercolor illusion and explaining how the brain resolves them.

Science.gov (United States)

Tanca, Maria; Grossberg, Stephen; Pinna, Baingio

2010-01-01

The purpose of this work is to study how the brain solves perceptual antinomies, induced by the watercolor illusion in the color and in the figure-ground segregation domain, when they are present in different parts of the same object. The watercolor illusion shows two main effects: a long-range coloration and an object-hole effect across large enclosed areas (Pinna, 1987, 2005, 2008a, b; Pinna and Grossberg, 2005; Pinna et al., 2001). This illusion strongly enhances the unilateral belongingness of the boundaries (Rubin, 1915) determining grouping and figure-ground segregation more strongly than the well-known Gestalt principles. Due to the watercolor illusion, both the figure and the background assume new properties becoming, respectively, a bulging object and a hole both with a 3-D volumetric appearance (object-hole effect). When the coloration and the object-hole effects induced by the watercolor illusion are opposite (antinomic) within different portions of the same shape, some questions emerge: Do the antinomies split the shape in two parts (a half shape appears as an object and the other half as a hole) or are they solved through a new emergent perceptual result beyond the single effects? Is there a predominance of one component over the other that is less visible or totally invisible? What is perceptible and what is invisible? Is there a wholeness process under conditions where perceptual antinomies coexist? By imparting motion to a watercolored object that gradually should become a hole while overlapping another object placed behind, is the wholeness of the watercolor object weakened or reorganized in a new way? The results of phenomenological experiments suggested that the antinomies tend to be solved through two complement processes of phenomenal wholeness and partialness. These processes are explained in the light of the FACADE neural model of 3-D vision and figure-ground separation (Grossberg, 1994, 2003), notably of how complementary cortical boundary

DISPELLING ILLUSIONS OF REFLECTION: A NEW ANALYSIS OF THE 2007 MAY 19 CORONAL 'WAVE' EVENT

International Nuclear Information System (INIS)

Attrill, Gemma D. R.

2010-01-01

A new analysis of the 2007 May 19 coronal wave-coronal mass ejection-dimmings event is offered employing base difference extreme-ultraviolet (EUV) images. Previous work analyzing the coronal wave associated with this event concluded strongly in favor of purely an MHD wave interpretation for the expanding bright front. This conclusion was based to a significant extent on the identification of multiple reflections of the coronal wave front. The analysis presented here shows that the previously identified 'reflections' are actually optical illusions and result from a misinterpretation of the running difference EUV data. The results of this new multiwavelength analysis indicate that two coronal wave fronts actually developed during the eruption. This new analysis has implications for our understanding of diffuse coronal waves and questions the validity of the analysis and conclusions reached in previous studies.

Can visual illusions be used to facilitate sport skill learning?

NARCIS (Netherlands)

Canal Bruland, R.; van der Meer, Y.; Moerman, J.

2016-01-01

Recently it has been reported that practicing putting with visual illusions that make the hole appear larger than it actually is leads to longer-lasting performance improvements. Interestingly, from a motor control and learning perspective, it may be possible to actually predict the opposite to

Personality correlates of reporting Chinese words from the Deutsch “high-low” word illusion by Chinese-speaking people

Institute of Scientific and Technical Information of China (English)

You Xu; Junpeng Zhu; Wanzhen Chen; Hao Chai; Wei He; Wei Wang

2012-01-01

[Objective] When English-speaking people listen to the Deutseh “high-low” word illusion,they report hearing English words.Whether Chinese-speaking people report Chinese words when listening to the illusion,or whether any reported words might be correlated with personality traits as previous investigations have demonstrated for listening to music in other cultures,is open to question.The present study aimed to address this.[Methods] A total of 308 right-handed,healthy volunteers (177 women and 131 men) were given the illusion test and asked to answer the Zuckerman-Kuhlman personality questionnaire (ZKPQ).Their depressive tendency was measured by the Plutchik-van Praag depression inventory (PVP).[Results] There was no gender effect regarding either the PVP score or the number of reported Chinese words from the illusion.Women scored higher on ZKPQ neuroticism-anxiety than men.The number of meaningful Chinese words reported was correlated with the ZKPQ impulsive sensation-seeking,aggression-hostility,and activity scores.Some words reported by participants who scored higher on these three traits were related in meaning to those scales.[[Conclusion

Mercury Retrograde Effect in Capital Markets: Truth or Illusion?

Directory of Open Access Journals (Sweden)

Murgea Aurora

2016-06-01

Full Text Available From the most ancient times, the astrological beliefs have played an important role in human history, thinking, world-views, language and other elements of social culture. The practice of relating the movement of celestial bodies to events in financial markets is relatively newer but despite the inconsistency between financial astrology and standard economic or financial theory, it seems to be largely spread among capital market traders. This paper evaluates one of the astrological effects on the capital market, more precisely the Mercury retrograde effect on US capital market. Despite the fact that it is just an optical illusion the astrological tradition says that Mercury retrograde periods are characterized by confusion and miscommunications. The trades could be less effective, the individuals more prone to make mistakes so there is a long-held belief that it is better to avoid set plans during Mercury retrograde, signing contracts, starting new ventures or open new stock market positions. The main findings of this study are lower return’s volatilities in the Mercury retrograde periods, inconsistent with the astrologic theories assumptions but consistent with the idea that trader’s beliefs in Mercury retrograde effect could change the market volatility exactly in the opposite sense than the predicted one.

Rubber hand illusion, empathy, and schizotypal experiences in terms of self-other representations.

Science.gov (United States)

Asai, Tomohisa; Mao, Zhu; Sugimori, Eriko; Tanno, Yoshihiko

2011-12-01

When participants observed a rubber hand being touched, their sense of touch was activated (rubber hand illusion: RHI). While this illusion might be caused by multi-modal integration, it may also be related to empathic function, which enables us to simulate the observed information. We examined individual differences in the RHI, including empathic and schizotypal personality traits, as previous research had suggested that schizophrenic patients would be more subject to the RHI. The results indicated that people who experience a stronger RHI might have stronger empathic and schizotypal personalites simultaneously. We discussed these relationships in terms of self-other representations. Copyright © 2011 Elsevier Inc. All rights reserved.

Pareidolias: complex visual illusions in dementia with Lewy bodies.

Science.gov (United States)

Uchiyama, Makoto; Nishio, Yoshiyuki; Yokoi, Kayoko; Hirayama, Kazumi; Imamura, Toru; Shimomura, Tatsuo; Mori, Etsuro

2012-08-01

Patients rarely experience visual hallucinations while being observed by clinicians. Therefore, instruments to detect visual hallucinations directly from patients are needed. Pareidolias, which are complex visual illusions involving ambiguous forms that are perceived as meaningful objects, are analogous to visual hallucinations and have the potential to be a surrogate indicator of visual hallucinations. In this study, we explored the clinical utility of a newly developed instrument for evoking pareidolic illusions, the Pareidolia test, in patients with dementia with Lewy bodies-one of the most common causes of visual hallucinations in the elderly. Thirty-four patients with dementia with Lewy bodies, 34 patients with Alzheimer's disease and 26 healthy controls were given the Pareidolia test. Patients with dementia with Lewy bodies produced a much greater number of pareidolic illusions compared with those with Alzheimer's disease or controls. A receiver operating characteristic analysis demonstrated that the number of pareidolias differentiated dementia with Lewy bodies from Alzheimer's disease with a sensitivity of 100% and a specificity of 88%. Full-length figures and faces of people and animals accounted for >80% of the contents of pareidolias. Pareidolias were observed in patients with dementia with Lewy bodies who had visual hallucinations as well as those who did not have visual hallucinations, suggesting that pareidolias do not reflect visual hallucinations themselves but may reflect susceptibility to visual hallucinations. A sub-analysis of patients with dementia with Lewy bodies who were or were not treated with donepzil demonstrated that the numbers of pareidolias were correlated with visuoperceptual abilities in the former and with indices of hallucinations and delusional misidentifications in the latter. Arousal and attentional deficits mediated by abnormal cholinergic mechanisms and visuoperceptual dysfunctions are likely to contribute to the development

The Binding Ring Illusion: assimilation affects the perceived size of a circular array [v2; ref status: indexed, http://f1000r.es/12q

Directory of Open Access Journals (Sweden)

J Daniel McCarthy

2013-04-01

Full Text Available Our perception of an object’s size arises from the integration of multiple sources of visual information including retinal size, perceived distance and its size relative to other objects in the visual field. This constructive process is revealed through a number of classic size illusions such as the Delboeuf Illusion, the Ebbinghaus Illusion and others illustrating size constancy. Here we present a novel variant of the Delbouef and Ebbinghaus size illusions that we have named the Binding Ring Illusion. The illusion is such that the perceived size of a circular array of elements is underestimated when superimposed by a circular contour – a binding ring – and overestimated when the binding ring slightly exceeds the overall size of the array. Here we characterize the stimulus conditions that lead to the illusion, and the perceptual principles that underlie it. Our findings indicate that the perceived size of an array is susceptible to the assimilation of an explicitly defined superimposed contour. Our results also indicate that the assimilation process takes place at a relatively high level in the visual processing stream, after different spatial frequencies have been integrated and global shape has been constructed. We hypothesize that the Binding Ring Illusion arises due to the fact that the size of an array of elements is not explicitly defined and therefore can be influenced (through a process of assimilation by the presence of a superimposed object that does have an explicit size.

Do you see what I see? A comparative investigation of the Delboeuf illusion in humans (Homo sapiens), rhesus monkeys (Macaca mulatta), and capuchin monkeys (Cebus apella).

Science.gov (United States)

Parrish, Audrey E; Brosnan, Sarah F; Beran, Michael J

2015-10-01

Studying visual illusions is critical to understanding typical visual perception. We investigated whether rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella) perceived the Delboeuf illusion in a similar manner as human adults (Homo sapiens). To test this, in Experiment 1, we presented monkeys and humans with a relative discrimination task that required subjects to choose the larger of 2 central dots that were sometimes encircled by concentric rings. As predicted, humans demonstrated evidence of the Delboeuf illusion, overestimating central dots when small rings surrounded them and underestimating the size of central dots when large rings surrounded them. However, monkeys did not show evidence of the illusion. To rule out an alternate explanation, in Experiment 2, we presented all species with an absolute classification task that required them to classify a central dot as "small" or "large." We presented a range of ring sizes to determine whether the Delboeuf illusion would occur for any dot-to-ring ratios. Here, we found evidence of the Delboeuf illusion in all 3 species. Humans and monkeys underestimated central dot size to a progressively greater degree with progressively larger rings. The Delboeuf illusion now has been extended to include capuchin monkeys and rhesus monkeys, and through such comparative investigations we can better evaluate hypotheses regarding illusion perception among nonhuman animals. (c) 2015 APA, all rights reserved).

Does affective touch influence the virtual reality full body illusion?

NARCIS (Netherlands)

de Jong, Jutta R; Keizer, Anouk; Engel, Manja M; Dijkerman, H Chris

The sense of how we experience our physical body as our own represents a fundamental component of human self-awareness. Body ownership can be studied with bodily illusions which are generated by inducing a visuo-tactile conflict where individuals experience illusionary ownership over a fake body or

The doctrinal illusion of heterogeneity of international law-making processes

NARCIS (Netherlands)

d' Aspremont, J.; Ruiz Fabri, H.; Wofrum, R.; Gogolin, J.

2010-01-01

Contemporary practice shows that the image of international lawmaking as a diverse and heterogeneous process, understood in terms of the multiplicity of the actors involved, is mostly an illusion. Despite strong empirical evidence, many scholars have been lured by this idea or have tried to promote

Athletic footwear: unsafe due to perceptual illusions.

Science.gov (United States)

Robbins, S E; Gouw, G J

1991-02-01

Modern athletic footwear provides remarkable plantar comfort when walking, running, or jumping. However, when injurious plantar loads elicit negligible perceived plantar discomfort, a perceptual illusion is created whereby perceived impact is lower than actual impact, which results in inadequate impact-moderating behavior and consequent injury. The objective of this study was to examine how plantar tactile (mechanical) events affect perceived plantar discomfort. Also, we evaluated the feasibility of a footwear safety standard we propose, which requires elimination of the above illusion. Twenty subjects gave numerical estimates of plantar discomfort produced by simulated locomotion (concurrent vertical (0.1-0.7 kg.cm-2) and horizontal (0.1-0.9 kg.cm-2) plantar loads), with the foot supported by either a smooth rigid surface or a rigid surface with 2 mm high rigid irregularities. Vertical or horizontal load alone evoked no discomfort (P greater than 0.05), whereas together, discomfort emanated from loads as low as 0.4 kg.cm-2. Irregularities heightened discomfort by a factor of 1.89. This suggests that the proposed safety standard is feasible, since compliance could be achieved simply by adding surface irregularities to insoles and by other changes that heighten localized plantar loads. However, until this standard is adhered to, it might be more appropriate to classify athletic footwear as "safety hazards" rather than "protective devices".

A novel upper limb rehabilitation system with self-driven virtual arm illusion.

Science.gov (United States)

Aung, Yee Mon; Al-Jumaily, Adel; Anam, Khairul

2014-01-01

This paper proposes a novel upper extremity rehabilitation system with virtual arm illusion. It aims for fast recovery from lost functions of the upper limb as a result of stroke to provide a novel rehabilitation system for paralyzed patients. The system is integrated with a number of technologies that include Augmented Reality (AR) technology to develop game like exercise, computer vision technology to create the illusion scene, 3D modeling and model simulation, and signal processing to detect user intention via EMG signal. The effectiveness of the developed system has evaluated via usability study and questionnaires which is represented by graphical and analytical methods. The evaluation provides with positive results and this indicates the developed system has potential as an effective rehabilitation system for upper limb impairment.

Illusory object motion in the centre of a radial pattern: The Pursuit–Pursuing illusion

Science.gov (United States)

Ito, Hiroyuki

2012-01-01

A circular object placed in the centre of a radial pattern consisting of thin sectors was found to cause a robust motion illusion. During eye-movement pursuit of a moving target, the presently described stimulus produced illusory background-object motion in the same direction as that of the eye movement. In addition, the display induced illusory stationary perception of a moving object against the whole display motion. In seven experiments, the characteristics of the illusion were examined in terms of luminance relationships and figural characteristics of the radial pattern. Some potential explanations for these findings are discussed. PMID:23145267

Illusory object motion in the centre of a radial pattern: The Pursuit-Pursuing illusion.

Science.gov (United States)

Ito, Hiroyuki

2012-01-01

A circular object placed in the centre of a radial pattern consisting of thin sectors was found to cause a robust motion illusion. During eye-movement pursuit of a moving target, the presently described stimulus produced illusory background-object motion in the same direction as that of the eye movement. In addition, the display induced illusory stationary perception of a moving object against the whole display motion. In seven experiments, the characteristics of the illusion were examined in terms of luminance relationships and figural characteristics of the radial pattern. Some potential explanations for these findings are discussed.

Tüür, Erkki-Sven: Architectonics VI. Passion. Illusion / Guy S. Rickards

Index Scriptorium Estoniae

Rickards, Guy S.

1996-01-01

Uuest heliplaadist "Tüür, Erkki-Sven: Architectonics VI. Passion. Illusion. Crystallisatio. Requiem. Estonian Philharmonic Chamber Choir, Tallinn Chamber Orchestra, Tõnu Kaljuste. ECM New Series 449 459-2 (64 minutes: DDD)

'Robot' Hand Illusion under Delayed Visual Feedback: Relationship between the Senses of Ownership and Agency.

Directory of Open Access Journals (Sweden)

Mohamad Arif Fahmi Ismail

Full Text Available The rubber hand illusion (RHI is an illusion of the self-ownership of a rubber hand that is touched synchronously with one's own hand. While the RHI relates to visual and tactile integration, we can also consider a similar illusion with visual and motor integration on a fake hand. We call this a "robot hand illusion" (RoHI, which relates to both the senses of ownership and agency. Here we investigate the effect of delayed visual feedback on the RoHI. Participants viewed a virtual computer graphic hand controlled by their hand movement recorded using a data glove device. We inserted delays of various lengths between the participant's hand and the virtual hand movements (90-590 ms, and the RoHI effects for each delay condition were systematically tested using a questionnaire. The results showed that the participants felt significantly greater RoHI effects with temporal discrepancies of less than 190 ms compared with longer temporal discrepancies, both in the senses of ownership and agency. Additionally, participants felt significant, but weaker, RoHI effects with temporal discrepancies of 290-490 ms in the sense of agency, but not in the sense of ownership. The participants did not feel a RoHI with temporal discrepancies of 590 ms in either the senses of agency or ownership. Our results suggest that a time window of less than 200 ms is critical for multi-sensory integration processes constituting self-body image.

'Robot' Hand Illusion under Delayed Visual Feedback: Relationship between the Senses of Ownership and Agency.

Science.gov (United States)

Ismail, Mohamad Arif Fahmi; Shimada, Sotaro

2016-01-01

The rubber hand illusion (RHI) is an illusion of the self-ownership of a rubber hand that is touched synchronously with one's own hand. While the RHI relates to visual and tactile integration, we can also consider a similar illusion with visual and motor integration on a fake hand. We call this a "robot hand illusion" (RoHI), which relates to both the senses of ownership and agency. Here we investigate the effect of delayed visual feedback on the RoHI. Participants viewed a virtual computer graphic hand controlled by their hand movement recorded using a data glove device. We inserted delays of various lengths between the participant's hand and the virtual hand movements (90-590 ms), and the RoHI effects for each delay condition were systematically tested using a questionnaire. The results showed that the participants felt significantly greater RoHI effects with temporal discrepancies of less than 190 ms compared with longer temporal discrepancies, both in the senses of ownership and agency. Additionally, participants felt significant, but weaker, RoHI effects with temporal discrepancies of 290-490 ms in the sense of agency, but not in the sense of ownership. The participants did not feel a RoHI with temporal discrepancies of 590 ms in either the senses of agency or ownership. Our results suggest that a time window of less than 200 ms is critical for multi-sensory integration processes constituting self-body image.

Antigravity hills are visual illusions.

Science.gov (United States)

Bressan, Paola; Garlaschelli, Luigi; Barracano, Monica

2003-09-01

Antigravity hills, also known as spook hills or magnetic hills, are natural places where cars put into neutral are seen to move uphill on a slightly sloping road, apparently defying the law of gravity. We show that these effects, popularly attributed to gravitational anomalies, are in fact visual illusions. We re-created all the known types of antigravity spots in our laboratory using tabletop models; the number of visible stretches of road, their slant, and the height of the visible horizon were systematically varied in four experiments. We conclude that antigravity-hill effects follow from a misperception of the eye level relative to gravity, caused by the presence of either contextual inclines or a false horizon line.

Hallucinators find meaning in noises: pareidolic illusions in dementia with Lewy bodies.

Science.gov (United States)

Yokoi, Kayoko; Nishio, Yoshiyuki; Uchiyama, Makoto; Shimomura, Tatsuo; Iizuka, Osamu; Mori, Etsuro

2014-04-01

By definition, visual illusions and hallucinations differ in whether the perceived objects exist in reality. A recent study challenged this dichotomy, in which pareidolias, a type of complex visual illusion involving ambiguous forms being perceived as meaningful objects, are very common and phenomenologically similar to visual hallucinations in dementia with Lewy bodies (DLB). We hypothesise that a common psychological mechanism exists between pareidolias and visual hallucinations in DLB that confers meaning upon meaningless visual information. Furthermore, we believe that these two types of visual misperceptions have a common underlying neural mechanism, namely, cholinergic insufficiency. The current study investigated pareidolic illusions using meaningless visual noise stimuli (the noise pareidolia test) in 34 patients with DLB, 34 patients with Alzheimer׳s disease and 28 healthy controls. Fifteen patients with DLB were administered the noise pareidolia test twice, before and after donepezil treatment. Three major findings were discovered: (1) DLB patients saw meaningful illusory images (pareidolias) in meaningless visual stimuli, (2) the number of pareidolic responses correlated with the severity of visual hallucinations, and (3) cholinergic enhancement reduced both the number of pareidolias and the severity of visual hallucinations in patients with DLB. These findings suggest that a common underlying psychological and neural mechanism exists between pareidolias and visual hallucinations in DLB. Copyright © 2014 Elsevier Ltd. All rights reserved.

Six-month-old infants' perception of the hollow face illusion: evidence for a general convexity bias.

Science.gov (United States)

Corrow, Sherryse L; Mathison, Jordan; Granrud, Carl E; Yonas, Albert

2014-01-01

Corrow, Granrud, Mathison, and Yonas (2011, Perception, 40, 1376-1383) found evidence that 6-month-old infants perceive the hollow face illusion. In the present study we asked whether 6-month-old infants perceive illusory depth reversal for a nonface object and whether infants' perception of the hollow face illusion is affected by mask orientation inversion. In experiment 1 infants viewed a concave bowl, and their reaches were recorded under monocular and binocular viewing conditions. Infants reached to the bowl as if it were convex significantly more often in the monocular than in the binocular viewing condition. These results suggest that infants perceive illusory depth reversal with a nonface stimulus and that the infant visual system has a bias to perceive objects as convex. Infants in experiment 2 viewed a concave face-like mask in upright and inverted orientations. Infants reached to the display as if it were convex more in the monocular than in the binocular condition; however, mask orientation had no effect on reaching. Previous findings that adults' perception of the hollow face illusion is affected by mask orientation inversion have been interpreted as evidence of stored-knowledge influences on perception. However, we found no evidence of such influences in infants, suggesting that their perception of this illusion may not be affected by stored knowledge, and that perceived depth reversal is not face-specific in infants.

Adaptation of postural recovery responses to a vestibular sensory illusion in individuals with Parkinson disease and healthy controls.

Science.gov (United States)

Lester, Mark E; Cavanaugh, James T; Foreman, K Bo; Shaffer, Scott W; Marcus, Robin; Dibble, Leland E

2017-10-01

The ability to adapt postural responses to sensory illusions diminishes with age and is further impaired by Parkinson disease. However, limited information exists regarding training-related adaptions of sensory reweighting in these populations. This study sought to determine whether Parkinson disease or age would differentially affect acute postural recovery or adaptive postural responses to novel or repeated exposure to sensory illusions using galvanic vestibular stimulation during quiet stance. Acutely, individuals with Parkinson disease demonstrated larger center of pressure coefficient of variation compared to controls. Unlike individuals with Parkinson disease and asymptomatic older adults, healthy young adults acutely demonstrated a reduction in Sample Entropy to the sensory illusion. Following a period of consolidation Sample Entropy increased in the healthy young group, which coincided with a decreased center of pressure coefficient of variation. Similar changes were not observed in the Parkinson disease or older adult groups. Taken together, these results suggest that young adults learn to adapt to vestibular illusion in a more robust manner than older adults or those with Parkinson disease. Further investigation into the nature of this adaptive difference is warranted. Published by Elsevier Ltd.

Visual illusion in mass estimation of cut food.

Science.gov (United States)

Wada, Yuji; Tsuzuki, Daisuke; Kobayashi, Naoki; Hayakawa, Fumiyo; Kohyama, Kaoru

2007-07-01

We investigated the effect of the appearance of cut food on visual mass estimation. In this experiment, we manipulated the shape (e.g., a block, fine strips, or small cubes) of food samples of various masses, and presented them on a CRT display as stimuli. Eleven subjects participated in tasks to choose the picture of the food sample which they felt indicated a target mass. We used raw carrots and surimi (ground fish) gel as hard and soft samples, respectively. The results clearly confirm an existence of an illusion, and this indicates that the appearance of food interferes with visual mass estimation. Specifically, participants often overestimated the mass of finely cut food, especially fine strips, whereas they could accurately estimate the mass of block samples, regardless of the physical characteristics of the foods. The overestimation of the mass of cut food increased with the food's actual mass, and was particularly obvious with increases of apparent volume when cut into fine strips. These results suggest that the apparent volume of a food sample effects the visual estimation of its mass. Hence we can conclude that there are illusions associated with the visual presentation of food that may influence various food impressions, including satisfaction and eating behaviour.

Assessment of Positive Illusions of the Physical Attractiveness of Romantic Partners

NARCIS (Netherlands)

Barelds, D.P.H.; Dijkstra, Pieternel; Koudenburg, N.; Swami, V.

2011-01-01

Positive illusions about a partner's physical attractiveness occur when individuals' ratings of their partner's attractiveness are more positive than more objective ratings. Ratings that may serve as a''reality benchmark' include ratings by the partner him/herself and observer ratings. The present

Reports of Wins and Risk Taking : An Investigation of the Mediating Effect of the Illusion of Control.

OpenAIRE

Martinez , Frederic; Le Floch , Valérie; Gaffié , Bernard; Villejoubert , Gaëlle

2011-01-01

International audience; Two experiments examined the relationships between the knowledge that another person has won in a gamble, the illusion of control and risk taking. Participants played a computer-simulated French roulette game individually. Before playing, some participants learnt that another person won a large amount of money. Results from a first experiment (n=24) validated a causal model where the knowledge of another person's win increased the illusion of control, measured with bet...

Bodily pleasure matters: Velocity of touch modulates body ownership during the rubber hand illusion

Directory of Open Access Journals (Sweden)

Laura eCrucianelli

2013-10-01

Full Text Available The sense of body ownership represents a fundamental aspect of our self-consciousness. Influential experimental paradigms, such as the rubber hand illusion (RHI, in which a seen rubber hand is experienced as part of one’s body when one’s own unseen hand receives congruent tactile stimulation, have extensively examined the role of exteroceptive, multisensory integration on body ownership. However, remarkably, despite the more general current interest in the nature and role of interoception in emotion and consciousness, no study has investigated how the illusion may be affected by interoceptive bodily signals, such as affective touch. Here, we recruited 52 healthy, adult participants and we investigated for the first time, whether applying slow velocity, light tactile stimuli, known to elicit interoceptive feelings of pleasantness, would influence the illusion more than faster, emotionally-neutral, tactile stimuli. We also examined whether seeing another person’s hand versus a rubber hand would reduce the illusion in slow versus fast stroking conditions, as interoceptive signals are used to represent one’s own body from within and it is unclear how they would be integrated with visual signals from another person’s hand. We found that slow velocity touch was perceived as more pleasant and it produced higher levels of subjective embodiment during the RHI compared with fast touch. Moreover, this effect applied irrespective of whether the seen hand was a rubber or a confederate’s hand. These findings provide support for the idea that affective touch, and more generally interoception, may have a unique contribution to the sense of body ownership, and by implication to our embodied psychological self.

Ilusões: o olho mágico da percepção Illusions: a window into perception

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Marcus Vinícius C Baldo

2003-12-01

Full Text Available A percepção é a construção ativa de um estado neural que se correlaciona a elementos biologicamente relevantes do ambiente. Esta correlação, longe de estabelecer uma representação fiel do mundo, guia nossas ações na elaboração de comportamentos adaptativos, sendo, portanto, condicionada por fatores evolutivos. Já que a construção de um percepto é um processo intrinsecamente ambíguo, discrepâncias perceptivas podem surgir a partir de condições idênticas de estimulação. Essas discrepâncias são denominadas ilusões, e se originam dos mesmos mecanismos fisiológicos que produzem a nossa percepção cotidiana. Derivando de diferentes fatores, tais como ópticos, sensoriais e cognitivos, as ilusões visuais são instrumentos úteis na exploração das bases fisiológicas da percepção e de sua interação com o planejamento e execução de ações motoras. Aqui, examinamos as origens biológicas das ilusões visuais e algumas de suas relações com aspectos neurobiológicos, filosóficos e estéticos.Perception is the active construction of a neural state that correlates with biologically relevant elements present in the environment. This correlation, far from affording a one-to-one mapping, nonetheless guides our actions towards adaptive behaviors, thus being forged under evolutionary constraints. Since the construction of a percept is an intrinsically ambiguous process, perceptual discrepancies can arise from identical stimulation patterns. The recognition of these discrepancies is termed illusion, which originates, however, from the same physiological mechanisms that ordinarily lead to standard perception. Emanating from different sources, such as optical, sensory and cognitive factors, visual illusions are useful tools in accessing the physiological basis of perceptual processes and their interaction with motor planning and execution. Here we examine the biological roots of visual illusions and their interplay with some

The continuous Wagon Wheel Illusion depends on, but is not identical to neuronal adaptation.

Science.gov (United States)

VanRullen, Rufin

2007-07-01

The occurrence of perceived reversed motion while observers view a continuous, periodically moving stimulus (a bistable phenomenon coined the "continuous Wagon Wheel Illusion" or "c-WWI") has been taken as evidence that some aspects of motion perception rely on discrete sampling of visual information. Alternative accounts rely on the possibility of a motion aftereffect that may become visible even while the adapting stimulus is present. Here I show that motion adaptation might be necessary, but is not sufficient to explain the illusion. When local adaptation is prevented by slowly drifting the moving wheel across the retina, the c-WWI illusion tends to decrease, as do other bistable percepts (e.g. binocular rivalry). However, the strength of the c-WWI and that of adaptation (as measured by either the static or flicker motion aftereffects) are not directly related: although the c-WWI decreases with increasing eccentricity, the aftereffects actually intensify concurrently. A similar dissociation can be induced by manipulating stimulus contrast. This indicates that the c-WWI may be enabled by, but is not equivalent to, local motion adaptation - and that other factors such as discrete sampling may be involved in its generation.

The Flushtration Count Illusion: Attribute substitution tricks our interpretation of a simple visual event sequence.

Science.gov (United States)

Thomas, Cyril; Didierjean, André; Kuhn, Gustav

2018-04-17

When faced with a difficult question, people sometimes work out an answer to a related, easier question without realizing that a substitution has taken place (e.g., Kahneman, 2011, Thinking, fast and slow. New York, Farrar, Strauss, Giroux). In two experiments, we investigated whether this attribute substitution effect can also affect the interpretation of a simple visual event sequence. We used a magic trick called the 'Flushtration Count Illusion', which involves a technique used by magicians to give the illusion of having seen multiple cards with identical backs, when in fact only the back of one card (the bottom card) is repeatedly shown. In Experiment 1, we demonstrated that most participants are susceptible to the illusion, even if they have the visual and analytical reasoning capacity to correctly process the sequence. In Experiment 2, we demonstrated that participants construct a biased and simplified representation of the Flushtration Count by substituting some attributes of the event sequence. We discussed of the psychological processes underlying this attribute substitution effect. © 2018 The British Psychological Society.

Overlapped optics induced perfect coherent effects

Science.gov (United States)

Li, Jian Jie; Zang, Xiao Fei; Mao, Jun Fa; Tang, Min; Zhu, Yi Ming; Zhuang, Song Lin

2013-12-01

For traditional coherent effects, two separated identical point sources can be interfered with each other only when the optical path difference is integer number of wavelengths, leading to alternate dark and bright fringes for different optical path difference. For hundreds of years, such a perfect coherent condition seems insurmountable. However, in this paper, based on transformation optics, two separated in-phase identical point sources can induce perfect interference with each other without satisfying the traditional coherent condition. This shifting illusion media is realized by inductor-capacitor transmission line network. Theoretical analysis, numerical simulations and experimental results are performed to confirm such a kind of perfect coherent effect and it is found that the total radiation power of multiple elements system can be greatly enhanced. Our investigation may be applicable to National Ignition Facility (NIF), Inertial Confined Fusion (ICF) of China, LED lighting technology, terahertz communication, and so on.

Tactile mouse generating velvet hand illusion on human palm

Directory of Open Access Journals (Sweden)

Nadar Rajaei

2016-09-01

Full Text Available To enhance virtual reality (VR generated by tactile displays, we have focused on a novel tactile illusion, called the Velvet Hand Illusion (VHI. In VHI, moving two parallel wires back and forth between the two hands leads humans to perceive a velvet-like surface between their hands. In earlier studies, we revealed that the intensity of VHI could be controlled by a ratio (r/D, where r and D are the wire stroke and wire distance, respectively. According to these findings, we investigate in this study whether a common tactile display is able to produce VHI, and whether the ratio can also control VHI intensity. We prepare a dot-matrix display as a tactile display in which moving one line of the display’s pins is considered as a wire pattern. We investigate the VHI intensity with regard to changing the stroke r and the line distance D using paired comparison. Experimental results show that the VHI intensity is increased or decreased by changing r and D. We conclude that VHI can be created by the tactile display, and the intensity of VHI is controlled by changing the ratio of r/D.

Spreading Optics in the primary school

International Nuclear Information System (INIS)

Gargallo, Ana; Gómez-Varela, Ana I; Gónzalez-Nuñez, Héctor; Delgado, Tamara; Almaguer, Citlalli; Cambronero, Ferran; García-Sánchez, Ángel; Pallarés, David; Aymerich, María; Aragón, Ángel L; Flores-Arias, Maria T

2015-01-01

The USC-OSA is a student chapter located at the University of Santiago de Compostela (Spain) whose objective is to bring optics and photonics knowledge closer to general public. In order to arouse kids' interest in Optics we developed an activity called Funny Light. This activity consisted on a visit of some USC-OSA members to a several local primary schools where we organized several optics experiments. In this work we present the optics demonstrations and the reaction of the 6 years-old students. The activities with greater acceptance include an explanation of light properties as polarization, refraction or reflection, and the workshop where they learnt how to build their own kaleidoscope and made a chromatic disk. Besides, they also participated in a demonstration and explanation of color properties and some optical illusions. We think that this activity has several benefits including spreading Optics through children meanwhile they have fun and experiment science in real life, as well as helping teachers to explain some complex properties and Physics phenomena of light. Given the broad acceptance of this activity, we are intending to make it a routine event of our student chapter repeating it every year. (paper)

Spreading Optics in the primary school

Science.gov (United States)

Gargallo, Ana; Gómez-Varela, Ana I.; Gónzalez-Nuñez, Héctor; Delgado, Tamara; Almaguer, Citlalli; Cambronero, Ferran; García-Sánchez, Ángel; Pallarés, David; Aymerich, María; Aragón, Ángel L.; Flores-Arias, Maria T.

2015-04-01

The USC-OSA is a student chapter located at the University of Santiago de Compostela (Spain) whose objective is to bring optics and photonics knowledge closer to general public. In order to arouse kids' interest in Optics we developed an activity called Funny Light. This activity consisted on a visit of some USC-OSA members to a several local primary schools where we organized several optics experiments. In this work we present the optics demonstrations and the reaction of the 6 years-old students. The activities with greater acceptance include an explanation of light properties as polarization, refraction or reflection, and the workshop where they learnt how to build their own kaleidoscope and made a chromatic disk. Besides, they also participated in a demonstration and explanation of color properties and some optical illusions. We think that this activity has several benefits including spreading Optics through children meanwhile they have fun and experiment science in real life, as well as helping teachers to explain some complex properties and Physics phenomena of light. Given the broad acceptance of this activity, we are intending to make it a routine event of our student chapter repeating it every year.

Stimulus meanings alter illusory self-motion (vection)--experimental examination of the train illusion.

Science.gov (United States)

Seno, Takeharu; Fukuda, Haruaki

2012-01-01

Over the last 100 years, numerous studies have examined the effective visual stimulus properties for inducing illusory self-motion (known as vection). This vection is often experienced more strongly in daily life than under controlled experimental conditions. One well-known example of vection in real life is the so-called 'train illusion'. In the present study, we showed that this train illusion can also be generated in the laboratory using virtual computer graphics-based motion stimuli. We also demonstrated that this vection can be modified by altering the meaning of the visual stimuli (i.e., top down effects). Importantly, we show that the semantic meaning of a stimulus can inhibit or facilitate vection, even when there is no physical change to the stimulus.

Body ownership and experiential ownership in the self-touching illusion

Directory of Open Access Journals (Sweden)

Caleb eLiang

2015-01-01

Full Text Available We investigate two issues about the subjective experience of one’s body: first, is the experience of owning a full-body fundamentally different from the experience of owning a body-part? Second, when I experience a bodily sensation, does it guarantee that I cannot be wrong about whether it is me who feels it? To address these issues, we conducted a series of experiments that combined the rubber hand illusion (RHI and the body swap illusion. The subject wore a head mounted display (HMD connected with a stereo camera set on the experimenter’s head. Sitting face to face, they used their right hand holding a paintbrush to brush each other’s left hand. Through the HMD, the subject adopted the experimenter’s first-person perspective (1PP as if it was his/her own 1PP: the subject watched either the experimenter’s hand from the adopted 1PP, and/or the subject’s own hand from the adopted third-person perspective (3PP in the opposite direction (180°, or the subject’s full body from the adopted 3PP (180°, with or without face. The synchronous full-body conditions generate a self-touching illusion: many participants felt that I was brushing my own hand! We found that (1 the sense of body-part ownership and the sense of full-body ownership are not fundamentally different from each other; and (2 our data present a strong case against the mainstream philosophical view called the immunity principle (IEM. We argue that it is possible for misrepresentation to occur in the subject’s sense of experiential ownership (the sense that I am the one who is having this bodily experience. We discuss these findings and conclude that not only the sense of body ownership but also the sense of experiential ownership call for further interdisciplinary studies.

On an illusion of superluminal velocities produced by gravitational lenses

International Nuclear Information System (INIS)

Ingel, L.Kh.

1981-01-01

It is noted that gravitational lenses, by focusing the radiation of an object, increase the angle which it subtends. This in turn produces the illusion of an increase in velocities at right angles to the line of sight. Preliminary estimates are made which indicate a rather high probability of strong distortion of the observed velocities

Visual Spatial Disorientation: Re-Visiting the Black Hole Illusion

Science.gov (United States)

2007-01-24

National Transportation Safety Board. Controlled Flight into Terrain, Korean Air Flight 801 , Nimitz Hill, Guam; 1997. 50. National Transportation Safety...According to a Boeing study of worldwide commercial airline accidents, the approach and landing phase of flying, although only accounting for 4% of the...VISUAL SPATIAL DISORIENTATION Kraft (31) described four night visual, landing airline accidents. Black Hole Illusion 5 1. In 1965, a United Airlines

An illusion of control modulates the reluctance to tempt fate

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Chloe L. Swirsky

2011-10-01

Full Text Available The tempting fate effect is that the probability of a fateful outcome is deemed higher following an action that ``tempts'' the outcome than in the absence of such an action. In this paper we evaluate the hypothesis that the effect is due to an illusion of control induced by a causal framing of the situation. Causal frames require that the action make a difference to an outcome and that the action precedes the outcome. If an illusion of control modulates the reluctance to tempt fate, then actions that make a difference to well-being and that occur prior to the outcome should tempt fate most strongly. In Experiments 1--3 we varied whether the action makes a difference and the temporal order of action and outcome. In Experiment 4 we tested whether an action can tempt fate if all outcomes are negative. The results of all four experiments supported our hypothesis that the tempting fate effect depends on a causal construal that gives rise to a false sense of control.

Testing day: The effects of processing bias induced by Navon stimuli on the strength of the Müller-Lyer illusion.

Science.gov (United States)

Mundy, Matthew E

2014-01-01

Explanations for the cognitive basis of the Müller-Lyer illusion are still frustratingly mixed. To date, Day's (1989) theory of perceptual compromise has received little empirical attention. In this study, we examine the merit of Day's hypothesis for the Müller-Lyer illusion by biasing participants toward global or local visual processing through exposure to Navon (1977) stimuli, which are known to alter processing level preference for a short time. Participants (N = 306) were randomly allocated to global, local, or control conditions. Those in global or local conditions were exposed to Navon stimuli for 5 min and participants were required to report on the global or local stimulus features, respectively. Subsequently, participants completed a computerized Müller-Lyer experiment where they adjusted the length of a line to match an illusory-figure. The illusion was significantly stronger for participants with a global bias, and significantly weaker for those with a local bias, compared with the control condition. These findings provide empirical support for Day's "conflicting cues" theory of perceptual compromise in the Müller-Lyer illusion.

Sliding perspectives: dissociating ownership from self-location during full body illusions in virtual reality.

Science.gov (United States)

Maselli, Antonella; Slater, Mel

2014-01-01

Bodily illusions have been used to study bodily self-consciousness and disentangle its various components, among other the sense of ownership and self-location. Congruent multimodal correlations between the real body and a fake humanoid body can in fact trigger the illusion that the fake body is one's own and/or disrupt the unity between the perceived self-location and the position of the physical body. However, the extent to which changes in self-location entail changes in ownership is still matter of debate. Here we address this problem with the support of immersive virtual reality. Congruent visuotactile stimulation was delivered on healthy participants to trigger full body illusions from different visual perspectives, each resulting in a different degree of overlap between real and virtual body. Changes in ownership and self-location were measured with novel self-posture assessment tasks and with an adapted version of the cross-modal congruency task. We found that, despite their strong coupling, self-location and ownership can be selectively altered: self-location was affected when having a third person perspective over the virtual body, while ownership toward the virtual body was experienced only in the conditions with total or partial overlap. Thus, when the virtual body is seen in the far extra-personal space, changes in self-location were not coupled with changes in ownership. If a partial spatial overlap is present, ownership was instead typically experienced with a boosted change in the perceived self-location. We discussed results in the context of the current knowledge of the multisensory integration mechanisms contributing to self-body perception. We argue that changes in the perceived self-location are associated to the dynamical representation of peripersonal space encoded by visuotactile neurons. On the other hand, our results speak in favor of visuo-proprioceptive neuronal populations being a driving trigger in full body ownership illusions.

Sliding perspectives: dissociating ownership from self-location during full body illusions in virtual reality

Science.gov (United States)

Maselli, Antonella; Slater, Mel

2014-01-01

Bodily illusions have been used to study bodily self-consciousness and disentangle its various components, among other the sense of ownership and self-location. Congruent multimodal correlations between the real body and a fake humanoid body can in fact trigger the illusion that the fake body is one's own and/or disrupt the unity between the perceived self-location and the position of the physical body. However, the extent to which changes in self-location entail changes in ownership is still matter of debate. Here we address this problem with the support of immersive virtual reality. Congruent visuotactile stimulation was delivered on healthy participants to trigger full body illusions from different visual perspectives, each resulting in a different degree of overlap between real and virtual body. Changes in ownership and self-location were measured with novel self-posture assessment tasks and with an adapted version of the cross-modal congruency task. We found that, despite their strong coupling, self-location and ownership can be selectively altered: self-location was affected when having a third person perspective over the virtual body, while ownership toward the virtual body was experienced only in the conditions with total or partial overlap. Thus, when the virtual body is seen in the far extra-personal space, changes in self-location were not coupled with changes in ownership. If a partial spatial overlap is present, ownership was instead typically experienced with a boosted change in the perceived self-location. We discussed results in the context of the current knowledge of the multisensory integration mechanisms contributing to self-body perception. We argue that changes in the perceived self-location are associated to the dynamical representation of peripersonal space encoded by visuotactile neurons. On the other hand, our results speak in favor of visuo-proprioceptive neuronal populations being a driving trigger in full body ownership illusions. PMID

Ilusi Optis dalam Dunia Seni dan Desain

Directory of Open Access Journals (Sweden)

Jonata Witabora

2012-10-01

Full Text Available Visual is everything to do with vision. The ability of our brain to interpret visual is what we call visual perception. In the development of art and design, many artists and designers study visual perception and embody it in their works. One part of visual perception which attracts artists and made as the base on their work is optical illusion. This, in turn creates new streams in the world of art and design. Optical illusion is an anomaly in visual perception, a deceiving experience occurs beyond the control of the observer. Article maps out what optical illusions is, and identify a variety of optical illusions and their application in art and design. 

Real-time decreased sensitivity to an audio-visual illusion during goal-directed reaching.

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Luc Tremblay

Full Text Available In humans, sensory afferences are combined and integrated by the central nervous system (Ernst MO, Bülthoff HH (2004 Trends Cogn. Sci. 8: 162-169 and appear to provide a holistic representation of the environment. Empirical studies have repeatedly shown that vision dominates the other senses, especially for tasks with spatial demands. In contrast, it has also been observed that sound can strongly alter the perception of visual events. For example, when presented with 2 flashes and 1 beep in a very brief period of time, humans often report seeing 1 flash (i.e. fusion illusion, Andersen TS, Tiippana K, Sams M (2004 Brain Res. Cogn. Brain Res. 21: 301-308. However, it is not known how an unfolding movement modulates the contribution of vision to perception. Here, we used the audio-visual illusion to demonstrate that goal-directed movements can alter visual information processing in real-time. Specifically, the fusion illusion was linearly reduced as a function of limb velocity. These results suggest that cue combination and integration can be modulated in real-time by goal-directed behaviors; perhaps through sensory gating (Chapman CE, Beauchamp E (2006 J. Neurophysiol. 96: 1664-1675 and/or altered sensory noise (Ernst MO, Bülthoff HH (2004 Trends Cogn. Sci. 8: 162-169 during limb movements.

Reduction of the elevator illusion from continued hypergravity exposure and visual error-corrective feedback

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Welch, R. B.; Cohen, M. M.; DeRoshia, C. W.

1996-01-01

Ten subjects served as their own controls in two conditions of continuous, centrifugally produced hypergravity (+2 Gz) and a 1-G control condition. Before and after exposure, open-loop measures were obtained of (1) motor control, (2) visual localization, and (3) hand-eye coordination. During exposure in the visual feedback/hypergravity condition, subjects received terminal visual error-corrective feedback from their target pointing, and in the no-visual feedback/hypergravity condition they pointed open loop. As expected, the motor control measures for both experimental conditions revealed very short lived underreaching (the muscle-loading effect) at the outset of hypergravity and an equally transient negative aftereffect on returning to 1 G. The substantial (approximately 17 degrees) initial elevator illusion experienced in both hypergravity conditions declined over the course of the exposure period, whether or not visual feedback was provided. This effect was tentatively attributed to habituation of the otoliths. Visual feedback produced a smaller additional decrement and a postexposure negative after-effect, possible evidence for visual recalibration. Surprisingly, the target-pointing error made during hypergravity in the no-visual-feedback condition was substantially less than that predicted by subjects' elevator illusion. This finding calls into question the neural outflow model as a complete explanation of this illusion.

Normal temporal binding window but no sound-induced flash illusion in people with one eye.

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Moro, Stefania S; Steeves, Jennifer K E

2018-04-19

Integrating vision and hearing is an important way in which we process our rich sensory environment. Partial deprivation of the visual system from the loss of one eye early in life results in adaptive changes in the remaining senses (e.g., Hoover et al. in Exp Brain Res 216:565-74, 2012). The current study investigates whether losing one eye early in life impacts the temporal window in which audiovisual events are integrated and whether there is vulnerability to the sound-induced flash illusion. In Experiment 1, we measured the temporal binding window with a simultaneity judgement task where low-level auditory and visual stimuli were presented at different stimulus onset asynchronies. People with one eye did not differ in the width of their temporal binding window, but they took longer to make judgements compared to binocular viewing controls. In Experiment 2, we measured how many light flashes were perceived when a single flash was paired with multiple auditory beeps in close succession (sound induced flash illusion). Unlike controls, who perceived multiple light flashes with two, three or four beeps, people with one eye were not susceptible to the sound-induced flash illusion. In addition, they took no longer to respond compared to both binocular and monocular (eye-patched) viewing controls. Taken together, these results suggest that the lack of susceptibility to the sound-induced flash illusion in people with one eye cannot be accounted for by the width of the temporal binding window. These results provide evidence for adaptations in audiovisual integration due to the reduction of visual input from the loss of one eye early in life.

The Silhouette Zoetrope: A New Blend of Motion, Mirroring, Depth, and Size Illusions.

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Veras, Christine; Pham, Quang-Cuong; Maus, Gerrit W

2017-01-01

Here, we report a novel combination of visual illusions in one stimulus device, a contemporary innovation of the traditional zoetrope, called Silhouette Zoetrope. In this new device, an animation of moving silhouettes is created by sequential cutouts placed outside a rotating empty cylinder, with slits illuminating the cutouts successively from the back. This "inside-out" zoetrope incurs the following visual effects: the resulting animated figures are perceived (a) horizontally flipped, (b) inside the cylinder, and (c) appear to be of different size than the actual cutout object. Here, we explore the unique combination of illusions in this new device. We demonstrate how the geometry of the device leads to a retinal image consistent with a mirrored and distorted image and binocular disparities consistent with the perception of an object inside the cylinder.

Ego depletion and positive illusions: does the construction of positivity require regulatory resources?

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Fischer, Peter; Greitemeyer, Tobias; Frey, Dieter

2007-09-01

Individuals frequently exhibit positive illusions about their own abilities, their possibilities to control their environment, and future expectations. The authors propose that positive illusions require resources of self-control, which is considered to be a limited resource similar to energy or strength. Five studies revealed that people with depleted self-regulatory resources indeed exhibited a less-optimistic sense of their own abilities (Study 1), a lower sense of subjective control (Study 2), and less-optimistic expectations about their future (Study 3). Two further studies shed light on the underlying psychological process: Ego-depleted (compared to nondepleted) individuals generated/retrieved less positive self-relevant attributes (Studies 4 and 5) and reported a lower sense of general self-efficacy (Study 5), which both partially mediated the impact of ego depletion on positive self-views (Study 5).

Light Refraction by Water as a Rationale for the Poggendorff Illusion

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Bozhevolnyi, Sergey I.

2017-01-01

The Poggendorff illusion in its classical form of parallel lines interrupting a transversal is viewed from the perspective of being related to the everyday experience of observing the light refraction in water. It is argued that if one considers a transversal to be a light ray in air and the para...

Dynamics of the G-excess illusion

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Baylor, K. A.; Reschke, M.; Guedry, F. E.; Mcgrath, B. J.; Rupert, A. H.

1992-01-01

The G-excess illusion is increasingly recognized as a cause of aviation mishaps especially when pilots perform high-speed, steeply banked turns at low altitudes. Centrifuge studies of this illusion have examined the perception of subject orientation and/or target displacement during maintained hypergravity with the subject's head held stationary. The transient illusory perceptions produced by moving the head in hypergravity are difficult to study onboard centrifuges because the high angular velocity ensures the presence of strong Coriolis cross-coupled semicircular canal effects that mask immediate transient otolith-organ effects. The present study reports perceptions following head movements in hypergravity produced by high-speed aircraft maintaining a banked attitude with low angular velocity to minimize cross-coupled effects. Methods: Fourteen subjects flew on the NASA KC-135 and were exposed to resultant gravity forces of 1.3, 1.5, and 1.8 G for 3 minute periods. On command, seated subjects made controlled head movements in roll, pitch, and yaw at 30 second intervals both in the dark and with faint targets at a distance of 5 feet. Results: head movement produced transient perception of target displacement and velocity at levels as low as 1.3 G. Reports of target velocity without appropriate corresponding displacement were common. At 1.8 G when yaw head movements were made from a face down position, 4 subjects reported oscillatory rotational target displacement with fast and slow alternating components suggestive of torsional nystagmus. Head movements evoked symptoms of nausea in most subjects, with 2 subjects and 1 observer vomiting. Conclusions: The transient percepts present conflicting signals, which introduced confusion in target and subject orientation. Repeated head movements in hypergravity generate nausea by mechanisms distinct from cross-coupled Coriolis effects.

Trend of Average Wages as Indicator of Hypothetical Money Illusion

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Julian Daszkowski

2010-06-01

Full Text Available The definition of wage in Poland not before 1998 includes any value of social security contribution. Changed definition creates higher level of reported wages, but was expected not to influence the take home pay. Nevertheless, the trend of average wages, after a short period, has returned to its previous line. Such effect is explained in the term of money illusion.

The Rubber Hand Illusion Revisited: Visuotactile Integration and Self-Attribution

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Tsakiris, Manos; Haggard, Patrick

2005-01-01

Watching a rubber hand being stroked, while one's own unseen hand is synchronously stroked, may cause the rubber hand to be attributed to one's own body, to "feel like it's my hand." A behavioral measure of the rubber hand illusion (RHI) is a drift of the perceived position of one's own hand toward the rubber hand. The authors investigated (a) the…

Eye movement instructions modulate motion illusion and body sway with Op Art.

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Kapoula, Zoï; Lang, Alexandre; Vernet, Marine; Locher, Paul

2015-01-01

Op Art generates illusory visual motion. It has been proposed that eye movements participate in such illusion. This study examined the effect of eye movement instructions (fixation vs. free exploration) on the sensation of motion as well as the body sway of subjects viewing Op Art paintings. Twenty-eight healthy adults in orthostatic stance were successively exposed to three visual stimuli consisting of one figure representing a cross (baseline condition) and two Op Art paintings providing sense of motion in depth-Bridget Riley's Movements in Squares and Akiyoshi Kitaoka's Rollers. Before their exposure to the Op Art images, participants were instructed either to fixate at the center of the image (fixation condition) or to explore the artwork (free viewing condition). Posture was measured for 30 s per condition using a body fixed sensor (accelerometer). The major finding of this study is that the two Op Art paintings induced a larger antero-posterior body sway both in terms of speed and displacement and an increased motion illusion in the free viewing condition as compared to the fixation condition. For body sway, this effect was significant for the Riley painting, while for motion illusion this effect was significant for Kitaoka's image. These results are attributed to macro-saccades presumably occurring under free viewing instructions, and most likely to the small vergence drifts during fixations following the saccades; such movements in interaction with visual properties of each image would increase either the illusory motion sensation or the antero-posterior body sway.

Brain Regions Associated to a Kinesthetic Illusion Evoked by Watching a Video of One's Own Moving Hand.

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Kaneko, Fuminari; Blanchard, Caroline; Lebar, Nicolas; Nazarian, Bruno; Kavounoudias, Anne; Romaiguère, Patricia

2015-01-01

It is well known that kinesthetic illusions can be induced by stimulation of several sensory systems (proprioception, touch, vision…). In this study we investigated the cerebral network underlying a kinesthetic illusion induced by visual stimulation by using functional magnetic resonance imaging (fMRI) in humans. Participants were instructed to keep their hand still while watching the video of their own moving hand (Self Hand) or that of someone else's moving hand (Other Hand). In the Self Hand condition they experienced an illusory sensation that their hand was moving whereas the Other Hand condition did not induce any kinesthetic illusion. The contrast between the Self Hand and Other Hand conditions showed significant activation in the left dorsal and ventral premotor cortices, in the left Superior and Inferior Parietal lobules, at the right Occipito-Temporal junction as well as in bilateral Insula and Putamen. Most strikingly, there was no activation in the primary motor and somatosensory cortices, whilst previous studies have reported significant activation in these regions for vibration-induced kinesthetic illusions. To our knowledge, this is the first study that indicates that humans can experience kinesthetic perception without activation in the primary motor and somatosensory areas. We conclude that under some conditions watching a video of one's own moving hand could lead to activation of a network that is usually involved in processing copies of efference, thus leading to the illusory perception that the real hand is indeed moving.

Brain Regions Associated to a Kinesthetic Illusion Evoked by Watching a Video of One's Own Moving Hand.

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Fuminari Kaneko

Full Text Available It is well known that kinesthetic illusions can be induced by stimulation of several sensory systems (proprioception, touch, vision…. In this study we investigated the cerebral network underlying a kinesthetic illusion induced by visual stimulation by using functional magnetic resonance imaging (fMRI in humans. Participants were instructed to keep their hand still while watching the video of their own moving hand (Self Hand or that of someone else's moving hand (Other Hand. In the Self Hand condition they experienced an illusory sensation that their hand was moving whereas the Other Hand condition did not induce any kinesthetic illusion. The contrast between the Self Hand and Other Hand conditions showed significant activation in the left dorsal and ventral premotor cortices, in the left Superior and Inferior Parietal lobules, at the right Occipito-Temporal junction as well as in bilateral Insula and Putamen. Most strikingly, there was no activation in the primary motor and somatosensory cortices, whilst previous studies have reported significant activation in these regions for vibration-induced kinesthetic illusions. To our knowledge, this is the first study that indicates that humans can experience kinesthetic perception without activation in the primary motor and somatosensory areas. We conclude that under some conditions watching a video of one's own moving hand could lead to activation of a network that is usually involved in processing copies of efference, thus leading to the illusory perception that the real hand is indeed moving.

The Viewing-from-Above Bias and the Silhouette Illusion

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Nikolaus F Troje

2010-12-01

Full Text Available The silhouette illusion published online a number of years ago by the Japanese Flash designer Nobuyuki Kayahara has received substantial attention from the online community. One feature that seems to make it interesting is an apparent rotational bias: Observers see it spinning more often clockwise than counter-clockwise. Here, we show that this rotational bias is in fact due to the visual system's preference for viewpoints from above rather than from below.

High working memory load leads to more Ebbinghaus illusion

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De Fockert, J. W.; Wu, Si

2009-01-01

The evidence that distractor processing increases with greater load on working memory has come mainly from Stroop-type interference tasks, making it difficult to establish whether cognitive load affects distractor processing at the perceptual level or during response selection. We measured the Ebbinghaus illusion under varying levels of working memory load to test whether cognitive control is also relevant for preventing processing of distractors that do not produce any response conflict, and...

Hearing visuo-tactile synchrony - Sound-induced proprioceptive drift in the invisible hand illusion.

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Darnai, Gergely; Szolcsányi, Tibor; Hegedüs, Gábor; Kincses, Péter; Kállai, János; Kovács, Márton; Simon, Eszter; Nagy, Zsófia; Janszky, József

2017-02-01

The rubber hand illusion (RHI) and its variant the invisible hand illusion (IHI) are useful for investigating multisensory aspects of bodily self-consciousness. Here, we explored whether auditory conditioning during an RHI could enhance the trisensory visuo-tactile-proprioceptive interaction underlying the IHI. Our paradigm comprised of an IHI session that was followed by an RHI session and another IHI session. The IHI sessions had two parts presented in counterbalanced order. One part was conducted in silence, whereas the other part was conducted on the backdrop of metronome beats that occurred in synchrony with the brush movements used for the induction of the illusion. In a first experiment, the RHI session also involved metronome beats and was aimed at creating an associative memory between the brush stroking of a rubber hand and the sounds. An analysis of IHI sessions showed that the participants' perceived hand position drifted more towards the body-midline in the metronome relative to the silent condition without any sound-related session differences. Thus, the sounds, but not the auditory RHI conditioning, influenced the IHI. In a second experiment, the RHI session was conducted without metronome beats. This confirmed the conditioning-independent presence of sound-induced proprioceptive drift in the IHI. Together, these findings show that the influence of visuo-tactile integration on proprioceptive updating is modifiable by irrelevant auditory cues merely through the temporal correspondence between the visuo-tactile and auditory events. © 2016 The British Psychological Society.

Effect of slow, small movement on the vibration-evoked kinesthetic illusion.

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Cordo, P J; Gurfinkel, V S; Brumagne, S; Flores-Vieira, C

2005-12-01

The study reported in this paper investigated how vibration-evoked illusions of joint rotation are influenced by slow (0.3 degrees /s), small (2-4 degrees ) passive rotation of the joint. Normal human adults (n=15) matched the perceived position of the left ("reference") arm with the right ("matching") arm while vibration (50 pps, 0.5 mm) was applied for 30 s to the relaxed triceps brachii of the reference arm. Both arms were constrained to rotate horizontally at the elbow. Three experimental conditions were investigated: (1) vibration of the stationary reference arm, (2) slow, small passive extension or flexion of the reference arm during vibration, and (3) slow, small passive extension or flexion of the reference arm without vibration. Triceps brachii vibration at 50 pps induced an illusion of elbow flexion. The movement illusion began after several seconds, relatively fast to begin with and gradually slowing down to a stop. On average, triceps vibration produced illusory motion at an average latency of 6.3 s, amplitude of 9.7 degrees , velocity of 0.6 degrees /s, and duration of 16.4 s. During vibration, slow, small ( approximately 0.3 degrees /s, 1.3 degrees ) passive rotations of the joint dramatically enhanced, stopped, or reversed the direction of illusory movement, depending on the direction of the passive joint rotation. However, the subjects' perceptions of these passive elbow rotations were exaggerated: 2-3 times the size of the actual movement. In the absence of vibration, the subjects accurately reproduced these passive joint rotations. We discuss whether the exaggerated perception of slow, small movement during vibration is better explained by contributions of non muscle spindle Ia afferents or by changes in the mechanical transmission of vibration to the receptor.

Hot or Not: The Role of Instructor Quality and Gender on the Formation of Positive Illusions among Students Using RateMyProfessors.com

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Katherine C. Theyson

2015-02-01

Full Text Available Existing literature indicates that physical attractiveness positively affects variables such as income, perceived employee quality and performance evaluations. Similarly, in the academic arena, studies indicate instructors who are better looking receive better teaching evaluations from their students. Previous analysis of the website RateMyProfessors.com confirms this, indicating that instructors who are viewed by students as - hot- receive higher - quality- ratings than those who are - not.- However, psychology literature indicates that perceptions of attractiveness are influenced by positive illusions, a property whereby individuals with higher quality relationships view each other more positively than objective observers. This paper uses data from Rate My Professors to investigate the existence of positive illusions in the instructor-student relationship. It finds that positive illusions exist, suggesting that existing literature overestimates the premium associated with physical attractiveness. Furthermore, the source of these illusions varies significantly between male and female instructors with important implications for the role of gender in workplace evaluations, hiring, promotion, and tenure.

On the role of spatial phase and phase correlation in vision, illusion, and cognition.

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Gladilin, Evgeny; Eils, Roland

2015-01-01

Numerous findings indicate that spatial phase bears an important cognitive information. Distortion of phase affects topology of edge structures and makes images unrecognizable. In turn, appropriately phase-structured patterns give rise to various illusions of virtual image content and apparent motion. Despite a large body of phenomenological evidence not much is known yet about the role of phase information in neural mechanisms of visual perception and cognition. Here, we are concerned with analysis of the role of spatial phase in computational and biological vision, emergence of visual illusions and pattern recognition. We hypothesize that fundamental importance of phase information for invariant retrieval of structural image features and motion detection promoted development of phase-based mechanisms of neural image processing in course of evolution of biological vision. Using an extension of Fourier phase correlation technique, we show that the core functions of visual system such as motion detection and pattern recognition can be facilitated by the same basic mechanism. Our analysis suggests that emergence of visual illusions can be attributed to presence of coherently phase-shifted repetitive patterns as well as the effects of acuity compensation by saccadic eye movements. We speculate that biological vision relies on perceptual mechanisms effectively similar to phase correlation, and predict neural features of visual pattern (dis)similarity that can be used for experimental validation of our hypothesis of "cognition by phase correlation."

On the role of spatial phase and phase correlation in vision, illusion and cognition

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Evgeny eGladilin

2015-04-01

Full Text Available Numerous findings indicate that spatial phase bears an important cognitive information. Distortion of phase affects topology of edge structures and makes images unrecognizable. In turn, appropriately phase-structured patterns give rise to various illusions of virtual image content and apparent motion. Despite a large body of phenomenological evidence not much is known yet about the role of phase information in neural mechanisms of visual perception and cognition. Here, we are concerned with analysis of the role of spatial phase in computational and biological vision, emergence of visual illusions and pattern recognition. We hypothesize that fundamental importance of phase information for invariant retrieval of structural image features and motion detection promoted development of phase-based mechanisms of neural image processing in course of evolution of biological vision. Using an extension of Fourier phase correlation technique, we show that the core functions of visual system such as motion detection and pattern recognition can be facilitated by the same basic mechanism. Our analysis suggests that emergence of visual illusions can be attributed to presence of coherently phase-shifted repetitive patterns as well as the effects of acuity compensation by saccadic eye movements. We speculate that biological vision relies on perceptual mechanisms effectively similar to phase correlation, and predict neural features of visual pattern (dissimilarity that can be used for experimental validation of our hypothesis of 'cognition by phase correlation'.

Susceptibility to the rubber hand illusion does not tell the whole body-awareness story.

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David, Nicole; Fiori, Francesca; Aglioti, Salvatore M

2014-03-01

The rubber hand illusion (RHI) is an enigmatic illusion that creates a feeling of owning an artificial limb. Enthusiasts of this paradigm assert that it operationalizes bodily self-awareness, but there are reasons to doubt such a clear link. Because little is known about other functional contributions to the RHI, including effects of context-dependent visual processing and cognitive control or the ability to resolve intermodal conflict, we carried out two complementary experiments. In the first, we examined the relationships between the RHI and (1) body awareness, as assessed by the Body Perception Questionnaire (BPQ); (2) context-dependent visual processing, as assessed by the rod-and-frame test (RFT); and (3) conflict resolution, as assessed by the Stroop test. We found a significant positive correlation between the RHI-associated proprioceptive drift and context-dependent visual processing on the RFT, but not between the RHI and body awareness on the BPQ. In the second experiment, we examined the RHI in advanced yoga practitioners with an embodied lifestyle and a heightened sense of their own body in space. They succumbed to the illusion just as much as did yoga-naïve control participants, despite significantly greater body awareness on the BPQ. These findings suggest that susceptibility to the RHI and awareness of one's own body are at least partially independent processes.

Effects of vibratory stimulation-induced kinesthetic illusions on the neural activities of patients with stroke.

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Kodama, Takayuki; Nakano, Hideki; Ohsugi, Hironori; Murata, Shin

2016-01-01

[Purpose] This study evaluated the influence of vibratory stimulation-induced kinesthetic illusion on brain function after stroke. [Subjects] Twelve healthy individuals and 13 stroke patients without motor or sensory loss participated. [Methods] Electroencephalograms were taken at rest and during vibratory stimulation. As a neurophysiological index of brain function, we measured the μ-rhythm, which is present mainly in the kinesthetic cortex and is attenuated by movement or motor imagery and compared the data using source localization analyses in the Standardized Low Resolution Brain Electromagnetic Tomography (sLORETA) program. [Results] At rest, μ-rhythms appeared in the sensorimotor and supplementary motor cortices in both healthy controls and stroke patients. Under vibratory stimulation, no μ-rhythm appeared in the sensorimotor cortex of either group. Moreover, in the supplementary motor area, which stores the motor imagery required for kinesthetic illusions, the μ-rhythms of patients were significantly stronger than those of the controls, although the μ-rhythms of both groups were reduced. Thus, differences in neural activity in the supplementary motor area were apparent between the subject groups. [Conclusion] Kinesthetic illusions do occur in patients with motor deficits due to stroke. The neural basis of the supplementary motor area in stroke patients may be functionally different from that found in healthy controls.

Auditory evoked responses to binaural beat illusion: stimulus generation and the derivation of the Binaural Interaction Component (BIC).

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Ozdamar, Ozcan; Bohorquez, Jorge; Mihajloski, Todor; Yavuz, Erdem; Lachowska, Magdalena

2011-01-01

Electrophysiological indices of auditory binaural beats illusions are studied using late latency evoked responses. Binaural beats are generated by continuous monaural FM tones with slightly different ascending and descending frequencies lasting about 25 ms presented at 1 sec intervals. Frequency changes are carefully adjusted to avoid any creation of abrupt waveform changes. Binaural Interaction Component (BIC) analysis is used to separate the neural responses due to binaural involvement. The results show that the transient auditory evoked responses can be obtained from the auditory illusion of binaural beats.

Modeling and simulation the computer science of illusion

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Raczynski, Stanislaw

2006-01-01

Simulation is the art of using tools - physical or conceptual models, or computer hardware and software, to attempt to create the illusion of reality. The discipline has in recent years expanded to include the modelling of systems that rely on human factors and therefore possess a large proportion of uncertainty, such as social, economic or commercial systems. These new applications make the discipline of modelling and simulation a field of dynamic growth and new research. Stanislaw Raczynski outlines the considerable and promising research that is being conducted to counter the problems of

Veblen effect, marginal utility of money, and money illusion

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Malakhov, Sergey

2013-01-01

The paper discovers microeconomic mechanism of Veblen effect as well as of Giffen case as results of the negative marginal utility of money. The marginal utility of consumption also becomes negative. The total consumption-leisure utility is increased due to the increase in leisure time. This overall effect results in the phenomenon of money illusion on the macroeconomic level. This general effect has deep historical and institutional grounds and, in order to minimize its disequilibrium econom...

The invisible hand illusion: multisensory integration leads to the embodiment of a discrete volume of empty space.

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Guterstam, Arvid; Gentile, Giovanni; Ehrsson, H Henrik

2013-07-01

The dynamic integration of signals from different sensory modalities plays a key role in bodily self-perception. When visual information is used in the multisensory process of localizing and identifying one's own limbs, the sight of a body part often plays a dominant role. For example, it has repeatedly been shown that a viewed object must resemble a humanoid body part to permit illusory self-attribution of that object. Here, we report a perceptual illusion that challenges these assumptions by demonstrating that healthy (nonamputated) individuals can refer somatic sensations to a discrete volume of empty space and experience having an invisible hand. In 10 behavioral and one fMRI experiment, we characterized the perceptual rules and multisensory brain mechanisms that produced this "invisible hand illusion." Our behavioral results showed that the illusion depends on visuotactile-proprioceptive integration that obeys key spatial and temporal multisensory rules confined to near-personal space. The fMRI results associate the illusion experience with increased activity in regions related to the integration of multisensory body-related signals, most notably the bilateral ventral premotor, intraparietal, and cerebellar cortices. We further showed that a stronger feeling of having an invisible hand is associated with a higher degree of effective connectivity between the intraparietal and ventral premotor cortices. These findings demonstrate that the integration of temporally and spatially congruent multisensory signals in a premotor-intraparietal circuit is sufficient to redefine the spatial boundaries of the bodily self, even when visual information directly contradicts the presence of a physical limb at the location of the perceived illusory hand.

No need for a social cue! A masked magician can also trick the audience in the vanishing ball illusion.

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Thomas, Cyril; Didierjean, André

2016-01-01

In the vanishing ball illusion (VBI), a magician throws a ball up in the air twice, after which he pretends to toss it up again, when in fact it remains secretly concealed in his hand. Observers perceive an imaginary ball disappearing into the air. According to Kuhn and Land (2006), the VBI during the fake throw is mediated by the magician's gaze and/or head direction (also called "social cues") as he looks toward the imaginary ball. The aim of this article is to test an alternative interpretation. According to our hypothesis, the magician's social cues are not essential to the VBI. We compared the numbers of participants experiencing the VBI when the magician's social cues were directed toward the illusory ball and when the magician's social cues were either hidden behind a black mask (Exp. 1) or stationary (Exp. 2). The results showed that the number of observers experiencing the VBI was high (almost two-thirds of the participants), regardless of whether the magician's social cueing was directed toward the illusion, hidden behind a mask, or stationary. In a third experiment (Exp. 3), we replicated Kuhn and Land's initial results and attempted to further explain their "anti-illusion" social-cue effect. This study confirms that social cueing is not required in the VBI: Its presence did not increase the number of participants experiencing the illusion.

White noise speech illusion and psychosis expression : An experimental investigation of psychosis liability

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Pries, Lotta-Katrin; Guloksuz, Sinan; Menne-Lothmann, Claudia; Decoster, Jeroen; van Winkel, Ruud; Collip, Dina; Delespaul, Philippe; De Hert, Marc; Derom, Catherine; Thiery, Evert; Jacobs, Nele; Wichers, Marieke; Simons, Claudia J. P.; Rutten, Bart P. F.; van Os, Jim

2017-01-01

Background: An association between white noise speech illusion and psychotic symptoms has been reported in patients and their relatives. This supports the theory that bottom-up and top-down perceptual processes are involved in the mechanisms underlying perceptual abnormalities. However, findings in

A Virtual Reality Full Body Illusion Improves Body Image Disturbance in Anorexia Nervosa.

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Anouk Keizer

Full Text Available Patients with anorexia nervosa (AN have a persistent distorted experience of the size of their body. Previously we found that the Rubber Hand Illusion improves hand size estimation in this group. Here we investigated whether a Full Body Illusion (FBI affects body size estimation of body parts more emotionally salient than the hand. In the FBI, analogue to the RHI, participants experience ownership over an entire virtual body in VR after synchronous visuo-tactile stimulation of the actual and virtual body.We asked participants to estimate their body size (shoulders, abdomen, hips before the FBI was induced, directly after induction and at ~2 hour 45 minutes follow-up. The results showed that AN patients (N = 30 decrease the overestimation of their shoulders, abdomen and hips directly after the FBI was induced. This effect was strongest for estimates of circumference, and also observed in the asynchronous control condition of the illusion. Moreover, at follow-up, the improvements in body size estimation could still be observed in the AN group. Notably, the HC group (N = 29 also showed changes in body size estimation after the FBI, but the effect showed a different pattern than that of the AN group.The results lead us to conclude that the disturbed experience of body size in AN is flexible and can be changed, even for highly emotional body parts. As such this study offers novel starting points from which new interventions for body image disturbance in AN can be developed.

The elevator illusion results from the combination of body orientation and egocentric perception.

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Paillard, A; Denise, P; Barraud, P-A; Roux, A; Cian, C

2009-10-30

Perception of body orientation and apparent location of objects are altered when humans are using assisted means of locomotion and the resultant of the imposed acceleration and gravity is no longer aligned with the gravitational vertical. As the otolithic system cannot discriminate the acceleration of gravity from sustained inertial accelerations, individuals would perceive the resultant acceleration vector (GiA) as the vertical. However, when subjects are aligned on the GiA, an increase in the magnitude of GiA induced a lowering of the apparent visual horizon (i.e. "elevator illusion"). The main aim of this study was to quantify the contribution of body and egocentric perception in the elevator illusion. While being exposed to 1G and 1.3G and aligned on the GiA acceleration, subjects (N=20) were asked (1) to set a luminous target to the subjective horizon, (2) to set a luminous target on "straight ahead" position (egocentric task) and (3) to rotate a tilting tube to their subjective perception of body orientation. Results showed that increasing GiA lowered horizon and egocentric settings and induces a backward body tilt perception. Moreover, the elevator illusion can be expressed as the additive combination of two processes: one that is dependent on body tilt perception, and the other that is dependent on egocentric perception. Both misperceptions in hypergravity may be considered to be a consequence of excessive shearing of the otolith organs. However large inter-individual differences in body tilt perception were observed. This last result was discussed in terms of the contribution of extravestibular graviceptors.

Bodily illusions disrupt tactile sensations.

Science.gov (United States)

D'Amour, Sarah; Pritchett, Lisa M; Harris, Laurence R

2015-02-01

To accurately interpret tactile information, the brain needs to have an accurate representation of the body to which to refer the sensations. Despite this, body representation has only recently been incorporated into the study of tactile perception. Here, we investigate whether distortions of body representation affect tactile sensations. We perceptually altered the length of the arm and the width of the waist using a tendon vibration illusion and measured spatial acuity and sensitivity. Surprisingly, we found reduction in both tactile acuity and sensitivity thresholds when the arm or waist was perceptually altered, which indicates a general disruption of low-level tactile processing. We postulate that the disruptive changes correspond to the preliminary stage as the body representation starts to change and may give new insights into sensory processing in people with long-term or sudden abnormal body representation such as are found in eating disorders or following amputation.

The changes in perception of visual illusions during long-term isolation

Czech Academy of Sciences Publication Activity Database

Šikl, Radovan; Šimeček, Michal; Lukavský, Jiří

2009-01-01

Roč. 2009, č. 38 (2009), s. 31-32 ISSN 0301-0066. [European Conference on Visual Perception. 24.08.2009-28.08.2009, Regensburg] R&D Projects: GA ČR GA406/09/2003 Institutional research plan: CEZ:AV0Z70250504 Keywords : long-term isolation * geometrical illusions * perspective Subject RIV: AN - Psychology http://www.perceptionweb.com/abstract.cgi?id=v090766

The Illusion of Transparency and Normative Beliefs about Anxiety during Public Speaking

Science.gov (United States)

MacInnis, Cara C.; Mackinnon, Sean P.; MacIntyre, Peter D.

2010-01-01

Public speakers believe their nervousness is more apparent to others than is actually the case, a phenomenon known as the illusion of transparency. Study 1, in which participants delivered a public speech to an audience, provided evidence of this phenomenon. Despite this, a substantial minority of participants (36%) thought that the audience would…

On the susceptibility of adaptive memory to false memory illusions.

Science.gov (United States)

Howe, Mark L; Derbish, Mary H

2010-05-01

Previous research has shown that survival-related processing of word lists enhances retention for that material. However, the claim that survival-related memories are more accurate has only been examined when true recall and recognition of neutral material has been measured. In the current experiments, we examined the adaptive memory superiority effect for different types of processing and material, measuring accuracy more directly by comparing true and false recollection rates. Survival-related information and processing was examined using word lists containing backward associates of neutral, negative, and survival-related critical lures and type of processing (pleasantness, moving, survival) was varied using an incidental memory paradigm. Across four experiments, results showed that survival-related words were more susceptible than negative and neutral words to the false memory illusion and that processing information in terms of its relevance to survival independently increased this susceptibility to the false memory illusion. Overall, although survival-related processing and survival-related information resulted in poorer, not more accurate, memory, such inaccuracies may have adaptive significance. These findings are discussed in the context of false memory research and recent theories concerning the importance of survival processing and the nature of adaptive memory. Copyright 2009 Elsevier B.V. All rights reserved.

Acoustic foundations of the speech-to-song illusion.

Science.gov (United States)

Tierney, Adam; Patel, Aniruddh D; Breen, Mara

2018-06-01

In the "speech-to-song illusion," certain spoken phrases are heard as highly song-like when isolated from context and repeated. This phenomenon occurs to a greater degree for some stimuli than for others, suggesting that particular cues prompt listeners to perceive a spoken phrase as song. Here we investigated the nature of these cues across four experiments. In Experiment 1, participants were asked to rate how song-like spoken phrases were after each of eight repetitions. Initial ratings were correlated with the consistency of an underlying beat and within-syllable pitch slope, while rating change was linked to beat consistency, within-syllable pitch slope, and melodic structure. In Experiment 2, the within-syllable pitch slope of the stimuli was manipulated, and this manipulation changed the extent to which participants heard certain stimuli as more musical than others. In Experiment 3, the extent to which the pitch sequences of a phrase fit a computational model of melodic structure was altered, but this manipulation did not have a significant effect on musicality ratings. In Experiment 4, the consistency of intersyllable timing was manipulated, but this manipulation did not have an effect on the change in perceived musicality after repetition. Our methods provide a new way of studying the causal role of specific acoustic features in the speech-to-song illusion via subtle acoustic manipulations of speech, and show that listeners can rapidly (and implicitly) assess the degree to which nonmusical stimuli contain musical structure. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

An investigation of 3D images of the simultaneous-lightness-contrast illusion using a virtual-reality technique

Directory of Open Access Journals (Sweden)

Menshikova, G.Ya.

2013-09-01

Full Text Available This article investigates the problem of lightness perception. To clarify the role of depth in lightness perception two current models—the albedo hypothesis and the coplanar-ratio hypothesis—are discussed. To compare them the strength of the simultaneous-lightnesscontrast (SLC illusion was investigated as a function of three-dimensional (3D configurations of the test and background squares. In accordance with both hypotheses the changes in the depth arrangements of the test and background squares should result in changes in the illusory effect. However, the reasons for and the directions of these changes should be different. Five different types of 3D configurations were created in which the test squares were tilted at different angles to the background squares. A virtual-reality technique was used to present stereo pairs of different 3D configurations. Thirty-seven observers took part in the experiment. The method of constant stimuli was used to obtain psychometric functions. The displacements of these functions for 3D configurations in comparison with the 2D configuration allowed the estimation of illusion strength. The analysis of individual values of illusion strength revealed two groups of subjects. For the first group (38% of all participants the strength changed insignificantly depending on the 3D configurations. For the second group (62% of all participants significant differences were obtained for those configurations in which the test and background squares were perceived as differently illuminated. The changes in the SLC illusion strength for the second group were consistent with predictions made by the albedo hypothesis. Thus, it seems that the perceived illumination of a surface should be considered the main parameter for lightness estimations in 3D scenes.

Ask a Scientist: What is Color Blindness?

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Full Text Available ... Stuff Cool Eye Tricks Links to More Information Optical Illusions Printables Ask a Scientist Video Series Why can’ ... a scientist? Click to Watch What is an optical illusion? Click to Watch What is color blindness? Click ...

Fiscal Effectiveness and Debt Illusion in a Rational Expectations Model

OpenAIRE

Basil A. DALAMAGAS

1993-01-01

The question of how substitution of debt for taxes affects private sector wealth and consumption has long been an unresolved macroeconomic theory and policy dispute. The present study attempts to address this problem within a modified fiscal-illusion setting, by utilizing an explicit rational expectations optimizing model of consumer behaviour for a sample of six developed countries. The empirical evidence presented is strongly supportive of the assertion that consumers make their consumption...

Seeing the Light: Optics in Nature, Photography, Color, Vision, and Holography

Science.gov (United States)

Falk, David R.; Brill, Dieter R.; Stork, David G.

1985-11-01

The most complete and lucid nonmathematical study of light available. Chapters are self-contained, making the book flexible and easy to read. Coverage includes such non-traditional topics as processes of vision and the eye, atmospherical optical phenomena, color perception and illusions, color in nature and in art, Kirilian photography, and holography. Includes experiments that can be carried out with simple equipment. Chapters contain optional advanced sections, and appendixes review the mathematics for quantitative aspects. Illustrated, including a four-color insert.

Individual Differences in the Rubber Hand Illusion Are Related to Sensory Suggestibility.

Directory of Open Access Journals (Sweden)

Angela Marotta

Full Text Available In the rubber hand illusion (RHI, watching a rubber hand being stroked in synchrony with one's own hidden hand may induce a sense of ownership over the rubber hand. The illusion relies on bottom-up multisensory integration of visual, tactile, and proprioceptive information, and on top-down processes through which the rubber hand is incorporated into pre-existing representations of the body. Although the degree of illusory experience varies largely across individuals, the factors influencing individual differences are unknown. We investigated whether sensory suggestibility might modulate susceptibility to the RHI. Sensory suggestibility is a personality trait related to how individuals react to sensory information. Because of its sensory nature, this trait could be relevant for studies using the RHI paradigm. Seventy healthy volunteers were classified by Sensory Suggestibility Scale (SSS scores as having high or low suggestibility and assigned to either a high- (High-SSS or a low-suggestibility (Low-SSS group. Two components of the RHI were evaluated in synchronous and asynchronous stroking conditions: subjective experience of sense of ownership over the rubber hand via a 9-statement questionnaire, and proprioceptive drift as measured with a ruler. The High-SSS group was generally more susceptible to the subjective component; in the synchronous condition, they rated the statement assessing the sense of ownership higher than the Low-SSS group. The scores for this statement significantly correlated with the total SSS score, indicating that the higher the sensory suggestibility, the stronger the sense of ownership. No effect of sensory suggestibility on proprioceptive drift was observed, suggesting that the effect is specific for the subjective feeling of ownership. This study demonstrates that sensory suggestibility may contribute to participants' experience of the illusion and should be considered when using the RHI paradigm.

Individual Differences in the Rubber Hand Illusion Are Related to Sensory Suggestibility.

Science.gov (United States)

Marotta, Angela; Tinazzi, Michele; Cavedini, Clelia; Zampini, Massimiliano; Fiorio, Mirta

2016-01-01

In the rubber hand illusion (RHI), watching a rubber hand being stroked in synchrony with one's own hidden hand may induce a sense of ownership over the rubber hand. The illusion relies on bottom-up multisensory integration of visual, tactile, and proprioceptive information, and on top-down processes through which the rubber hand is incorporated into pre-existing representations of the body. Although the degree of illusory experience varies largely across individuals, the factors influencing individual differences are unknown. We investigated whether sensory suggestibility might modulate susceptibility to the RHI. Sensory suggestibility is a personality trait related to how individuals react to sensory information. Because of its sensory nature, this trait could be relevant for studies using the RHI paradigm. Seventy healthy volunteers were classified by Sensory Suggestibility Scale (SSS) scores as having high or low suggestibility and assigned to either a high- (High-SSS) or a low-suggestibility (Low-SSS) group. Two components of the RHI were evaluated in synchronous and asynchronous stroking conditions: subjective experience of sense of ownership over the rubber hand via a 9-statement questionnaire, and proprioceptive drift as measured with a ruler. The High-SSS group was generally more susceptible to the subjective component; in the synchronous condition, they rated the statement assessing the sense of ownership higher than the Low-SSS group. The scores for this statement significantly correlated with the total SSS score, indicating that the higher the sensory suggestibility, the stronger the sense of ownership. No effect of sensory suggestibility on proprioceptive drift was observed, suggesting that the effect is specific for the subjective feeling of ownership. This study demonstrates that sensory suggestibility may contribute to participants' experience of the illusion and should be considered when using the RHI paradigm.

Self-face recognition shares brain regions active during proprioceptive illusion in the right inferior fronto-parietal superior longitudinal fasciculus III network.

Science.gov (United States)

Morita, Tomoyo; Saito, Daisuke N; Ban, Midori; Shimada, Koji; Okamoto, Yuko; Kosaka, Hirotaka; Okazawa, Hidehiko; Asada, Minoru; Naito, Eiichi

2017-04-21

Proprioception is somatic sensation that allows us to sense and recognize position, posture, and their changes in our body parts. It pertains directly to oneself and may contribute to bodily awareness. Likewise, one's face is a symbol of oneself, so that visual self-face recognition directly contributes to the awareness of self as distinct from others. Recently, we showed that right-hemispheric dominant activity in the inferior fronto-parietal cortices, which are connected by the inferior branch of the superior longitudinal fasciculus (SLF III), is associated with proprioceptive illusion (awareness), in concert with sensorimotor activity. Herein, we tested the hypothesis that visual self-face recognition shares brain regions active during proprioceptive illusion in the right inferior fronto-parietal SLF III network. We scanned brain activity using functional magnetic resonance imaging while twenty-two right-handed healthy adults performed two tasks. One was a proprioceptive illusion task, where blindfolded participants experienced a proprioceptive illusion of right hand movement. The other was a visual self-face recognition task, where the participants judged whether an observed face was their own. We examined whether the self-face recognition and the proprioceptive illusion commonly activated the inferior fronto-parietal cortices connected by the SLF III in a right-hemispheric dominant manner. Despite the difference in sensory modality and in the body parts involved in the two tasks, both tasks activated the right inferior fronto-parietal cortices, which are likely connected by the SLF III, in a right-side dominant manner. Here we discuss possible roles for right inferior fronto-parietal activity in bodily awareness and self-awareness. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Illusion and reality in the atmospheres of exoplanets

Science.gov (United States)

Deming, L. Drake; Seager, Sara

2017-01-01

The atmospheres of exoplanets reveal all their properties beyond mass, radius, and orbit. Based on bulk densities, we know that exoplanets larger than 1.5 Earth radii must have gaseous envelopes and, hence, atmospheres. We discuss contemporary techniques for characterization of exoplanetary atmospheres. The measurements are difficult, because—even in current favorable cases—the signals can be as small as 0.001% of the host star's flux. Consequently, some early results have been illusory and not confirmed by subsequent investigations. Prominent illusions to date include polarized scattered light, temperature inversions, and the existence of carbon planets. The field moves from the first tentative and often incorrect conclusions, converging to the reality of exoplanetary atmospheres. That reality is revealed using transits for close-in exoplanets and direct imaging for young or massive exoplanets in distant orbits. Several atomic and molecular constituents have now been robustly detected in exoplanets as small as Neptune. In our current observations, the effects of clouds and haze appear ubiquitous. Topics at the current frontier include the measurement of heavy element abundances in giant planets, detection of carbon-based molecules, measurement of atmospheric temperature profiles, definition of heat circulation efficiencies for tidally locked planets, and the push to detect and characterize the atmospheres of super-Earths. Future observatories for this quest include the James Webb Space Telescope and the new generation of extremely large telescopes on the ground. On a more distant horizon, NASA's study concepts for the Habitable Exoplanet Imaging Mission (HabEx) and the Large UV/Optical/Infrared Surveyor (LUVOIR) missions could extend the study of exoplanetary atmospheres to true twins of Earth.

Perceiving Perception

Science.gov (United States)

Vannan, Donald A.

1973-01-01

Suggests an activity designed to stimulate student interest in optical illusions. By preparing posters of a number of optical illusions and mounting them on the classroom wall, many students will be motivated to seek an explanation for these phenomena. (JR)

Visual capture of action, experience of ownership, and the illusion of self-touch: a new rubber hand paradigm.

Science.gov (United States)

Aimola Davies, Anne M; White, Rebekah C; Thew, Graham; Aimola, Natalie M V; Davies, Martin

2010-01-01

A new rubber hand paradigm evokes an illusion with three conceptually distinct components: (i) the participant experiences her/his hidden right hand as administering touch at the location of the examiner's viewed administering hand (visual capture of action); (ii) the participant experiences the examiner's administering hand as being the participant's own hand (experience of ownership); and (iii) the participant experiences her/his two hands as being in contact, as if she/he were touching her/his own hand (illusion of self-touch). The presence of these illusory experiences was confirmed by questionnaire responses and proprioceptive drift data.

The more-or-less morphing face illusion: A case of fixation-dependent modulation

NARCIS (Netherlands)

Lier, R.J. van; Koning, A.R.

2014-01-01

A visual illusion is presented in which the perceived changes in a morphing sequence depend on eye movements. The phenomenon is illustrated using face morphs: when tracking a moving dot superimposed on a face morphing sequence, the changes in the morphing sequence seem rather small, but when the dot

Visual Illusions and the Control of Ball Placement in Goal-Directed Hitting

Science.gov (United States)

Caljouw, Simone R.; Van der Kamp, John; Savelsbergh, Geert J. P.

2010-01-01

When hitting, kicking, or throwing balls at targets, online control in the target area is impossible. We assumed this lack of late corrections in the target area would induce an effect of a single-winged Muller-Lyer illusion on ball placement. After extensive practice in hitting balls to different landing locations, participants (N = 9) had to hit…

Perception-action dissociation generalizes to the size-inertia illusion.

Science.gov (United States)

Platkiewicz, Jonathan; Hayward, Vincent

2014-04-01

Two objects of similar visual aspects and of equal mass, but of different sizes, generally do not elicit the same percept of heaviness in humans. The larger object is consistently felt to be lighter than the smaller, an effect known as the "size-weight illusion." When asked to repeatedly lift the two objects, the grip forces were observed to adapt rapidly to the true object weight while the size-weight illusion persisted, a phenomenon interpreted as a dissociation between perception and action. We investigated whether the same phenomenon can be observed if the mass of an object is available to participants through inertial rather than gravitational cues and if the number and statistics of the stimuli is such that participants cannot remember each individual stimulus. We compared the responses of 10 participants in 2 experimental conditions, where they manipulated 33 objects having uncorrelated masses and sizes, supported by a frictionless, air-bearing slide that could be oriented vertically or horizontally. We also analyzed the participants' anticipatory motor behavior by measuring the grip force before motion onset. We found that the perceptual illusory effect was quantitatively the same in the two conditions and observed that both visual size and haptic mass had a negligible effect on the anticipatory gripping control of the participants in the gravitational and inertial conditions, despite the enormous differences in the mechanics of the two conditions and the large set of uncorrelated stimuli.

Does affective touch influence the virtual reality full body illusion?

OpenAIRE

de Jong, Jutta R; Keizer, Anouk; Engel, Manja M; Dijkerman, H Chris

2017-01-01

The sense of how we experience our physical body as our own represents a fundamental component of human self-awareness. Body ownership can be studied with bodily illusions which are generated by inducing a visuo-tactile conflict where individuals experience illusionary ownership over a fake body or body part, such as a rubber hand. Previous studies showed that different types of touch modulate the strength of experienced ownership over a rubber hand. Specifically, participants experienced mor...

The watercolor illusion and neon color spreading: a unified analysis of new cases and neural mechanisms

Science.gov (United States)

Pinna, Baingio; Grossberg, Stephen

2005-10-01

Coloration and figural properties of neon color spreading and the watercolor illusion are studied using phenomenal and psychophysical observations. Coloration properties of both effects can be reduced to a common limiting condition, a nearby color transition called the two-dot limiting case, which clarifies their perceptual similarities and dissimilarities. The results are explained by the FACADE neural model of biological vision. The model proposes how local properties of color transitions activate spatial competition among nearby perceptual boundaries, with boundaries of lower-contrast edges weakened by competition more than boundaries of higher-contrast edges. This asymmetry induces spreading of more color across these boundaries than conversely. The model also predicts how depth and figure-ground effects are generated in these illusions.

Age is in the Eye of the Beholder: Examining the Cues Employed to Construct the Illusion of Youth in Teen Pornography

OpenAIRE

Peters, Evyn M.; Morrison, Todd G.; McDermott, Daragh T.; Bishop, C. J.; Kiss, Mark

2014-01-01

Past research has identified a subgenre of mainstream pornography that attempts to create the illusion for consumers that sex is occurring between an adult and a minor (i.e., a child or young adolescent under the age of 18). This illusion is established through various textual, verbal, visual, and behavioural cues. Although the construction of adult–minor relationships in pornography has received some scholarly attention, there has been no attempt to investigate this phenomenon within pornogr...

RE-SONANCEI--MaY-19-9-6--------------~------------------------------'5

Indian Academy of Sciences (India)

Page 36: Optical illusions: Oett) Each crosshatched line is a straight line though it appears distorted; (right) a system of concentric circles that appear to be ovals. Page 64: The question on 'Self-Copying Program' in the Think If Over section was posed by 5 K Ghoshal, not V Rajaraman. Page 66: Optical illusion: The optical ...

Deficits in pain perception in borderline personality disorder: results from the thermal grill illusion.

Science.gov (United States)

Bekrater-Bodmann, Robin; Chung, Boo Young; Richter, Ingmarie; Wicking, Manon; Foell, Jens; Mancke, Falk; Schmahl, Christian; Flor, Herta

2015-10-01

It is well documented that borderline personality disorder (BPD) is characterized by reduced pain sensitivity, which might be related to nonsuicidal self-injury and dissociative experiences in patients with BPD. However, it remains an open question whether this insensitivity relies at least partly on altered sensory integration or on an altered evaluation of pain or a combination of both. In this study, we used the thermal grill illusion (TGI), describing a painful sensation induced by the application of alternating cold and warm nonnoxious stimuli, in patients with either current or remitted BPD as well as matched healthy controls. Two additional conditions, applying warm or cold temperatures only, served as control. We further assessed thermal perception, discrimination, and pain thresholds. We found significantly reduced heat and cold pain thresholds for the current BPD group, as well as reduced cold pain thresholds for the remitted BPD group, as compared with the HC group. Current BPD patients perceived a less-intense TGI in terms of induced pain and unpleasantness, while their general ability to perceive this kind of illusion seemed to be unaffected. Thermal grill illusion magnitude was negatively correlated with dissociation and traumatization only in the current BPD patients. These results indicate that higher-order pain perception is altered in current BPD, which seems to normalize after remission. We discuss these findings against the background of neurophysiological evidence for the TGI in general and reduced pain sensitivity in BPD and suggest a relationship to alterations in N-methyl-D-aspartate neurotransmission.

Optical flow optimization using parallel genetic algorithm

Science.gov (United States)

Zavala-Romero, Olmo; Botella, Guillermo; Meyer-Bäse, Anke; Meyer Base, Uwe

2011-06-01

A new approach to optimize the parameters of a gradient-based optical flow model using a parallel genetic algorithm (GA) is proposed. The main characteristics of the optical flow algorithm are its bio-inspiration and robustness against contrast, static patterns and noise, besides working consistently with several optical illusions where other algorithms fail. This model depends on many parameters which conform the number of channels, the orientations required, the length and shape of the kernel functions used in the convolution stage, among many more. The GA is used to find a set of parameters which improve the accuracy of the optical flow on inputs where the ground-truth data is available. This set of parameters helps to understand which of them are better suited for each type of inputs and can be used to estimate the parameters of the optical flow algorithm when used with videos that share similar characteristics. The proposed implementation takes into account the embarrassingly parallel nature of the GA and uses the OpenMP Application Programming Interface (API) to speedup the process of estimating an optimal set of parameters. The information obtained in this work can be used to dynamically reconfigure systems, with potential applications in robotics, medical imaging and tracking.

Body ownership and agency: task-dependent effects of the virtual hand illusion on proprioceptive drift.

Science.gov (United States)

Shibuya, Satoshi; Unenaka, Satoshi; Ohki, Yukari

2017-01-01

Body ownership and agency are fundamental to self-consciousness. These bodily experiences have been intensively investigated using the rubber hand illusion, wherein participants perceive a fake hand as their own. After presentation of the illusion, the position of the participant's hand then shifts toward the location of the fake hand (proprioceptive drift). However, it remains controversial whether proprioceptive drift is able to provide an objective measurement of body ownership, and whether agency also affects drift. Using the virtual hand illusion (VHI), the current study examined the effects of body ownership and agency on proprioceptive drift, with three different visuo-motor tasks. Twenty healthy adults (29.6 ± 9.2 years old) completed VH manipulations using their right hand under a 2 × 2 factorial design (active vs. passive manipulation, and congruent vs. incongruent virtual hand). Prior to and after VH manipulation, three different tasks were performed to assess proprioceptive drift, in which participants were unable to see their real hands. The effects of the VHI on proprioceptive drift were task-dependent. When participants were required to judge the position of their right hand using a ruler, or by reaching toward a visual target, both body ownership and agency modulated proprioceptive drift. Comparatively, when participants aligned both hands, drift was influenced by ownership but not agency. These results suggest that body ownership and agency might differentially modulate various body representations in the brain.

When Does Modality Matter? Perceptual versus Conceptual Fluency-Based Illusions in Recognition Memory

Science.gov (United States)

Miller, Jeremy K.; Lloyd, Marianne E.; Westerman, Deanne L.

2008-01-01

Previous research has shown that illusions of recognition memory based on enhanced perceptual fluency are sensitive to the perceptual match between the study and test phases of an experiment. The results of the current study strengthen that conclusion, as they show that participants will not interpret enhanced perceptual fluency as a sign of…

The predictive power of dividend yields for future inflation: Money illusion or rational causes?

DEFF Research Database (Denmark)

Engsted, Tom; Pedersen, Thomas Quistgaard

slope coefficients that increase numerically with the horizon in regressions of future inflation onto the dividend yield, in accordance with the data. A purely rational version of the model with no money illusion, but with a link from expected inflation to real consumption growth, also generates...

The Role of Head Movements and Signal Spectrum in an Auditory Front/Back Illusion

Directory of Open Access Journals (Sweden)

W Owen Brimijoin

2012-04-01

Full Text Available We used a dynamic auditory spatial illusion to investigate the role of self-motion and acoustics in shaping our spatial percept of the environment. Using motion capture, we smoothly moved a sound source around listeners as a function of their own head movements. A lowpass filtered sound behind a listener that moved in the direction it would have moved if it had been located in the front was perceived as statically located in front. The contrariwise effect occurred if the sound was in front but moved as if it were behind. The illusion was strongest for sounds lowpass filtered at 500 Hz and weakened as a function of increasing lowpass cutoff frequency. The signals with the most high frequency energy were often associated with an unstable location percept that flickered from front to back as self-motion cues and spectral cues for location came into conflict with one another.

A Common Framework for the Analysis of Complex Motion? Standstill and Capture Illusions

Directory of Open Access Journals (Sweden)

Max Reinhard Dürsteler

2014-12-01

Full Text Available A series of illusions was created by presenting stimuli, which consisted of two overlapping surfaces each defined by textures of independent visual features (i.e. modulation of luminance, color, depth, etc.. When presented concurrently with a stationary 2-D luminance texture, observers often fail to perceive the motion of an overlapping stereoscopically defined depth-texture. This illusory motion standstill arises due to a failure to represent two independent surfaces (one for luminance and one for depth textures and motion transparency (the ability to perceive motion of both surfaces simultaneously. Instead the stimulus is represented as a single non-transparent surface taking on the stationary nature of the luminance-defined texture. By contrast, if it is the 2D-luminance defined texture that is in motion, observers often perceive the stationary depth texture as also moving. In this latter case, the failure to represent the motion transparency of the two textures gives rise to illusionary motion capture. Our past work demonstrated that the illusions of motion standstill and motion capture can occur for depth-textures that are rotating, or expanding / contracting, or else spiraling. Here I extend these findings to include stereo-shearing. More importantly, it is the motion (or lack thereof of the luminance texture that determines how the motion of the depth will be perceived. This observation is strongly in favor of a single pathway for complex motion that operates on luminance-defines texture motion signals only. In addition, these complex motion illusions arise with chromatically-defined textures with smooth, transitions between their colors. This suggests that in respect to color motion perception the complex motions’ pathway is only able to accurately process signals from isoluminant colored textures with sharp transitions between colors, and/or moving at high speeds, which is conceivable if it relies on inputs from a hypothetical dual

Success-slope effects on the illusion of control and on remembered success-frequency

Directory of Open Access Journals (Sweden)

Anastasia Ejova

2013-07-01

Full Text Available The illusion of control refers to the inference of action-outcome contingency in situations where outcomes are in fact random. The strength of this illusion has been found to be affected by whether the frequency of successes increases or decreases over repeated trials, in what can be termed a ``success-slope'' effect. Previous studies have generated inconsistent findings regarding the nature of this effect. In this paper we present an experiment (N = 334 that overcomes several methodological limitations within this literature, employing a wider range of dependent measures (measures of two different types of illusory control, primary (by self and secondary (by luck, as well as measures of remembered success-frequency. Results indicate that different dependent measures lead to different effects. On measures of (primary, but not secondary control over the task, scores were highest when the rate of success increased over time. Meanwhile, estimates of success-frequency in the task did not vary across conditions and showed trends consistent with the broader literature on human memory.

ILLUSION, DISILLUSION, AND IRONY IN PSYCHOANALYSIS.

Science.gov (United States)

Steiner, John

2016-04-01

The author draws a parallel between an analyst listening to a patient and a member of an audience watching a play. In both situations, it is important to be able to adopt a dual identity in order to participate in the action through identification and then to withdraw from the identification to adopt the position of an observer. The author discusses two plays, Ibsen's The Wild Duck (1884) and Sophocles's Oedipus the King (5th century BC, a), and concludes that an ironic attitude to these works can help the spectator to adopt these dual identities and to recognize the value of truth, while at the same time appreciating that reality can be harsh and sometimes unbearable. A similar ironic vision in relation to his patients can enable the analyst to retain a respect for truth alongside a sympathetic awareness of the need for illusion. © 2016 The Psychoanalytic Quarterly, Inc.

The magnetic touch illusion: A perceptual correlate of visuo-tactile integration in peripersonal space.

Science.gov (United States)

Guterstam, Arvid; Zeberg, Hugo; Özçiftci, Vedat Menderes; Ehrsson, H Henrik

2016-10-01

To accurately localize our limbs and guide movements toward external objects, the brain must represent the body and its surrounding (peripersonal) visual space. Specific multisensory neurons encode peripersonal space in the monkey brain, and neurobehavioral studies have suggested the existence of a similar representation in humans. However, because peripersonal space lacks a distinct perceptual correlate, its involvement in spatial and bodily perception remains unclear. Here, we show that applying brushstrokes in mid-air at some distance above a rubber hand-without touching it-in synchrony with brushstrokes applied to a participant's hidden real hand results in the illusory sensation of a "magnetic force" between the brush and the rubber hand, which strongly correlates with the perception of the rubber hand as one's own. In eight experiments, we characterized this "magnetic touch illusion" by using quantitative subjective reports, motion tracking, and behavioral data consisting of pointing errors toward the rubber hand in an intermanual pointing task. We found that the illusion depends on visuo-tactile synchrony and exhibits similarities with the visuo-tactile receptive field properties of peripersonal space neurons, featuring a non-linear decay at 40cm that is independent of gaze direction and follows changes in the rubber hand position. Moreover, the "magnetic force" does not penetrate physical barriers, thus further linking this phenomenon to body-specific visuo-tactile integration processes. These findings provide strong support for the notion that multisensory integration within peripersonal space underlies bodily self-attribution. Furthermore, we propose that the magnetic touch illusion constitutes a perceptual correlate of visuo-tactile integration in peripersonal space. Copyright © 2016 The Author(s). Published by Elsevier B.V. All rights reserved.

Agency Enhances Body Ownership Illusion of Being a Virtual Bat

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Andreasen, Anastassia; Nilsson, Niels Chr.; Serafin, Stefania

2018-01-01

This poster describes a within-subject study of agency´s influence on virtual body ownership (VBO) using anatomically similar but morphologically different body of a virtual bat. Paricipants were exposed to flight under four conditions: voluntary movement through virtual environment (VE......) with avatar present, voluntary movement through virtual environment (VE) with avatar absent, voluntary limbs movement without movements through VE, and finally involuntary movement of the avatar through VE. The results suggest that agency enhances VBO illusion the most under participants´ full control during...

Complex cells decrease errors for the Müller-Lyer illusion in a model of the visual ventral stream

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Astrid eZeman

2014-09-01

Full Text Available To improve robustness in object recognition, many artificial visual systems imitate the way in which the human visual cortex encodes object information as a hierarchical set of features. These systems are usually evaluated in terms of their ability to accurately categorize well-defined, unambiguous objects and scenes. In the real world, however, not all objects and scenes are presented clearly, with well-defined labels and interpretations. Visual illusions demonstrate a disparity between perception and objective reality, allowing psychophysicists to methodically manipulate stimuli and study our interpretation of the environment. One prominent effect, the Müller-Lyer illusion, is demonstrated when the perceived length of a line is contracted (or expanded by the addition of arrowheads (or arrow-tails to its ends. HMAX, a benchmark object recognition system, consistently produces a bias when classifying Müller-Lyer images. HMAX is a hierarchical, artificial neural network that imitates the ‘simple’ and ‘complex’ cell layers found in the visual ventral stream. In this study, we perform two experiments to explore the Müller-Lyer illusion in HMAX, asking: 1 How do simple versus complex cell operations within HMAX affect illusory bias and precision? 2 How does varying the position of the figures in the input image affect classification using HMAX? In our first experiment, we assessed classification after traversing each layer of HMAX and found that in general, kernel operations performed by simple cells increase bias and uncertainty while max-pooling operations executed by complex cells decrease bias and uncertainty. In our second experiment, we increased variation in the positions of figures in the input that reduced bias and uncertainty in HMAX. Our findings suggest that the Müller-Lyer illusion is exacerbated by the vulnerability of simple cell operations to positional fluctuations, but ameliorated by the robustness of complex cell

Complex cells decrease errors for the Müller-Lyer illusion in a model of the visual ventral stream.

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Zeman, Astrid; Obst, Oliver; Brooks, Kevin R

2014-01-01

To improve robustness in object recognition, many artificial visual systems imitate the way in which the human visual cortex encodes object information as a hierarchical set of features. These systems are usually evaluated in terms of their ability to accurately categorize well-defined, unambiguous objects and scenes. In the real world, however, not all objects and scenes are presented clearly, with well-defined labels and interpretations. Visual illusions demonstrate a disparity between perception and objective reality, allowing psychophysicists to methodically manipulate stimuli and study our interpretation of the environment. One prominent effect, the Müller-Lyer illusion, is demonstrated when the perceived length of a line is contracted (or expanded) by the addition of arrowheads (or arrow-tails) to its ends. HMAX, a benchmark object recognition system, consistently produces a bias when classifying Müller-Lyer images. HMAX is a hierarchical, artificial neural network that imitates the "simple" and "complex" cell layers found in the visual ventral stream. In this study, we perform two experiments to explore the Müller-Lyer illusion in HMAX, asking: (1) How do simple vs. complex cell operations within HMAX affect illusory bias and precision? (2) How does varying the position of the figures in the input image affect classification using HMAX? In our first experiment, we assessed classification after traversing each layer of HMAX and found that in general, kernel operations performed by simple cells increase bias and uncertainty while max-pooling operations executed by complex cells decrease bias and uncertainty. In our second experiment, we increased variation in the positions of figures in the input images that reduced bias and uncertainty in HMAX. Our findings suggest that the Müller-Lyer illusion is exacerbated by the vulnerability of simple cell operations to positional fluctuations, but ameliorated by the robustness of complex cell responses to such

Evidence for thalamic involvement in the thermal grill illusion: an FMRI study.

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Fredrik Lindstedt

Full Text Available BACKGROUND: Perceptual illusions play an important role in untangling neural mechanisms underlying conscious phenomena. The thermal grill illusion (TGI has been suggested as a promising model for exploring percepts involved in neuropathic pain, such as cold-allodynia (pain arising from contact with innocuous cold. The TGI is an unpleasant/painful sensation from touching juxtapositioned bars of cold and warm innocuous temperatures. AIM: To develop an MRI-compatible TGI-unit and explore the supraspinal correlates of the illusion, using fMRI, in a group of healthy volunteers. METHODS: We constructed a TGI-thermode allowing the rapid presentation of warm(41°C, cold(18°C and interleaved(41°C+18°C = TGI temperatures in an fMRI-environment. Twenty volunteers were tested. The affective-motivational ("unpleasantness" and sensory-disciminatory ("pain-intensity" dimensions of each respective stimulus were rated. Functional images were analyzed at a corrected α-level <0.05. RESULTS: The TGI was rated as significantly more unpleasant and painful than stimulation with each of its constituent temperatures. Also, the TGI was rated as significantly more unpleasant than painful. Thermal stimulation versus neutral baseline revealed bilateral activations of the anterior insulae and fronto-parietal regions. Unlike its constituent temperatures the TGI displayed a strong activation of the right (contralateral thalamus. Exploratory contrasts at a slightly more liberal threshold-level also revealed a TGI-activation of the right mid/anterior insula, correlating with ratings of unpleasantness (rho = 0.31. CONCLUSION/SIGNIFICANCE: To the best of our knowledge, this is the first fMRI-study of the TGI. The activation of the anterior insula is consistent with this region's putative role in processing of homeostatically relevant feeling-states. Our results constitute the first neurophysiologic evidence of thalamic involvement in the TGI. Similar thalamic activity

Alpha motion based on a motion detector, but not on the Müller-Lyer illusion

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Suzuki, Masahiro

2014-07-01

This study examined the mechanism of alpha motion, the apparent motion of the Müller-Lyer figure's shaft that occurs when the arrowheads and arrow tails are alternately presented. The following facts were found: (a) reduced exposure duration decreased the amount of alpha motion, and this phenomenon was not explainable by the amount of the Müller-Lyer illusion; (b) the motion aftereffect occurred after adaptation to alpha motion; (c) occurrence of alpha motion became difficult when the temporal frequency increased, and this characteristic of alpha motion was similar to the characteristic of a motion detector that motion detection became difficult when the temporal frequency increased from the optimal frequency. These findings indicated that alpha motion occurs on the basis of a motion detector but not on the Müller-Lyer illusion, and that the mechanism of alpha motion is the same as that of general motion perception.

Is the Moon Illusion a Celestial Ames Demonstration?

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Brecher, Kenneth

2010-01-01

To most naked eye observers, the Moon appears larger when seen near the horizon than it does when seen near the zenith. This "Moon Illusion” has been reported from as early as the fourth century BC and has been the subject of hundreds of papers and two books. Its explanation does not lie in the realm of physics (atmospheric refraction) or astronomy (eccentric lunar orbit) but, rather, in the realm of visual perception. Theories for the cause of the effect abound but, at present, there is no universally accepted explanation. Because the effect can be easily observed in many locations and during the course of an academic year, the moon illusion can provide a nice astronomical example that involves both direct observations and theoretical analysis. As part of the NSF funded "Project LITE: Light Inquiry Through Experiments", we have been developing inexpensive experiments and demonstrations that can be done at home. One of these is a miniature version of the classic "Ames Room". The life size version was originally developed by Adelbert Ames, Jr. and can be seen in many science museums. Our "digital” Ames Room has been designed to be printed on heavy paper using an inexpensive inkjet printer from a PDF file that is posted on the Project LITE web site http://lite.bu.edu and then cut and folded to make the room. When viewed through one wall using a commonly available door viewer, it dramatically demonstrates how the eye and brain system assesses the relative size of objects by making comparisons with the surrounding environment in which the objects are placed. In this presentation we will discuss some insights that the Ames Room provides that may offer clues to the correct explanation for the Moon Illusion. Project LITE is supported by the NSF through DUE Grant # 0715975.

Individuals Who Believe in the Paranormal Expose Themselves to Biased Information and Develop More Causal Illusions than Nonbelievers in the Laboratory.

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Blanco, Fernando; Barberia, Itxaso; Matute, Helena

2015-01-01

In the reasoning literature, paranormal beliefs have been proposed to be linked to two related phenomena: a biased perception of causality and a biased information-sampling strategy (believers tend to test fewer hypotheses and prefer confirmatory information). In parallel, recent contingency learning studies showed that, when two unrelated events coincide frequently, individuals interpret this ambiguous pattern as evidence of a causal relationship. Moreover, the latter studies indicate that sampling more cause-present cases than cause-absent cases strengthens the illusion. If paranormal believers actually exhibit a biased exposure to the available information, they should also show this bias in the contingency learning task: they would in fact expose themselves to more cause-present cases than cause-absent trials. Thus, by combining the two traditions, we predicted that believers in the paranormal would be more vulnerable to developing causal illusions in the laboratory than nonbelievers because there is a bias in the information they experience. In this study, we found that paranormal beliefs (measured using a questionnaire) correlated with causal illusions (assessed by using contingency judgments). As expected, this correlation was mediated entirely by the believers' tendency to expose themselves to more cause-present cases. The association between paranormal beliefs, biased exposure to information, and causal illusions was only observed for ambiguous materials (i.e., the noncontingent condition). In contrast, the participants' ability to detect causal relationships which did exist (i.e., the contingent condition) was unaffected by their susceptibility to believe in paranormal phenomena.

Individuals Who Believe in the Paranormal Expose Themselves to Biased Information and Develop More Causal Illusions than Nonbelievers in the Laboratory.

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Fernando Blanco

Full Text Available In the reasoning literature, paranormal beliefs have been proposed to be linked to two related phenomena: a biased perception of causality and a biased information-sampling strategy (believers tend to test fewer hypotheses and prefer confirmatory information. In parallel, recent contingency learning studies showed that, when two unrelated events coincide frequently, individuals interpret this ambiguous pattern as evidence of a causal relationship. Moreover, the latter studies indicate that sampling more cause-present cases than cause-absent cases strengthens the illusion. If paranormal believers actually exhibit a biased exposure to the available information, they should also show this bias in the contingency learning task: they would in fact expose themselves to more cause-present cases than cause-absent trials. Thus, by combining the two traditions, we predicted that believers in the paranormal would be more vulnerable to developing causal illusions in the laboratory than nonbelievers because there is a bias in the information they experience. In this study, we found that paranormal beliefs (measured using a questionnaire correlated with causal illusions (assessed by using contingency judgments. As expected, this correlation was mediated entirely by the believers' tendency to expose themselves to more cause-present cases. The association between paranormal beliefs, biased exposure to information, and causal illusions was only observed for ambiguous materials (i.e., the noncontingent condition. In contrast, the participants' ability to detect causal relationships which did exist (i.e., the contingent condition was unaffected by their susceptibility to believe in paranormal phenomena.

A standing posture is associated with increased susceptibility to the sound-induced flash illusion in fall-prone older adults.

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Stapleton, John; Setti, Annalisa; Doheny, Emer P; Kenny, Rose Anne; Newell, Fiona N

2014-02-01

Recent research has provided evidence suggesting a link between inefficient processing of multisensory information and incidence of falling in older adults. Specifically, Setti et al. (Exp Brain Res 209:375-384, 2011) reported that older adults with a history of falling were more susceptible than their healthy, age-matched counterparts to the sound-induced flash illusion. Here, we investigated whether balance control in fall-prone older adults was directly associated with multisensory integration by testing susceptibility to the illusion under two postural conditions: sitting and standing. Whilst standing, fall-prone older adults had a greater body sway than the age-matched healthy older adults and their body sway increased when presented with the audio-visual illusory but not the audio-visual congruent conditions. We also found an increase in susceptibility to the sound-induced flash illusion during standing relative to sitting for fall-prone older adults only. Importantly, no performance differences were found across groups in either the unisensory or non-illusory multisensory conditions across the two postures. These results suggest an important link between multisensory integration and balance control in older adults and have important implications for understanding why some older adults are prone to falling.

Pond of Illusion: Interacting through Mixed Reality

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Nobel-Jørgensen, Morten; Nielsen, Jannik Boll; Larsen, Anders Boesen Lindbo

2013-01-01

Pond of Illusion is a mixed reality installation where a virtual space (the pond) is injected between two real spaces. The users are in either of the real spaces, and they can see each other through windows in the virtual space as illustrated in Figure 1(left). The installation attracts people...... to a large display in either of the real spaces by allowing them to feed virtual fish swimming in the pond. Figure 1(middle) shows how a Microsoft Kinect mounted on top of the display is used for detecting throw motions, which triggers virtual breadcrumbs to be thrown into the pond for feeding the nearby...... fish. Of course, the fish may not be available because they are busy eating what people have thrown into the pond from the other side....

An ordinal model of the McGurk illusion

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Andersen, Tobias

2011-01-01

Audiovisual information is integrated in speech perception. One manifestation of this is the McGurk illusion in which watching the articulating face alters the auditory phonetic percept. Understanding this phenomenon fully requires a computational model with predictive power. Here, we describe...... model it also employed 30 free parameters where the ordinal model needed only 14. Testing the predictive power of the models using a form of cross-validation we found that, although both models performed rather poorly, the ordinal model performed better than the FLMP. Based on these findings we suggest...... that ordinal models generally have greater predictive power because they are constrained by a priori information about the adjacency of phonetic categories....

Proprioceptive body illusions modulate the visual perception of reaching distance.

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Agustin Petroni

Full Text Available The neurobiology of reaching has been extensively studied in human and non-human primates. However, the mechanisms that allow a subject to decide-without engaging in explicit action-whether an object is reachable are not fully understood. Some studies conclude that decisions near the reach limit depend on motor simulations of the reaching movement. Others have shown that the body schema plays a role in explicit and implicit distance estimation, especially after motor practice with a tool. In this study we evaluate the causal role of multisensory body representations in the perception of reachable space. We reasoned that if body schema is used to estimate reach, an illusion of the finger size induced by proprioceptive stimulation should propagate to the perception of reaching distances. To test this hypothesis we induced a proprioceptive illusion of extension or shrinkage of the right index finger while participants judged a series of LEDs as reachable or non-reachable without actual movement. Our results show that reach distance estimation depends on the illusory perceived size of the finger: illusory elongation produced a shift of reaching distance away from the body whereas illusory shrinkage produced the opposite effect. Combining these results with previous findings, we suggest that deciding if a target is reachable requires an integration of body inputs in high order multisensory parietal areas that engage in movement simulations through connections with frontal premotor areas.

Functional Connectivity Analysis of NIRS Data under Rubber Hand Illusion to Find a Biomarker of Sense of Ownership.

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Arizono, Naoki; Ohmura, Yuji; Yano, Shiro; Kondo, Toshiyuki

2016-01-01

The self-identification, which is called sense of ownership, has been researched through methodology of rubber hand illusion (RHI) because of its simple setup. Although studies with neuroimaging technique, such as fMRI, revealed that several brain areas are associated with the sense of ownership, near-infrared spectroscopy (NIRS) has not yet been utilized. Here we introduced an automated setup to induce RHI, measured the brain activity during the RHI with NIRS, and analyzed the functional connectivity so as to understand dynamical brain relationship regarding the sense of ownership. The connectivity was evaluated by multivariate Granger causality. In this experiment, the peaks of oxy-Hb on right frontal and right motor related areas during the illusion were significantly higher compared with those during the nonillusion. Furthermore, by analyzing the NIRS recordings, we found a reliable connectivity from the frontal to the motor related areas during the illusion. This finding suggests that frontal cortex and motor related areas communicate with each other when the sense of ownership is induced. The result suggests that the sense of ownership is related to neural mechanism underlying human motor control, and it would be determining whether motor learning (i.e., neural plasticity) will occur. Thus RHI with the functional connectivity analysis will become an appropriate biomarker for neurorehabilitation.

Neurobiological mechanisms behind the spatiotemporal illusions of awareness that are used for advocating prediction or postdiction

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Talis eBachmann

2013-01-01

Full Text Available The fact that it takes time for the brain to process information from the changing environment underlies many experimental phenomena of awareness of spatiotemporal events, including a number of astonishing illusions. These phenomena have been explained from the predictive and postdictive theoretical perspectives. Here I describe the most extensively studied phenomena in order to see how well the two perspectives can explain them. Next, the neurobiological perceptual retouch mechanism of producing stimulation awareness is characterized and its work in causing the listed illusions is described. A perspective on how brain mechanisms of conscious perception produce the phenomena supportive of the postdictive view is presented in this article. At the same time, some of the phenomena cannot be explained by the traditional postdictive account, but can be interpreted from the perceptual retouch theory perspective.

A method for generating an illusion of backwards time travel using immersive virtual reality - an exploratory study

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Doron eFriedman

2014-09-01

Full Text Available We introduce a new method, based on immersive virtual reality, to give people the illusion of having travelled backwards through time to relive a sequence of events in which they can intervene and change history. The participant had played an important part in events with a tragic outcome - deaths of strangers – by having to choose between saving 5 people or 1. We consider whether the ability to go back through time, and intervene, to possibly avoid all deaths, has an impact on how the participant views such moral dilemmas, and also whether this experience leads to a re-evaluation of past unfortunate events in their own lives. We carried out an exploratory study where in the ‘Time Travel’ condition 16 participants relived these events three times, seeing incarnations of their past selves carrying out the actions that they had previously carried out. In a ‘Repetition’ condition another 16 participants replayed the same situation three times, without any notion of time travel. Our results suggest that those in the Time Travel condition did achieve an illusion of ‘time travel’ provided that they also experienced an illusion of presence in the virtual environment, body ownership and agency over the virtual body that substituted their own. Time travel produced an increase in guilt feelings about the events that had occurred, and an increase in support of utilitarian behavior as the solution to the moral dilemma. Time travel also produced an increase in implicit morality as judged by an implicit association test. The time travel illusion was associated with a reduction of regret associated with bad decisions in their own lives. The results show that when participants have a third action that they can take to solve the moral dilemma (that does not immediately involve choosing between the 1 and the 5 then they tend to take this option, even though it is useless in solving the dilemma, and actually results in the deaths of a greater number.

A method for generating an illusion of backwards time travel using immersive virtual reality—an exploratory study

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Friedman, Doron; Pizarro, Rodrigo; Or-Berkers, Keren; Neyret, Solène; Pan, Xueni; Slater, Mel

2014-01-01

We introduce a new method, based on immersive virtual reality (IVR), to give people the illusion of having traveled backwards through time to relive a sequence of events in which they can intervene and change history. The participant had played an important part in events with a tragic outcome—deaths of strangers—by having to choose between saving 5 people or 1. We consider whether the ability to go back through time, and intervene, to possibly avoid all deaths, has an impact on how the participant views such moral dilemmas, and also whether this experience leads to a re-evaluation of past unfortunate events in their own lives. We carried out an exploratory study where in the “Time Travel” condition 16 participants relived these events three times, seeing incarnations of their past selves carrying out the actions that they had previously carried out. In a “Repetition” condition another 16 participants replayed the same situation three times, without any notion of time travel. Our results suggest that those in the Time Travel condition did achieve an illusion of “time travel” provided that they also experienced an illusion of presence in the virtual environment, body ownership, and agency over the virtual body that substituted their own. Time travel produced an increase in guilt feelings about the events that had occurred, and an increase in support of utilitarian behavior as the solution to the moral dilemma. Time travel also produced an increase in implicit morality as judged by an implicit association test. The time travel illusion was associated with a reduction of regret associated with bad decisions in their own lives. The results show that when participants have a third action that they can take to solve the moral dilemma (that does not immediately involve choosing between the 1 and the 5) then they tend to take this option, even though it is useless in solving the dilemma, and actually results in the deaths of a greater number. PMID:25228889

A method for generating an illusion of backwards time travel using immersive virtual reality-an exploratory study.

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Friedman, Doron; Pizarro, Rodrigo; Or-Berkers, Keren; Neyret, Solène; Pan, Xueni; Slater, Mel

2014-01-01

We introduce a new method, based on immersive virtual reality (IVR), to give people the illusion of having traveled backwards through time to relive a sequence of events in which they can intervene and change history. The participant had played an important part in events with a tragic outcome-deaths of strangers-by having to choose between saving 5 people or 1. We consider whether the ability to go back through time, and intervene, to possibly avoid all deaths, has an impact on how the participant views such moral dilemmas, and also whether this experience leads to a re-evaluation of past unfortunate events in their own lives. We carried out an exploratory study where in the "Time Travel" condition 16 participants relived these events three times, seeing incarnations of their past selves carrying out the actions that they had previously carried out. In a "Repetition" condition another 16 participants replayed the same situation three times, without any notion of time travel. Our results suggest that those in the Time Travel condition did achieve an illusion of "time travel" provided that they also experienced an illusion of presence in the virtual environment, body ownership, and agency over the virtual body that substituted their own. Time travel produced an increase in guilt feelings about the events that had occurred, and an increase in support of utilitarian behavior as the solution to the moral dilemma. Time travel also produced an increase in implicit morality as judged by an implicit association test. The time travel illusion was associated with a reduction of regret associated with bad decisions in their own lives. The results show that when participants have a third action that they can take to solve the moral dilemma (that does not immediately involve choosing between the 1 and the 5) then they tend to take this option, even though it is useless in solving the dilemma, and actually results in the deaths of a greater number.

The accentuation principle of figure-ground segregation and the downbeat illusion.

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Pinna, Baingio; Sirigu, Luca

2016-10-01

Pinna and Sirigu (2011) demonstrated a new principle of grouping, called the accentuation principle, stating that, all else being equal, elements tend to group in the same oriented direction of the discontinuous element placed within a whole set of continuous/homogeneous components. The discontinuous element behaves like an accent, i.e. a visual emphasis within the wholeness of components as shown in the next section. In this work, the accentuation principle has been extended to new visual domains. In particular, it is shown how this principle affects shape perception. Moreover several visual object attributes are also highlighted, among which orientation, spatial position, inner dynamics and apparent motion that determine the so-called organic segmentation and furthermore tend to induce figure-ground segregation. On the basis of the results of experimental phenomenology, the accentuation can be considered as a complex principle ruling grouping, figure-ground segregation, shape and meaning formation. Through a new musical illusion of downbeat, it is also demonstrated that this principle influences perceptual organization not only in space but also in time and, thus, in both visual and musical domains. This illusion can be heard in eight measures of Pagodes, a solo piano music by Claude Debussy (1862-1918), where a strong physical-perceptual discrepancy in terms of upbeats and downbeats inversion is strongly perceived in both staves. Copyright © 2016 Elsevier B.V. All rights reserved.

The Rubber Tail Illusion as Evidence of Body Ownership in Mice.

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Wada, Makoto; Takano, Kouji; Ora, Hiroki; Ide, Masakazu; Kansaku, Kenji

2016-10-26

The ownership of one's body parts represents a fundamental aspect of self-consciousness. Accumulating empirical evidence supports the existence of this concept in humans and nonhuman primates, but it is unclear whether nonprimate mammals experience similar feelings. Therefore, the present study used rubber tails to investigate body ownership in rodents. When the real tails and rubber tails were synchronously stroked, the mice responded as if their own tails were touched when the rubber tails were grasped. In contrast, when the stimuli were delivered asynchronously, there was a significantly lower mean response rate when the rubber tail was grasped. These findings suggest that mice may experience body ownership of their tails, suggestive of the rubber hand illusion in humans. To explore the manner in which the ownership of body parts is experienced, this study specifically used the rubber hand illusion (RHI), in which self-consciousness can be extended out of one's own body. Accumulating empirical evidence supports the existence of this concept in humans and nonhuman primates, but it remains unclear whether nonprimate mammals experience similar feelings. This study demonstrated for the first time that mice may experience body ownership of their tails, which is suggestive of the RHI in humans and provides evidence that may highlight how humans experience the ownership of body parts. Copyright © 2016 the authors 0270-6474/16/3611133-05$15.00/0.

Sensory training with vibration-induced kinesthetic illusions improves proprioceptive integration in patients with Parkinson's disease.

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Ribot-Ciscar, Edith; Aimonetti, Jean-Marc; Azulay, Jean-Philippe

2017-12-15

The present study investigates whether proprioceptive training, based on kinesthetic illusions, can help in re-educating the processing of muscle proprioceptive input, which is impaired in patients with Parkinson's disease (PD). The processing of proprioceptive input before and after training was evaluated by determining the error in the amplitude of voluntary dorsiflexion ankle movement (20°), induced by applying a vibration on the tendon of the gastrocnemius-soleus muscle (a vibration-induced movement error). The training consisted of the subjects focusing their attention upon a series of illusory movements of the ankle. Eleven PD patients and eleven age-matched control subjects were tested. Before training, vibration reduced dorsiflexion amplitude in controls by 4.3° (Pkinesthetic illusions, is a simple means for re-educating the processing of muscle proprioceptive input in PD patients. Such complementary training should be included in rehabilitation programs that presently focus on improving balance and motor performance. Copyright © 2017 Elsevier B.V. All rights reserved.

Easier Seen Than Done: Merely Watching Others Perform Can Foster an Illusion of Skill Acquisition.

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Kardas, Michael; O'Brien, Ed

2018-04-01

Modern technologies such as YouTube afford unprecedented access to the skilled performances of other people. Six experiments ( N = 2,225) reveal that repeatedly watching others can foster an illusion of skill acquisition. The more people merely watch others perform (without actually practicing themselves), the more they nonetheless believe they could perform the skill, too (Experiment 1). However, people's actual abilities-from throwing darts and doing the moonwalk to playing an online game-do not improve after merely watching others, despite predictions to the contrary (Experiments 2-4). What do viewers see that makes them think they are learning? We found that extensive viewing allows people to track what steps to take (Experiment 5) but not how those steps feel when taking them. Accordingly, experiencing a "taste" of performing attenuates the illusion: Watching others juggle but then holding the pins oneself tempers perceived change in one's own ability (Experiment 6). These findings highlight unforeseen problems for self-assessment when watching other people.

Relationship between sensitivity to visuotactile temporal discrepancy and the rubber hand illusion.

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Shimada, Sotaro; Suzuki, Tatsuya; Yoda, Naohiko; Hayashi, Tomoya

2014-08-01

The rubber-hand illusion (RHI) is that the subject feels the visually presented tactile stimulation of an artificial (rubber) hand as their own tactile sensation and is caused by stimulating the rubber and real hands synchronously. Our previous study showed that the RHI was greatly reduced as the visual feedback delay of the tactile stimulation of the hand became longer. In the present study, we investigate the relationship between the attenuation of the RHI and the detection of the delay in two experiments: (1) an RHI experiment and (2) a visuotactile asynchrony detection experiment, in which the subjects underwent tactile stimulation of their hand and judged whether visual feedback was consistent with the touch sensation. In line with our previous study, the RHI was significantly reduced as the delay lengthened. Interestingly, proprioceptive drift declined linearly as the delay increased, while the delay detection rate was better fitted by a non-linear (logistic) function. The illusion score showed the intermittent pattern. We suggest that proprioceptive drift is relevant to the processing of the body schema, whereas the delay detection and the subjective feeling of the RHI are more related to the body image processing. Copyright © 2014 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

Laterality and body ownership: Effect of handedness on experience of the rubber hand illusion.

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Smit, M; Kooistra, D I; van der Ham, I J M; Dijkerman, H C

2017-11-01

Body ownership has mainly been linked to the right hemisphere and larger interhemispheric connectivity has been shown to be associated with greater right hemispheric activation. Mixed-handed participants tend to have more interhemispheric connectivity compared to extreme handed participants. The aim of this study was to examine whether feelings of ownership as assessed with the rubber hand illusion (RHI) are differentiated by handedness and differed between the left and right hand. Sinistrals-, dextrals-, and mixed-handed individuals (n = 63) were subjected to the RHI. Stroking was synchronously and asynchronously performed on both the participant's hand and a rubber hand. Outcome measures were an embodiment questionnaire and proprioceptive drift. In contrast to our hypotheses we show a similar experience of ownership for all groups, which may indicate no hemispheric specialization for the illusion. In addition, plasticity of ownership and body ownership are similar for the left hand and right hand in all participants, which suggests similar representations for both hands in the brain. This might be useful to maintain a coherent sense of the body in space.

Memory-guided saccades show effect of a perceptual illusion whereas visually guided saccades do not.

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Massendari, Delphine; Lisi, Matteo; Collins, Thérèse; Cavanagh, Patrick

2018-01-01

The double-drift stimulus (a drifting Gabor with orthogonal internal motion) generates a large discrepancy between its physical and perceived path. Surprisingly, saccades directed to the double-drift stimulus land along the physical, and not perceived, path (Lisi M, Cavanagh P. Curr Biol 25: 2535-2540, 2015). We asked whether memory-guided saccades exhibited the same dissociation from perception. Participants were asked to keep their gaze centered on a fixation dot while the double-drift stimulus moved back and forth on a linear path in the periphery. The offset of the fixation was the go signal to make a saccade to the target. In the visually guided saccade condition, the Gabor kept moving on its trajectory after the go signal but was removed once the saccade began. In the memory conditions, the Gabor disappeared before or at the same time as the go-signal (0- to 1,000-ms delay) and participants made a saccade to its remembered location. The results showed that visually guided saccades again targeted the physical rather than the perceived location. However, memory saccades, even with 0-ms delay, had landing positions shifted toward the perceived location. Our result shows that memory- and visually guided saccades are based on different spatial information. NEW & NOTEWORTHY We compared the effect of a perceptual illusion on two types of saccades, visually guided vs. memory-guided saccades, and found that whereas visually guided saccades were almost unaffected by the perceptual illusion, memory-guided saccades exhibited a strong effect of the illusion. Our result is the first evidence in the literature to show that visually and memory-guided saccades use different spatial representations.

Obsessive-compulsive Disorder patients have a reduced sense of control on the illusion of control task

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Claire Marie Gillan

2014-03-01

Full Text Available There is disagreement regarding then role of perceived control in obsessive-compulsive disorder (OCD. The present study used a traditional illusion of control paradigm (Alloy & Abramson, 1979 to empirically test control estimation in OCD. Twenty-six OCD patients and 26 matched comparison subjects completed an illusion of control task wherein their goal was to attempt to exert control over a light bulb. The density of reinforcement (high, low and the valence of trials (gain, loss were experimentally manipulated within subjects. Unbeknownst to participants, the illumination of the light bulb was predetermined and irrespective of their behavior. OCD patients exhibited lower estimates of control compared with healthy comparison subjects. There were no interactions between group and outcome density or group and valence. We found that OCD patients endorse lower estimates of control than comparison subjects. This finding highlights a potential role for contingency learning in the disorder.

DEMAND ILLUSION AS A WAY TO REDUCE COSTS

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Kirill N. Sosnovskij

2014-01-01

Full Text Available Article devoted to a technique that reduces costs to retailers, as well as increase the speed of discounted products. This article deals with the laws of visual merchandising that have a significant impact on the implementation of the company’s products. The analysis of the first law, with the subsequent introduction into it of a new additional method. Consider the effect of «Illusion of deficit» arising from the application of the proposed method. The article also defines the basic hypothesis of the existence of methods and effect, and the conditions for their effective implementation. To confirm the effectiveness of the developed method, quantitative surveys are conducted for different age groups creating situational model, which allows respondents to feel as a consumer.

Functional Connectivity Analysis of NIRS Data under Rubber Hand Illusion to Find a Biomarker of Sense of Ownership

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Naoki Arizono

2016-01-01

Full Text Available The self-identification, which is called sense of ownership, has been researched through methodology of rubber hand illusion (RHI because of its simple setup. Although studies with neuroimaging technique, such as fMRI, revealed that several brain areas are associated with the sense of ownership, near-infrared spectroscopy (NIRS has not yet been utilized. Here we introduced an automated setup to induce RHI, measured the brain activity during the RHI with NIRS, and analyzed the functional connectivity so as to understand dynamical brain relationship regarding the sense of ownership. The connectivity was evaluated by multivariate Granger causality. In this experiment, the peaks of oxy-Hb on right frontal and right motor related areas during the illusion were significantly higher compared with those during the nonillusion. Furthermore, by analyzing the NIRS recordings, we found a reliable connectivity from the frontal to the motor related areas during the illusion. This finding suggests that frontal cortex and motor related areas communicate with each other when the sense of ownership is induced. The result suggests that the sense of ownership is related to neural mechanism underlying human motor control, and it would be determining whether motor learning (i.e., neural plasticity will occur. Thus RHI with the functional connectivity analysis will become an appropriate biomarker for neurorehabilitation.

Self-Face Recognition Begins to Share Active Region in Right Inferior Parietal Lobule with Proprioceptive Illusion During Adolescence.

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Morita, Tomoyo; Saito, Daisuke N; Ban, Midori; Shimada, Koji; Okamoto, Yuko; Kosaka, Hirotaka; Okazawa, Hidehiko; Asada, Minoru; Naito, Eiichi

2018-04-01

We recently reported that right-side dominance of the inferior parietal lobule (IPL) in self-body recognition (proprioceptive illusion) task emerges during adolescence in typical human development. Here, we extend this finding by demonstrating that functional lateralization to the right IPL also develops during adolescence in another self-body (specifically a self-face) recognition task. We collected functional magnetic resonance imaging (fMRI) data from 60 right-handed healthy children (8-11 years), adolescents (12-15 years), and adults (18-23 years; 20 per group) while they judged whether a presented face was their own (Self) or that of somebody else (Other). We also analyzed fMRI data collected while they performed proprioceptive illusion task. All participants performed self-face recognition with high accuracy. Among brain regions where self-face-related activity (Self vs. Other) developed, only right IPL activity developed predominantly for self-face processing, with no substantial involvement in other-face processing. Adult-like right-dominant use of IPL emerged during adolescence, but was not yet present in childhood. Adult-like common activation between the tasks also emerged during adolescence. Adolescents showing stronger right-lateralized IPL activity during illusion also showed this during self-face recognition. Our results suggest the importance of the right IPL in neuronal processing of information associated with one's own body in typically developing humans.

The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can "see the magic" as well.

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Fuss, Theodora; Bleckmann, Horst; Schluessel, Vera

2014-01-01

Bamboo sharks (Chiloscyllium griseum) were tested for their ability to perceive subjective and illusionary contours as well as line length illusions. Individuals were first trained to differentiate between squares, triangles, and rhomboids in a series of two alternative forced-choice experiments. Transfer tests then elucidated whether Kanizsa squares and triangles, grating gaps and phase shifted abutting gratings were also perceived and distinguished. The visual systems of most vertebrates and even invertebrates perceive illusionary contours despite the absence of physical luminance, color or textural differences. Sharks are no exception to the rule; all tasks were successfully mastered within 3-24 training sessions, with sharks discriminating between various sets of Kanizsa figures and alternative stimuli, as well as between subjective contours in >75% of all tests. However, in contrast to Kanizsa figures and subjective contours, sharks were not deceived by Müller-Lyer (ML) illusions. Here, two center lines of equal length are comparatively set between two arrowheads or -tails, in which case the line featuring the two arrow tails appears to be longer to most humans, primates and birds. In preparation for this experiment, lines of varying length, and lines of unequal length randomly featuring either two arrowheads or -tails on their ends, were presented first. Both sets of lines were successfully distinguished by most sharks. However, during presentation of the ML illusions sharks failed to succeed and succumbed either to side preferences or chose according to chance.

Incorporating Animation Concepts and Principles in STEM Education

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Harrison, Henry L., III; Hummell, Laura J.

2010-01-01

Animation is the rapid display of a sequence of static images that creates the illusion of movement. This optical illusion is often called perception of motion, persistence of vision, illusion of motion, or short-range apparent motion. The phenomenon occurs when the eye is exposed to rapidly changing still images, with each image being changed…

Chaos in balance: non-linear measures of postural control predict individual variations in visual illusions of motion.

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Deborah Apthorp

Full Text Available Visually-induced illusions of self-motion (vection can be compelling for some people, but they are subject to large individual variations in strength. Do these variations depend, at least in part, on the extent to which people rely on vision to maintain their postural stability? We investigated by comparing physical posture measures to subjective vection ratings. Using a Bertec balance plate in a brightly-lit room, we measured 13 participants' excursions of the centre of foot pressure (CoP over a 60-second period with eyes open and with eyes closed during quiet stance. Subsequently, we collected vection strength ratings for large optic flow displays while seated, using both verbal ratings and online throttle measures. We also collected measures of postural sway (changes in anterior-posterior CoP in response to the same visual motion stimuli while standing on the plate. The magnitude of standing sway in response to expanding optic flow (in comparison to blank fixation periods was predictive of both verbal and throttle measures for seated vection. In addition, the ratio between eyes-open and eyes-closed CoP excursions during quiet stance (using the area of postural sway significantly predicted seated vection for both measures. Interestingly, these relationships were weaker for contracting optic flow displays, though these produced both stronger vection and more sway. Next we used a non-linear analysis (recurrence quantification analysis, RQA of the fluctuations in anterior-posterior position during quiet stance (both with eyes closed and eyes open; this was a much stronger predictor of seated vection for both expanding and contracting stimuli. Given the complex multisensory integration involved in postural control, our study adds to the growing evidence that non-linear measures drawn from complexity theory may provide a more informative measure of postural sway than the conventional linear measures.

To be or not to be: the self as illusion.

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Tippett, Krista; Metzinger, Thomas; Thompson, Evan; van Lommel, Pim

2011-10-01

Moderated by Krista Tippett, creator and host of America Public Media's On Being, philosophers Thomas Metzinger (University of Mainz, Germany) and Evan Thompson (University of Toronto) join cardiologist and expert on near-death experiences Pim van Lommel (Hospital Rijnstate, the Netherlands) to examine recent developments in neuroscience and philosophy that shed light on whether our conscious experience of a unified self is reality or illusion. The following is an edited transcript of the discussion that occurred December 7, 2010, 6:00-7:30 PM, at the New York Academy of Sciences in New York City. © 2011 New York Academy of Sciences.

Are You Suggesting That's My Hand? The Relation Between Hypnotic Suggestibility and the Rubber Hand Illusion.

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Walsh, E; Guilmette, D N; Longo, M R; Moore, J W; Oakley, D A; Halligan, P W; Mehta, M A; Deeley, Q

2015-01-01

Hypnotic suggestibility (HS) is the ability to respond automatically to suggestions and to experience alterations in perception and behavior. Hypnotically suggestible participants are also better able to focus and sustain their attention on an experimental stimulus. The present study explores the relation between HS and susceptibility to the rubber hand illusion (RHI). Based on previous research with visual illusions, it was predicted that higher HS would lead to a stronger RHI. Two behavioral output measures of the RHI, an implicit (proprioceptive drift) and an explicit (RHI questionnaire) measure, were correlated against HS scores. Hypnotic suggestibility correlated positively with the implicit RHI measure contributing to 30% of the variation. However, there was no relation between HS and the explicit RHI questionnaire measure, or with compliance control items. High hypnotic suggestibility may facilitate, via attentional mechanisms, the multisensory integration of visuoproprioceptive inputs that leads to greater perceptual mislocalization of a participant's hand. These results may provide insight into the multisensory brain mechanisms involved in our sense of embodiment.

The more-or-less morphing face illusion: a case of fixation-dependent modulation.

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Van Lier, Rob; Koning, Arno

2014-01-01

A visual illusion is presented in which the perceived changes in a morphing sequence depend on eye movements. The phenomenon is illustrated using face morphs: when tracking a moving dot superimposed on a face morphing sequence, the changes in the morphing sequence seem rather small, but when the dot stops moving, the perceived extent of morphing suddenly becomes much larger. We explore this phenomenon further and discuss the observed effects.

Three-dimensional illusion thermal device for location camouflage.

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Wang, Jing; Bi, Yanqiang; Hou, Quanwen

2017-08-08

Thermal metamaterials, proposed in recent years, provide a new method to manipulate the energy flux in heat transfer, and result in many novel thermal devices. In this paper, an illusion thermal device for location camouflage in 3-dimensional heat conduction regime is proposed based on the transformation thermodynamics. The heat source covered by the device produces a fake signal outside the device, which makes the source look like appearing at another position away from its real position. The parameters required by the device are deduced and the method is validated by simulations. The possible scheme to obtain the thermal conductivities required in the device by composing natural materials is supplied, and the influence of some problems in practical fabrication process of the device on the effect of the camouflage is also discussed.

Dynamic causal modeling of touch-evoked potentials in the rubber hand illusion.

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Zeller, Daniel; Friston, Karl J; Classen, Joseph

2016-09-01

The neural substrate of bodily ownership can be disclosed by the rubber hand illusion (RHI); namely, the illusory self-attribution of an artificial hand that is induced by synchronous tactile stimulation of the subject's hand that is hidden from view. Previous studies have pointed to the premotor cortex (PMC) as a pivotal area in such illusions. To investigate the effective connectivity between - and within - sensory and premotor areas involved in bodily perceptions, we used dynamic causal modeling of touch-evoked responses in 13 healthy subjects. Each subject's right hand was stroked while viewing their own hand ("REAL"), or an artificial hand presented in an anatomically plausible ("CONGRUENT") or implausible ("INCONGRUENT") position. Bayesian model comparison revealed strong evidence for a differential involvement of the PMC in the generation of touch-evoked responses under the three conditions, confirming a crucial role of PMC in bodily self-attribution. In brief, the extrinsic (forward) connection from left occipital cortex to left PMC was stronger for CONGRUENT and INCONGRUENT as compared to REAL, reflecting the augmentation of bottom-up visual input when multisensory integration is challenged. Crucially, intrinsic connectivity in the primary somatosensory cortex (S1) was attenuated in the CONGRUENT condition, during the illusory percept. These findings support predictive coding models of the functional architecture of multisensory integration (and attenuation) in bodily perceptual experience. Copyright © 2016 Elsevier Inc. All rights reserved.

Development of Right-hemispheric Dominance of Inferior Parietal Lobule in Proprioceptive Illusion Task

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Naito, Eiichi; Morita, Tomoyo; Saito, Daisuke N; Ban, Midori; Shimada, Koji; Okamoto, Yuko; Kosaka, Hirotaka; Okazawa, Hidehiko; Asada, Minoru

2017-01-01

Abstract Functional lateralization can be an indicator of brain maturation. We have consistently shown that, in the adult brain, proprioceptive processing of muscle spindle afferents generating illusory movement of the right hand activates inferior frontoparietal cortical regions in a right-side dominant manner in addition to the cerebrocerebellar motor network. Here we provide novel evidence regarding the development of the right-dominant use of the inferior frontoparietal cortical regions in humans using this task. We studied brain activity using functional magnetic resonance imaging while 60 right-handed blindfolded healthy children (8–11 years), adolescents (12–15 years), and young adults (18–23 years) (20 per group) experienced the illusion. Adult-like right-dominant use of the inferior parietal lobule (IPL) was observed in adolescents, while children used the IPL bilaterally. In contrast, adult-like lateralized cerebrocerebellar motor activation patterns were already observable in children. The right-side dominance progresses during adolescence along with the suppression of the left-sided IPL activity that emerges during childhood. Therefore, the neuronal processing implemented in the adult's right IPL during the proprioceptive illusion task is likely mediated bilaterally during childhood, and then becomes right-lateralized during adolescence at a substantially later time than the lateralized use of the cerebrocerebellar motor system for kinesthetic processing. PMID:28968653

Motivation with Depth.

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DiSpezio, Michael A.

2000-01-01

Presents an illusional arena by offering experience in optical illusions in which students must apply critical analysis to their innate information gathering systems. Introduces different types of depth illusions for students to experience. (ASK)

Kandó-Melocco, Ferenc. 2015. An Anti-Nazi at Hitler's Table: Political Memoirs of a Hungarian Nobleman Who Dared to Oppose Both Hitler and the Communists. (trans. and ed. Esther Kando Odescalchi. North Charleston, SC: CreateSpace. 162 pp., Illus.; Odescalchi, Esther Kando. 2016. My Escape: Memoirs of a Hungarian Teenage Freedom Fighter. North Charleston, SC: CreateSpace. Illus. 148 pp.

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Ruth G. Biro

2017-09-01

Full Text Available Kandó-Melocco, Ferenc. 2015. An Anti-Nazi at Hitler's Table: Political Memoirs of a Hungarian Nobleman Who Dared to Oppose Both Hitler and the Communists. (trans. and ed. Esther Kando Odescalchi. North Charleston, SC: CreateSpace. 162 pp., Illus.; Odescalchi, Esther Kando. 2016. My Escape: Memoirs of a Hungarian Teenage Freedom Fighter. North Charleston, SC: CreateSpace. Illus. 148 pp.

The brain creates illusions not just for us: sharks (Chiloscyllium griseum can ‘see the magic’ as well.

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Theodora eFuss

2014-03-01

Full Text Available Bamboo sharks (Chiloscyllium griseum were tested for their ability to perceive subjective and illusionary contours as well as line length illusions. Individuals were first trained to differentiate between squares, triangles and rhomboids in a series of two alternative forced-choice experiments. Transfer tests then elucidated whether Kanizsa squares and triangles, grating gaps and phase shifted abutting gratings were also perceived and distinguished. The visual systems of most vertebrates and even invertebrates perceive illusionary contours despite the absence of physical luminance, colour or textural differences. Sharks are no exception to the rule; all tasks were successfully mastered within 3 to 24 training sessions, with sharks discriminating between various sets of Kanizsa figures and alternative stimuli, as well as between subjective contours in >75% of all tests. However, in contrast to Kanizsa figures and subjective contours, sharks were not deceived by Müller-Lyer (ML illusions. Here, two centre lines of equal length are comparatively set between two arrowheads or –tails, in which case the line featuring the two arrow tails appears to be longer to most humans, primates and birds. In preparation for this experiment, lines of varying length, and lines of unequal length randomly featuring either two arrowheads or -tails on their ends, were presented first. Both sets of lines were successfully distinguished by most sharks. However, during presentation of the ML illusions sharks failed to succeed and succumbed either to side preferences or chose according to chance.

The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can “see the magic” as well

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Fuss, Theodora; Bleckmann, Horst; Schluessel, Vera

2014-01-01

Bamboo sharks (Chiloscyllium griseum) were tested for their ability to perceive subjective and illusionary contours as well as line length illusions. Individuals were first trained to differentiate between squares, triangles, and rhomboids in a series of two alternative forced-choice experiments. Transfer tests then elucidated whether Kanizsa squares and triangles, grating gaps and phase shifted abutting gratings were also perceived and distinguished. The visual systems of most vertebrates and even invertebrates perceive illusionary contours despite the absence of physical luminance, color or textural differences. Sharks are no exception to the rule; all tasks were successfully mastered within 3–24 training sessions, with sharks discriminating between various sets of Kanizsa figures and alternative stimuli, as well as between subjective contours in >75% of all tests. However, in contrast to Kanizsa figures and subjective contours, sharks were not deceived by Müller-Lyer (ML) illusions. Here, two center lines of equal length are comparatively set between two arrowheads or –tails, in which case the line featuring the two arrow tails appears to be longer to most humans, primates and birds. In preparation for this experiment, lines of varying length, and lines of unequal length randomly featuring either two arrowheads or -tails on their ends, were presented first. Both sets of lines were successfully distinguished by most sharks. However, during presentation of the ML illusions sharks failed to succeed and succumbed either to side preferences or chose according to chance. PMID:24688458

Using visuo-kinetic virtual reality to induce illusory spinal movement: the MoOVi Illusion.

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Harvie, Daniel S; Smith, Ross T; Hunter, Estin V; Davis, Miles G; Sterling, Michele; Moseley, G Lorimer

2017-01-01

Illusions that alter perception of the body provide novel opportunities to target brain-based contributions to problems such as persistent pain. One example of this, mirror therapy, uses vision to augment perceived movement of a painful limb to treat pain. Since mirrors can't be used to induce augmented neck or other spinal movement, we aimed to test whether such an illusion could be achieved using virtual reality, in advance of testing its potential therapeutic benefit. We hypothesised that perceived head rotation would depend on visually suggested movement. In a within-subjects repeated measures experiment, 24 healthy volunteers performed neck movements to 50 o of rotation, while a virtual reality system delivered corresponding visual feedback that was offset by a factor of 50%-200%-the Motor Offset Visual Illusion (MoOVi)-thus simulating more or less movement than that actually occurring. At 50 o of real-world head rotation, participants pointed in the direction that they perceived they were facing. The discrepancy between actual and perceived direction was measured and compared between conditions. The impact of including multisensory (auditory and visual) feedback, the presence of a virtual body reference, and the use of 360 o immersive virtual reality with and without three-dimensional properties, was also investigated. Perception of head movement was dependent on visual-kinaesthetic feedback ( p  = 0.001, partial eta squared = 0.17). That is, altered visual feedback caused a kinaesthetic drift in the direction of the visually suggested movement. The magnitude of the drift was not moderated by secondary variables such as the addition of illusory auditory feedback, the presence of a virtual body reference, or three-dimensionality of the scene. Virtual reality can be used to augment perceived movement and body position, such that one can perform a small movement, yet perceive a large one. The MoOVi technique tested here has clear potential for assessment and

Using visuo-kinetic virtual reality to induce illusory spinal movement: the MoOVi Illusion

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Daniel S. Harvie

2017-02-01

Full Text Available Background Illusions that alter perception of the body provide novel opportunities to target brain-based contributions to problems such as persistent pain. One example of this, mirror therapy, uses vision to augment perceived movement of a painful limb to treat pain. Since mirrors can’t be used to induce augmented neck or other spinal movement, we aimed to test whether such an illusion could be achieved using virtual reality, in advance of testing its potential therapeutic benefit. We hypothesised that perceived head rotation would depend on visually suggested movement. Method In a within-subjects repeated measures experiment, 24 healthy volunteers performed neck movements to 50o of rotation, while a virtual reality system delivered corresponding visual feedback that was offset by a factor of 50%–200%—the Motor Offset Visual Illusion (MoOVi—thus simulating more or less movement than that actually occurring. At 50o of real-world head rotation, participants pointed in the direction that they perceived they were facing. The discrepancy between actual and perceived direction was measured and compared between conditions. The impact of including multisensory (auditory and visual feedback, the presence of a virtual body reference, and the use of 360o immersive virtual reality with and without three-dimensional properties, was also investigated. Results Perception of head movement was dependent on visual-kinaesthetic feedback (p = 0.001, partial eta squared = 0.17. That is, altered visual feedback caused a kinaesthetic drift in the direction of the visually suggested movement. The magnitude of the drift was not moderated by secondary variables such as the addition of illusory auditory feedback, the presence of a virtual body reference, or three-dimensionality of the scene. Discussion Virtual reality can be used to augment perceived movement and body position, such that one can perform a small movement, yet perceive a large one. The Mo

Source Illusion Devices for Flexural Lamb Waves Using Elastic Metasurfaces.

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Liu, Yongquan; Liang, Zixian; Liu, Fu; Diba, Owen; Lamb, Alistair; Li, Jensen

2017-07-21

Inspired by recent demonstrations of metasurfaces in achieving reduced versions of electromagnetic cloaks, we propose and experimentally demonstrate source illusion devices to manipulate flexural waves using metasurfaces. The approach is particularly useful for elastic waves due to the lack of form invariance in usual transformation methods. We demonstrate compact and simple-to-implement metasurfaces for shifting, transforming, and splitting a point source. The effects are measured to be broadband and robust against a change of source positions, with agreement from numerical simulations and the Huygens-Fresnel theory. The proposed method is potentially useful for applications such as nondestructive testing, high-resolution ultrasonography, and advanced signal modulation.

Visual illusions and ethnocentrism: exemplars for teaching cross-cultural concepts.

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Keith, Kenneth D

2012-05-01

This article discusses the origins of cross-cultural interest in two concepts fundamental to psychology students' views of the world: simple visual illusions and ethnocentrism. Although students encounter these ideas in introductory psychology, textbooks rarely describe the nature or origin of cross-cultural knowledge about them. The article presents a brief account of the history of these concepts and relates them to contemporary notions of psychology and culture. Using visual perception and ethnocentrism as examples, the article suggests the importance of teaching that different people see the world in different ways and the role of that lesson in a future demanding increased cross-cultural understanding.

People Interview: The science behind the 'magic'

Science.gov (United States)

2010-01-01

INTERVIEW The science behind the 'magic' Grand Illusions is a website dedicated to science-based phenomena, fun and games, and optical illusions. David Smith speaks to two of its key members—Hendrik Ball and Tim Rowett.

The second me: Seeing the real body during humanoid robot embodiment produces an illusion of bi-location.

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Aymerich-Franch, Laura; Petit, Damien; Ganesh, Gowrishankar; Kheddar, Abderrahmane

2016-11-01

Whole-body embodiment studies have shown that synchronized multi-sensory cues can trick a healthy human mind to perceive self-location outside the bodily borders, producing an illusion that resembles an out-of-body experience (OBE). But can a healthy mind also perceive the sense of self in more than one body at the same time? To answer this question, we created a novel artificial reduplication of one's body using a humanoid robot embodiment system. We first enabled individuals to embody the humanoid robot by providing them with audio-visual feedback and control of the robot head movements and walk, and then explored the self-location and self-identification perceived by them when they observed themselves through the embodied robot. Our results reveal that, when individuals are exposed to the humanoid body reduplication, they experience an illusion that strongly resembles heautoscopy, suggesting that a healthy human mind is able to bi-locate in two different bodies simultaneously. Copyright © 2016 Elsevier Inc. All rights reserved.

The person in the mirror: using the enfacement illusion to investigate the experiential structure of self-identification.

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Tajadura-Jiménez, Ana; Longo, Matthew R; Coleman, Rosie; Tsakiris, Manos

2012-12-01

How do we acquire a mental representation of our own face? Recently, synchronous, but not asynchronous, interpersonal multisensory stimulation (IMS) between one's own and another person's face has been used to evoke changes in self-identification (enfacement illusion). We investigated the conscious experience of these changes with principal component analyses (PCA) that revealed that while the conscious experience during synchronous IMS focused on resemblance and similarity with the other's face, during asynchronous IMS it focused on multisensory stimulation. Analyses of the identified common factor structure revealed significant quantitative differences between synchronous and asynchronous IMS on self-identification and perceived similarity with the other's face. Experiment 2 revealed that participants with lower interoceptive sensitivity experienced stronger enfacement illusion. Overall, self-identification and body-ownership rely on similar basic mechanisms of multisensory integration, but the effects of multisensory input on their experience are qualitatively different, possibly underlying the face's unique role as a marker of selfhood. Copyright © 2012 Elsevier Inc. All rights reserved.

Visual illusion of tool use recalibrates tactile perception

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Miller, Luke E.; Longo, Matthew R.; Saygin, Ayse P.

2018-01-01

Brief use of a tool recalibrates multisensory representations of the user’s body, a phenomenon called tool embodiment. Despite two decades of research, little is known about its boundary conditions. It has been widely argued that embodiment requires active tool use, suggesting a critical role for somatosensory and motor feedback. The present study used a visual illusion to cast doubt on this view. We used a mirror-based setup to induce a visual experience of tool use with an arm that was in fact stationary. Following illusory tool use, tactile perception was recalibrated on this stationary arm, and with equal magnitude as physical use. Recalibration was not found following illusory passive tool holding, and could not be accounted for by sensory conflict or general interhemispheric plasticity. These results suggest visual tool-use signals play a critical role in driving tool embodiment. PMID:28196765

San Lorenzo and the Poggendorff Illusion in Ravenna

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Olga Daneyko

2011-06-01

Full Text Available In the Mausoleum of Galla Placidia (Ravenna, Italy, the San Lorenzo lunette shows two peculiar visual effects: a transparency effect of gold seen through gold and perceptual collinearity between two parts of a cross which are physically misaligned. Both effects are found within the area of the halo surrounding the saint's head. In this work we addressed the problem posed by the physical misalignment of the cross. Our hypothesis is that the physical misalignment went unnoticed throughout history because the artist produced a perceptual alignment to correct for the Poggendorff illusion. Hence, we asked observers to align two ends of a cross in a reproduction showing the silhouette of San Lorenzo's torso holding the cross. Results support our hypothesis: both direction and magnitude of adjustments comply with the alignment in the original mosaic.

The Pareidolia Test: A Simple Neuropsychological Test Measuring Visual Hallucination-Like Illusions.

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Mamiya, Yasuyuki; Nishio, Yoshiyuki; Watanabe, Hiroyuki; Yokoi, Kayoko; Uchiyama, Makoto; Baba, Toru; Iizuka, Osamu; Kanno, Shigenori; Kamimura, Naoto; Kazui, Hiroaki; Hashimoto, Mamoru; Ikeda, Manabu; Takeshita, Chieko; Shimomura, Tatsuo; Mori, Etsuro

2016-01-01

Visual hallucinations are a core clinical feature of dementia with Lewy bodies (DLB), and this symptom is important in the differential diagnosis and prediction of treatment response. The pareidolia test is a tool that evokes visual hallucination-like illusions, and these illusions may be a surrogate marker of visual hallucinations in DLB. We created a simplified version of the pareidolia test and examined its validity and reliability to establish the clinical utility of this test. The pareidolia test was administered to 52 patients with DLB, 52 patients with Alzheimer's disease (AD) and 20 healthy controls (HCs). We assessed the test-retest/inter-rater reliability using the intra-class correlation coefficient (ICC) and the concurrent validity using the Neuropsychiatric Inventory (NPI) hallucinations score as a reference. A receiver operating characteristic (ROC) analysis was used to evaluate the sensitivity and specificity of the pareidolia test to differentiate DLB from AD and HCs. The pareidolia test required approximately 15 minutes to administer, exhibited good test-retest/inter-rater reliability (ICC of 0.82), and moderately correlated with the NPI hallucinations score (rs = 0.42). Using an optimal cut-off score set according to the ROC analysis, and the pareidolia test differentiated DLB from AD with a sensitivity of 81% and a specificity of 92%. Our study suggests that the simplified version of the pareidolia test is a valid and reliable surrogate marker of visual hallucinations in DLB.

The Pareidolia Test: A Simple Neuropsychological Test Measuring Visual Hallucination-Like Illusions.

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Yasuyuki Mamiya

Full Text Available Visual hallucinations are a core clinical feature of dementia with Lewy bodies (DLB, and this symptom is important in the differential diagnosis and prediction of treatment response. The pareidolia test is a tool that evokes visual hallucination-like illusions, and these illusions may be a surrogate marker of visual hallucinations in DLB. We created a simplified version of the pareidolia test and examined its validity and reliability to establish the clinical utility of this test.The pareidolia test was administered to 52 patients with DLB, 52 patients with Alzheimer's disease (AD and 20 healthy controls (HCs. We assessed the test-retest/inter-rater reliability using the intra-class correlation coefficient (ICC and the concurrent validity using the Neuropsychiatric Inventory (NPI hallucinations score as a reference. A receiver operating characteristic (ROC analysis was used to evaluate the sensitivity and specificity of the pareidolia test to differentiate DLB from AD and HCs.The pareidolia test required approximately 15 minutes to administer, exhibited good test-retest/inter-rater reliability (ICC of 0.82, and moderately correlated with the NPI hallucinations score (rs = 0.42. Using an optimal cut-off score set according to the ROC analysis, and the pareidolia test differentiated DLB from AD with a sensitivity of 81% and a specificity of 92%.Our study suggests that the simplified version of the pareidolia test is a valid and reliable surrogate marker of visual hallucinations in DLB.

Decreased corticospinal excitability after the illusion of missing part of the arm

Directory of Open Access Journals (Sweden)

Konstantina eKilteni

2016-04-01

Full Text Available Previous studies on body ownership illusions have shown that under certain multimodal conditions, healthy people can experience artificial body-parts as if they were part of their own body, with direct physiological consequences for the real limb that gets ‘substituted’. In this study we wanted to assess (a whether healthy people can experience ‘missing’ a body-part through illusory ownership of an amputated virtual body, and (b whether this would cause corticospinal excitability changes in muscles associated with the ‘missing’ body-part. Forty right-handed participants saw a virtual body from a first person perspective but for half of them the virtual body was missing a part of its right arm. Single pulse transcranial magnetic stimulation was applied before and after the experiment to left and right motor cortices. Motor evoked potentials (MEPs were recorded from the first dorsal interosseous (FDI and the extensor digitorum communis (EDC of each hand. We found that the stronger the illusion of amputation and arm ownership, the more the reduction of MEP amplitudes of the EDC muscle for the contralateral sensorimotor cortex. In contrast, no association was found for the EDC amplitudes in the ipsilateral cortex and for the FDI amplitudes in both contralateral and ipsilateral cortices. Our study provides evidence that a short-term illusory perception of missing a body-part can trigger inhibitory effects on corticospinal pathways and importantly in the absence of any limb deafferentation or disuse.

The projected hand illusion: component structure in a community sample and association with demographics, cognition, and psychotic-like experiences.

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Graham, Kyran T; Martin-Iverson, Mathew T; Holmes, Nicholas P; Waters, Flavie A

2015-01-01

The projected hand illusion (PHI) is a variant of the rubber hand illusion (RHI), and both are commonly used to study mechanisms of self-perception. A questionnaire was developed by Longo et al. (2008) to measure qualitative changes in the RHI. Such psychometric analyses have not yet been conducted on the questionnaire for the PHI. The present study is an attempt to validate minor modifications of the questionnaire of Longo et al. to assess the PHI in a community sample (n = 48) and to determine the association with selected demographic (age, sex, years of education), cognitive (Digit Span), and clinical (psychotic-like experiences) variables. Principal components analysis on the questionnaire data extracted four components: Embodiment of "Other" Hand, Disembodiment of Own Hand, Deafference, and Agency-in both synchronous and asynchronous PHI conditions. Questions assessing "Embodiment" and "Agency" loaded onto orthogonal components. Greater illusion ratings were positively associated with being female, being younger, and having higher scores on psychotic-like experiences. There was no association with cognitive performance. Overall, this study confirmed that self-perception as measured with PHI is a multicomponent construct, similar in many respects to the RHI. The main difference lies in the separation of Embodiment and Agency into separate constructs, and this likely reflects the fact that the "live" image of the PHI presents a more realistic picture of the hand and of the stroking movements of the experimenter compared with the RHI.

The association of motor imagery and kinesthetic illusion prolongs the effect of transcranial direct current stimulation on corticospinal tract excitability.

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Kaneko, Fuminari; Shibata, Eriko; Hayami, Tatsuya; Nagahata, Keita; Aoyama, Toshiyuki

2016-04-15

A kinesthetic illusion induced by a visual stimulus (KI) can produce vivid kinesthetic perception. During KI, corticospinal tract excitability increases and results in the activation of cerebral networks. Transcranial direct current stimulation (tDCS) is emerging as an alternative potential therapeutic modality for a variety of neurological and psychiatric conditions, such that identifying factors that enhance the magnitude and duration of tDCS effects is currently a topic of great scientific interest. This study aimed to establish whether the combination of tDCS with KI and sensory-motor imagery (MI) induces larger and longer-lasting effects on the excitability of corticomotor pathways in healthy Japanese subjects. A total of 21 healthy male volunteers participated in this study. Four interventions were investigated in the first experiment: (1) anodal tDCS alone (tDCSa), (2) anodal tDCS with visually evoked kinesthetic illusion (tDCSa + KI), (3) anodal tDCS with motor imagery (tDCSa + MI), and (4) anodal tDCS with kinesthetic illusion and motor imagery (tDCSa + KIMI). In the second experiment, we added a sham tDCS intervention with kinesthetic illusion and motor imagery (sham + KIMI) as a control for the tDCSa + KIMI condition. Direct currents were applied to the right primary motor cortex. Corticospinal excitability was examined using transcranial magnetic stimulation of the area associated with the left first dorsal interosseous. In the first experiment, corticomotor excitability was sustained for at least 30 min following tDCSa + KIMI (p < 0.01). The effect of tDCSa + KIMI on corticomotor excitability was greater and longer-lasting than that achieved in all other conditions. In the second experiment, significant effects were not achieved following sham + KIMI. Our results suggest that tDCSa + KIMI has a greater therapeutic potential than tDCS alone for inducing higher excitability of the corticospinal tract. The observed

Development of Right-hemispheric Dominance of Inferior Parietal Lobule in Proprioceptive Illusion Task.

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Naito, Eiichi; Morita, Tomoyo; Saito, Daisuke N; Ban, Midori; Shimada, Koji; Okamoto, Yuko; Kosaka, Hirotaka; Okazawa, Hidehiko; Asada, Minoru

2017-11-01

Functional lateralization can be an indicator of brain maturation. We have consistently shown that, in the adult brain, proprioceptive processing of muscle spindle afferents generating illusory movement of the right hand activates inferior frontoparietal cortical regions in a right-side dominant manner in addition to the cerebrocerebellar motor network. Here we provide novel evidence regarding the development of the right-dominant use of the inferior frontoparietal cortical regions in humans using this task. We studied brain activity using functional magnetic resonance imaging while 60 right-handed blindfolded healthy children (8-11 years), adolescents (12-15 years), and young adults (18-23 years) (20 per group) experienced the illusion. Adult-like right-dominant use of the inferior parietal lobule (IPL) was observed in adolescents, while children used the IPL bilaterally. In contrast, adult-like lateralized cerebrocerebellar motor activation patterns were already observable in children. The right-side dominance progresses during adolescence along with the suppression of the left-sided IPL activity that emerges during childhood. Therefore, the neuronal processing implemented in the adult's right IPL during the proprioceptive illusion task is likely mediated bilaterally during childhood, and then becomes right-lateralized during adolescence at a substantially later time than the lateralized use of the cerebrocerebellar motor system for kinesthetic processing. © The Author 2017. Published by Oxford University Press.

What Factors Underlie Associative and Categorical Memory Illusions? The Roles of Backward Associative Strength and Interitem Connectivity

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Knott, Lauren M.; Dewhurst, Stephen A.; Howe, Mark L.

2012-01-01

Factors that affect categorical and associative false memory illusions were investigated in 2 experiments. In Experiment 1, backward associative strength (BAS) from the list word to the critical lure and interitem connectivity were manipulated in Deese-Roediger-McDermott (DRM) and category list types. For both recall and recognition tasks, the…

On the role of spatial phase and phase correlation in vision, illusion, and cognition

OpenAIRE

Gladilin, Evgeny; Eils, Roland

2015-01-01

Numerous findings indicate that spatial phase bears an important cognitive information. Distortion of phase affects topology of edge structures and makes images unrecognizable. In turn, appropriately phase-structured patterns give rise to various illusions of virtual image content and apparent motion. Despite a large body of phenomenological evidence not much is known yet about the role of phase information in neural mechanisms of visual perception and cognition. Here, we are concerned with a...

On the role of spatial phase and phase correlation in vision, illusion and cognition

OpenAIRE

Evgeny eGladilin; Roland eEils; Roland eEils

2015-01-01

Numerous findings indicate that spatial phase bears an important cognitive information. Distortion of phase affects topology of edge structures and makes images unrecognizable. In turn, appropriately phase-structured patterns give rise to various illusions of virtual image content and apparent motion. Despite a large body of phenomenological evidence not much is known yet about the role of phase information in neural mechanisms of visual perception and cognition. Here, we are concerned with a...

Creating illusions of past encounter through brief exposure.

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Brown, Alan S; Marsh, Elizabeth J

2009-05-01

Titchener (1928) suggested that briefly glancing at a scene could make it appear strangely familiar when it was fully processed moments later. The closest laboratory demonstration used words as stimuli, and showed that briefly glancing at a to-be-judged word increased the subject's belief that it had been presented in an earlier study list (Jacoby & Whitehouse, 1989). We evaluated whether a hasty glance could elicit a false belief in a prior encounter, from a time and place outside of the experiment. This goal precluded using word stimuli, so we had subjects evaluate unfamiliar symbols. Each symbol was preceded by a brief exposure to an identical symbol, a different symbol, or no symbol. A brief glance at an identical symbol increased attributions to preexperimental experience, relative to a glance at a different symbol or no symbol, providing a possible mechanism for common illusions of false recognition.

Humans, but not animals, perceive the thermal grill illusion as painful.

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Boettger, Michael K; Ditze, Günter; Bär, Karl-Juergen; Krüdewagen, Eva Maria; Schaible, Hans-Georg

2016-10-15

Simultaneous presentation of alternating innocuous warm and cold stimuli induces in most humans a painful sensation called thermal grill illusion (TGI). Here, pain is elicited although nociceptors are not activated. Upon back-translation of behavioural correlates from humans to animals, we found that neither cats nor rodents show adverse reactions when exposed to TGI stimulation. These results question that a TGI observed as a pain-related change in behaviour can be elicited in animals. While distinct neuronal patterns as previously reported may be measurable in animals upon TGI stimulation, their translational meaning towards the sensation elicited in humans is unclear. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrophysiological evidence for differences between fusion and combination illusions in audiovisual speech perception

DEFF Research Database (Denmark)

Baart, Martijn; Lindborg, Alma Cornelia; Andersen, Tobias S

2017-01-01

Incongruent audiovisual speech stimuli can lead to perceptual illusions such as fusions or combinations. Here, we investigated the underlying audiovisual integration process by measuring ERPs. We observed that visual speech-induced suppression of P2 amplitude (which is generally taken as a measure...... of audiovisual integration) for fusions was comparable to suppression obtained with fully congruent stimuli, whereas P2 suppression for combinations was larger. We argue that these effects arise because the phonetic incongruency is solved differently for both types of stimuli. This article is protected...

Perceptual organization reconsidered in the light of the watercolor illusion: The problem of perception of holes and the object-hole effect.

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Pinna, Baingio; Tanca, Maria

2008-05-23

The watercolor illusion is a long-range color assimilation (coloration effect) imparting a figure-ground segregation (figural effect) across large enclosed areas (B. Pinna, 1987; B. Pinna, G. Brelstaff, & L. Spillmann, 2001; B. Pinna, L. Spillmann, & J. S. Werner, 2003; B. Pinna, J. S. Werner, & L. Spillmann, 2003). The watercolored figure has a very poorly reversible or univocal figure-ground segregation and strongly enhances the unilateral belongingness of the boundaries (E. Rubin, 1915), a principle stating that the boundaries belong only to the figure and not to the background. The figural effect determines grouping and figure-ground segregation more strongly than the well-known Gestalt principles. Under watercolor conditions both the figure and the background assume new properties becoming respectively bulging object and hole both with a 3-D volumetric appearance (object-hole effect). Our purposes were: (i) to demonstrate that the hole induced by the watercolor illusion has unique figural properties comparable to those of the object and not present in the background induced by the known figure-ground principles; (ii) to demonstrate a dissociation of the object-hole effect from the coloration one; (iii) to demonstrate that the object-hole effect depends on a new principle. This was psychophysically tested by weakening (ungrouping) the whole figural organization of the watercolor illusion, i.e. by imparting motion to only some components of a stimulus, while other components remain stationary. The results showed that (i) subjects perceived moving holes more strongly than moving figures or objects enlarging and shrinking. (ii) Paradoxically, moving holes appear more as figures than the bulging surfaces. (iii) When motion was imparted to components that while stationary were perceived as objects, their figurality is further enhanced (summation effect). (iv) When object-hole and coloration effects were dissociated no significant difference compared to illusory

Reports of wins and risk taking: an investigation of the mediating effect of the illusion of control.

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Martinez, Frédéric; Le Floch, Valérie; Gaffié, Bernard; Villejoubert, Gaëlle

2011-06-01

Two experiments examined the relationships between the knowledge that another person has won in a gamble, the illusion of control and risk taking. Participants played a computer-simulated French roulette game individually. Before playing, some participants learnt that another person won a large amount of money. Results from a first experiment (n = 24) validated a causal model where the knowledge of another person's win increased the illusion of control, measured with betting times, expectancy and self-reports on scales, which in turn encourages risk taking. In the second experiment (n = 36), some participants were told the previous player acknowledged the win to be fortuitous. The suppression of the belief that the previous winner had himself exerted control over the outcome resulted in lower rates of risk-taking behaviors. This suggests that it was not the knowledge of another person's win in itself that increased risk taking, but rather, the belief that the other person had some control over the gamble's outcome. Theoretical implications for the study of social mechanisms involved in gambling behavior are discussed.

Visual illusions and plate design: the effects of plate rim widths and rim coloring on perceived food portion size.

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McClain, A D; van den Bos, W; Matheson, D; Desai, M; McClure, S M; Robinson, T N

2014-05-01

The Delboeuf Illusion affects perceptions of the relative sizes of concentric shapes. This study was designed to extend research on the application of the Delboeuf illusion to food on a plate by testing whether a plate's rim width and coloring influence perceptual bias to affect perceived food portion size. Within-subjects experimental design. Experiment 1 tested the effect of rim width on perceived food portion size. Experiment 2 tested the effect of rim coloring on perceived food portion size. In both experiments, participants observed a series of photographic images of paired, side-by-side plates varying in designs and amounts of food. From each pair, participants were asked to select the plate that contained more food. Multilevel logistic regression examined the effects of rim width and coloring on perceived food portion size. Experiment 1: participants overestimated the diameter of food portions by 5% and the visual area of food portions by 10% on plates with wider rims compared with plates with very thin rims (Pfood portion sizes. Experiment 2: participants overestimated the diameter of food portions by 1.5% and the visual area of food portions by 3% on plates with rim coloring compared with plates with no coloring (P=0.01). The effect of rim coloring was greater with smaller food portion sizes. The Delboeuf illusion applies to food on a plate. Participants overestimated food portion size on plates with wider and colored rims. These findings may help design plates to influence perceptions of food portion sizes.

Increased functional connectivity between superior colliculus and brain regions implicated in bodily self-consciousness during the rubber hand illusion.

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Olivé, Isadora; Tempelmann, Claus; Berthoz, Alain; Heinze, Hans-Joachim

2015-02-01

Bodily self-consciousness refers to bodily processes operating at personal, peripersonal, and extrapersonal spatial dimensions. Although the neural underpinnings of representations of personal and peripersonal space associated with bodily self-consciousness were thoroughly investigated, relatively few is known about the neural underpinnings of representations of extrapersonal space relevant for bodily self-consciousness. In the search to unravel brain structures generating a representation of the extrapersonal space relevant for bodily self-consciousness, we developed a functional magnetic resonance imaging (fMRI) study to investigate the implication of the superior colliculus (SC) in bodily illusions, and more specifically in the rubber hand illusion (RHi), which constitutes an established paradigm to study the neural underpinnings of bodily self-consciousness. We observed activation of the colliculus ipsilateral to the manipulated hand associated with eliciting of RHi. A generalized form of context-dependent psychophysiological interaction analysis unravelled increased illusion-dependent functional connectivity between the SC and some of the main brain areas previously involved in bodily self-consciousness: right temporoparietal junction (rTPJ), bilateral ventral premotor cortex (vPM), and bilateral postcentral gyrus. We hypothesize that the collicular map of the extrapersonal space interacts with maps of the peripersonal and personal space generated at rTPJ, vPM and the postcentral gyrus, producing a unified representation of space that is relevant for bodily self-consciousness. We suggest that processes of multisensory integration of bodily-related sensory inputs located in this unified representation of space constitute one main factor underpinning emergence of bodily self-consciousness. © 2014 Wiley Periodicals, Inc.

There is something inauthentic in each original: a very brief study of the illusion from the movie “The Best Offer”of Giuseppe Tornatore

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Rogério de Almeida

2016-06-01

Full Text Available Based on the film The Best Offer (LA MIGLIORE OFFERTA, 2013, by Giuseppe Tornatore, this article proposes a reflection on the illusion of the double expressed by the original-copy dichotomy. After a brief introduction of how this dichotomy has become paradigmatic in the western thought, we point out the philosophy of Clément Rosset to discuss the central theme of the film: “there is always something authentic in each copy”. We argue, finally, that the illusion is not only to transform something into two, but also in the deluded's unwillingness to approve a reality that is impossible to duplicate.

Memory plays tricks on me: perceptual bias induced by memory reactivated size in Ebbinghaus illusion.

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Rey, Amandine E; Vallet, Guillaume T; Riou, Benoit; Lesourd, Mathieu; Versace, Rémy

2015-10-01

The relationship between perceptual and memory processing is at the core of cognition. Growing evidence suggests reciprocal influences between them so that memory features should lead to an actual perceptual bias. In the present study, we investigate the reciprocal influence of perceptual and memory processing by further adapting the Ebbinghaus illusion and tested it in a psychophysical design. In a 2AFC (two-alternative forced choice) paradigm, the perceptual bias in the Ebbinghaus illusion was induced by a physical size (Experiment 1) or a memory reactivated size of the inducers (Experiment 2, the size was reactivated thanks to a color-size association). One test disk was presented on the left of the screen and was surrounded by six inducers with a large or small (perceptual or reactivated) size. The test disk varied in size and participants were asked to indicate whether this test disk was smaller or larger than a reference disk presented on the right of the screen (the reference disk was invariant in size). Participants' responses were influenced by the size of the inducers for the perceptual and the reactivated size of the inducers. These results provide new evidence for the influence of memory on perception in a psychophysics paradigm. Published by Elsevier B.V.

Investigating the illusion of control in mildly depressed and nondepressed individuals during video-poker play.

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Dannewitz, Holly; Weatherly, Jeffrey N

2007-05-01

Cognitive fallacies, such as the illusion of control, and psychological disorders, such as depression, may perpetuate gambling and thus contribute to problem gambling (e.g., R. Ladouceur, C. Sylvan, C. Boutin, & C. Doucet, 2002). Gender differences may exist across these variables (e.g., N. M. Petry, 2005). The authors investigated these possibilities by recruiting mildly depressed and nondepressed individuals to play jacks or better, 5-card draw, video poker. Across three poker sessions, participants were given (a) no choice of which cards to play, (b) information on the best cards to play but control over which cards were played, or (c) no information and complete control over which cards were played. The total amount of money gambled increased as control over the game decreased, but this result correlated with an increase in the rate of play. Depressed and nondepressed participants did not differ in how they gambled, but men gambled significantly more and sometimes made more mistakes during play than did women. These results question the role of the illusion of control and depression in perpetuating gambling. They also suggest that providing players information about which cards to play may indirectly promote gambling and provide insight as to why men are more prone to suffer from gambling problems than are women.

Multisensory integration across exteroceptive and interoceptive domains modulates self-experience in the rubber-hand illusion.

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Suzuki, Keisuke; Garfinkel, Sarah N; Critchley, Hugo D; Seth, Anil K

2013-11-01

Identifying with a body is central to being a conscious self. The now classic "rubber hand illusion" demonstrates that the experience of body-ownership can be modulated by manipulating the timing of exteroceptive (visual and tactile) body-related feedback. Moreover, the strength of this modulation is related to individual differences in sensitivity to internal bodily signals (interoception). However the interaction of exteroceptive and interoceptive signals in determining the experience of body-ownership within an individual remains poorly understood. Here, we demonstrate that this depends on the online integration of exteroceptive and interoceptive signals by implementing an innovative "cardiac rubber hand illusion" that combined computer-generated augmented-reality with feedback of interoceptive (cardiac) information. We show that both subjective and objective measures of virtual-hand ownership are enhanced by cardio-visual feedback in-time with the actual heartbeat, as compared to asynchronous feedback. We further show that these measures correlate with individual differences in interoceptive sensitivity, and are also modulated by the integration of proprioceptive signals instantiated using real-time visual remapping of finger movements to the virtual hand. Our results demonstrate that interoceptive signals directly influence the experience of body ownership via multisensory integration, and they lend support to models of conscious selfhood based on interoceptive predictive coding. © 2013 Elsevier Ltd. All rights reserved.

Optical coherence tomography: beware of optical illusions

NARCIS (Netherlands)

Kok, P.H.B.

2014-01-01

De retina, het netvlies, is een van meest intrigerende onderdelen van het oog. In tegenstelling tot menig ander medisch specialist heeft de oogarts de mogelijkheid in het orgaan van zijn of haar specialisme te kijken. Met behulp van een oftalmoscoop kan het netvlies non-invasief bestudeerd worden,

PENGARUH ILLUSIONS OF CONTROL, OVERCONFIDENCE DAN EMOTION TERHADAP PENGAMBILAN KEPUTUSAN INVESTASI PADA INVESTOR DI YOGYAKARTA

OpenAIRE

Kartini, Kartini; Nugraha, Nuris Firmansyah

2015-01-01

Nowadays Investors often make investment decision irrationally. The decision is often based on their judgment that is far away from rational assumption. When investors face risky situa-tion, there are some objectivities, emotions, and other psychological factors that usually ef-fect their decision making. This purpose of study is to examine the effect of illusions of control, risk tolerance, overconfidence and emotion on investment decision making among investors in yogyakarta. Sample of this...

Is This Hand for Real? Attenuation of the Rubber Hand Illusion by Transcranial Magnetic Stimulation over the Inferior Parietal Lobule

NARCIS (Netherlands)

Kammers, M.P.M.; Verhagen, L.; Dijkerman, H.C.; Hogendoorn, H.; Vignemont, F. de; Schutter, D.J.L.G.

2009-01-01

In the rubber hand illusion (RHI), participants incorporate a rubber hand into a mental representation of one's body. This deceptive feeling of ownership is accompanied by recalibration of the perceived position of the participant's real hand toward the rubber hand. Neuroimaging data suggest

On the relationship between optical variability, visual saliency, and eye fixations: a computational approach.

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Garcia-Diaz, Antón; Leborán, Víctor; Fdez-Vidal, Xosé R; Pardo, Xosé M

2012-06-12

A hierarchical definition of optical variability is proposed that links physical magnitudes to visual saliency and yields a more reductionist interpretation than previous approaches. This definition is shown to be grounded on the classical efficient coding hypothesis. Moreover, we propose that a major goal of contextual adaptation mechanisms is to ensure the invariance of the behavior that the contribution of an image point to optical variability elicits in the visual system. This hypothesis and the necessary assumptions are tested through the comparison with human fixations and state-of-the-art approaches to saliency in three open access eye-tracking datasets, including one devoted to images with faces, as well as in a novel experiment using hyperspectral representations of surface reflectance. The results on faces yield a significant reduction of the potential strength of semantic influences compared to previous works. The results on hyperspectral images support the assumptions to estimate optical variability. As well, the proposed approach explains quantitative results related to a visual illusion observed for images of corners, which does not involve eye movements.

The neuronal correlates of mirror illusion in children with spastic hemiparesis: a study with functional magnetic resonance imaging.

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Weisstanner, Christian; Saxer, Stefanie; Wiest, Roland; Kaelin-Lang, Alain; Newman, Christopher J; Steinlin, Maja; Grunt, Sebastian

2017-03-21

To investigate the neuronal activation pattern underlying the effects of mirror illusion in children/adolescents with normal motor development and in children/adolescents with hemiparesis and preserved contralateral corticospinal organisation. The type of cortical reorganisation was classified according to results of transcranial magnetic stimulation. Only subjects with congenital lesions and physiological contralateral cortical reorganisation were included. Functional magnetic resonance imaging was performed to investigate neuronal activation patterns with and without a mirror box. Each test consisted of a unimanual and a bimanual motor task. Seven children/adolescents with congenital hemiparesis (10-20 years old, three boys and four girls) and seven healthy subjects (8-17 years old, four boys and three girls) participated in this study. In the bimanual experiment, children with hemiparesis showed a significant effect of the mirror illusion (phemiparesis leads to activation of brain areas involved in visual conflict detection and cognitive control to resolve this conflict. This effect is observed only in bimanual training. We consider that for mirror therapy in children and adolescents with hemiparesis a bimanual approach is more suitable than a unimanual approach.

The Mirror Illusion Increases Motor Cortex Excitability in Children With and Without Hemiparesis.

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Grunt, Sebastian; Newman, Christopher J; Saxer, Stefanie; Steinlin, Maja; Weisstanner, Christian; Kaelin-Lang, Alain

2017-03-01

Mirror therapy provides a visual illusion of a normal moving limb by using the mirror reflection of the unaffected arm instead of viewing the paretic limb and is used in rehabilitation to improve hand function. Little is known about the mechanism underlying its effect in children with hemiparesis. To investigate the effect of the mirror illusion (MI) on the excitability of the primary motor cortex (M1) in children and adolescents. Twelve patients with hemiparesis (10-20 years) and 8 typically developing subjects (8-17 years) participated. Corticospinal reorganization was classified as contralateral (projection from contralateral hemisphere to affected hand) or ipsilateral (projection from ipsilateral hemisphere to affected hand). M1 excitability of the hemisphere projecting to the affected (nondominant in typically developing subjects) hand was obtained during 2 different conditions using single-pulse transcranial magnetic stimulation (TMS). Each condition (without/with mirror) consisted of a unimanual and a bimanual task. Motor-evoked potentials (MEPs) were recorded from the abductor pollicis brevis and flexor digitorum superficialis muscles. MEP amplitudes were significantly increased during the mirror condition ( P = .005) in typically developing subjects and in patients with contralateral reorganization. No significant effect of MI was found in subjects with ipsilateral reorganization. MI increased M1 excitability during active movements only. This increase was not correlated to hand function. MI increases the excitability of M1 in hemiparetic patients with contralateral corticospinal organization and in typically developing subjects. This finding provides neurophysiological evidence supporting the application of mirror therapy in selected children and adolescents with hemiparesis.

On the (elusive) role of oral motor-movements in fluency-based memory illusions.

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Westerman, Deanne L; Klin, Celia M; Lanska, Meredith

2015-07-01

It is well established that the ease with which a stimulus is processed affects many different types of evaluative judgments. Recently, it has been proposed that for verbal stimuli the effect of fluency on such judgments is mediated by the muscles that are involved in speech (Topolinski & Strack, 2009, 2010). Evidence for this claim can be found in studies that have shown that fluency effects are eliminated if such judgments are made while these muscles are otherwise engaged (such as while chewing gum or eating). Additional research has found that oral-motor tasks block familiarity-based responding on recognition memory tasks (Topolinski, 2012). The current study investigated the effect of an oral-motor task on recognition memory. Of particular interest was whether the fluency-blocking effects of an oral-motor task would extend to fluency-based illusions of recognition memory. Although we found robust fluency-based illusions of familiarity, we did not find that the effects were modulated by the nature of the concurrent task (gum-chewing vs. a manual-motor task). Moreover, we found no evidence that oral-motor tasks affected recognition more generally, nor did we find that an oral-motor task modulated affective ratings to repeated stimuli. We were also unable to replicate the finding that an oral-motor task blocks the false fame effect (Topolinski & Strack, 2010). These results call into question the assertion that oral-motor movements mediate fluency effects in recognition memory and other evaluative judgments. (c) 2015 APA, all rights reserved.

A nickel ain't worth a dime anymore: the illusion of money and the rapid encoding of its true value.

Directory of Open Access Journals (Sweden)

Rongjun Yu

Full Text Available People often evaluate money based on its face value and overlook its real purchasing power, known as the money illusion. For example, the same 100 Chinese Yuan can buy many more goods in Tibet than in Beijing, but such difference in buying power is usually underestimated. Using event related potential combined with a gambling task, we sought to investigate the encoding of both the real value and the face value of money in the human brain. We found that the self-reported pleasantness of outcomes was modulated by both values. The feedback related negativity (FRN, which peaks around 250ms after feedback and is believed to be generated in the anterior cingulate cortex (ACC, was only modulated by the true value but not the face value of money. We conclude that the real value of money is rapidly encoded in the human brain even when participants exhibit the money illusion at the behavioral level.

Electrophysiological evidence for differences between fusion and combination illusions in audiovisual speech perception.

Science.gov (United States)

Baart, Martijn; Lindborg, Alma; Andersen, Tobias S

2017-11-01

Incongruent audiovisual speech stimuli can lead to perceptual illusions such as fusions or combinations. Here, we investigated the underlying audiovisual integration process by measuring ERPs. We observed that visual speech-induced suppression of P2 amplitude (which is generally taken as a measure of audiovisual integration) for fusions was similar to suppression obtained with fully congruent stimuli, whereas P2 suppression for combinations was larger. We argue that these effects arise because the phonetic incongruency is solved differently for both types of stimuli. © 2017 The Authors. European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

When Passive Feels Active--Delusion-Proneness Alters Self-Recognition in the Moving Rubber Hand Illusion.

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Louzolo, Anaïs; Kalckert, Andreas; Petrovic, Predrag

2015-01-01

Psychotic patients have problems with bodily self-recognition such as the experience of self-produced actions (sense of agency) and the perception of the body as their own (sense of ownership). While it has been shown that such impairments in psychotic patients can be explained by hypersalient processing of external sensory input it has also been suggested that they lack normal efference copy in voluntary action. However, it is not known how problems with motor predictions like efference copy contribute to impaired sense of agency and ownership in psychosis or psychosis-related states. We used a rubber hand illusion based on finger movements and measured sense of agency and ownership to compute a bodily self-recognition score in delusion-proneness (indexed by Peters' Delusion Inventory - PDI). A group of healthy subjects (n=71) experienced active movements (involving motor predictions) or passive movements (lacking motor predictions). We observed a highly significant correlation between delusion-proneness and self-recognition in the passive conditions, while no such effect was observed in the active conditions. This was seen for both ownership and agency scores. The result suggests that delusion-proneness is associated with hypersalient external input in passive conditions, resulting in an abnormal experience of the illusion. We hypothesize that this effect is not present in the active condition because deficient motor predictions counteract hypersalience in psychosis proneness.

Subjective, behavioral, and physiological responses to the rubber hand illusion do not vary with age in the adult phase.

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Palomo, Priscila; Borrego, Adrián; Cebolla, Ausiàs; Llorens, Roberto; Demarzo, Marcelo; Baños, Rosa M

2018-02-01

The Rubber Hand Illusion (RHI) is a perceptual illusion that enables integration of artificial limbs into the body representation through combined multisensory integration. Most previous studies investigating the RHI have involved young healthy adults within a very narrow age range (typically 20-30 years old). The purpose of this paper was to determine the influence of age on the RHI. The RHI was performed on 93 healthy adults classified into three groups of age (20-35 years old, N = 41; 36-60 years old, N = 28; and 61-80 years old, N = 24), and its effects were measured with subjective (Embodiment of Rubber Hand Questionnaire), behavioral (proprioceptive drift), and physiological (changes in skin temperature and conductance) measures. There were neither significant differences among groups in any response, nor significant covariability or correlation between age and other measures (but for skin temperature), which suggests that the RHI elicits similar responses across different age groups in the adult phase. Copyright © 2017 Elsevier Inc. All rights reserved.

The Rubber Hand Illusion in Children with Autism Spectrum Disorders: Delayed Influence of Combined Tactile and Visual Input on Proprioception

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Cascio, Carissa J.; Foss-Feig, Jennifer H.; Burnette, Courtney P.; Heacock, Jessica L.; Cosby, Akua A.

2012-01-01

In the rubber hand illusion, perceived hand ownership can be transferred to a rubber hand after synchronous visual and tactile stimulation. Perceived body ownership and self-other relation are foundational for development of self-awareness, imitation, and empathy, which are all affected in autism spectrum disorders (ASD). We examined the rubber…

The development of the illusion of control and sense of agency in 7- to-12-year old children and adults

NARCIS (Netherlands)

van Elk, M.; Rutjens, B.T.; van der Pligt, J.

2015-01-01

The illusion of control can be defined as the erroneous belief that one’s actions cause a specific outcome, whereas sense of agency refers to the subjective feeling of authorship over one’s actions. In the present study we investigated the development of illusory control and sense of agency. A novel

About the Eye

Medline Plus

Full Text Available ... Stuff Cool Eye Tricks Links to More Information Optical Illusions Printables ... Optic nerve (OP-tic nurv) is the bundle of more than 1 million nerve fibers that carry visual messages from the retina to ...

Optical modelling of photoluminescence emitted by thin doped films

International Nuclear Information System (INIS)

Pigeat, P.; Easwarakhanthan, T.; Briancon, J.L.; Rinnert, H.

2011-01-01

Photoluminescence (PL) spectra emitted by doped films are deformed owing to film thickness-dependent wave interference. This hampers knowing well their PL generating mechanisms as well as designing photonic devices with suitable geometries that improve their PL efficiency. We develop in this paper an energy model for PL emitted by doped films considering the interaction between the wavelength-differing incident standing and emitted waves, their energy transfer in-between, and the interferences undergone by both. The film optical constants are estimated fitting the model to the measured PL. This simple model has thus allowed us to interpret the evolution of PL emitted by Er-doped AlN films prepared on Si substrates by reactive magnetron sputtering. The shapes, the amplitudes, and the illusive sub-spectral features of the PL spectra depend essentially on the film thickness. The model further predicts high sensitivity for PL emitted by non-homogenously doped stacked-films to incident light wavelengths and film-thickness variations. This property has potential applications in tracking wavelength variations and in measuring physical quantities producing thickness variations. This model may be used to optimise PL efficiency of photonic devices through different film geometries and optical properties.

National Science Resources Center Project to Improve Science Teaching in Elementary Schools. Appendix C. Elementary Science Information Database

Science.gov (United States)

1988-12-01

individual particles. They mix the powders with water and perform tests with heat, iodine, and vinegar in order to gain additional information about the...illusions ; light ; fermentation ; chromatography ; moon ; astronomy AN SCIENCE - A PROCESS APPROACH, PART G focuses on experimentation, incorporating all...skills ; flowers plants astronomy ; animals ; sensory perception ; vision ; optical illusions ; eyes ; density ; viscosity ; fermentation ; moon

Effect of kinesthetic illusion induced by visual stimulation on muscular output function after short-term immobilization.

Science.gov (United States)

Inada, Toru; Kaneko, Fuminari; Hayami, Tatsuya

2016-04-01

Kinesthetic illusions by visual stimulation (KiNVIS) enhances corticomotor excitability and activates motor association areas. The purpose of this study was to investigate the effect of KiNVIS induction on muscular output function after short-term immobilization. Thirty subjects were assigned to 3 groups: an immobilization group, with the left hand immobilized for 12h (immobilization period); an illusion group, with the left hand immobilized and additionally subjected to KiNVIS of the immobilized part during the immobilization period; and a control group with no manipulation. The maximum voluntary contraction (MVC), fluctuation of force (force fluctuation) during a force modulation task, and twitch force were measured both before (pre-test) and after (post-test) the immobilization period. Data were analyzed by performing two-way (TIME×GROUP) repeated measures ANOVA. The MVC decreased in the immobilization group only (pre-test; 37.8±6.1N, post-test; 32.8±6.9N, p<0.0005) after the immobilization period. The force fluctuation increased only in the immobilization group (pre-test; 2.19±0.54%, post-test; 2.78±0.87%, p=0.007) after the immobilization period. These results demonstrate that induction of KiNVIS prevents negative effect on MVC and force fluctuation after 12h of immobilization. Copyright © 2016 Elsevier Ltd. All rights reserved.

The human touch: skin temperature during the rubber hand illusion in manual and automated stroking procedures.

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Marieke Rohde

Full Text Available A difference in skin temperature between the hands has been identified as a physiological correlate of the rubber hand illusion (RHI. The RHI is an illusion of body ownership, where participants perceive body ownership over a rubber hand if they see it being stroked in synchrony with their own occluded hand. The current study set out to replicate this result, i.e., psychologically induced cooling of the stimulated hand using an automated stroking paradigm, where stimulation was delivered by a robot arm (PHANToM(TM force-feedback device. After we found no evidence for hand cooling in two experiments using this automated procedure, we reverted to a manual stroking paradigm, which is closer to the one employed in the study that first produced this effect. With this procedure, we observed a relative cooling of the stimulated hand in both the experimental and the control condition. The subjective experience of ownership, as rated by the participants, by contrast, was strictly linked to synchronous stroking in all three experiments. This implies that hand-cooling is not a strict correlate of the subjective feeling of hand ownership in the RHI. Factors associated with the differences between the two designs (differences in pressure of tactile stimulation, presence of another person that were thus far considered irrelevant to the RHI appear to play a role in bringing about this temperature effect.

The development of multisensory body representation and awareness continues to 10 years of age: Evidence from the rubber hand illusion.

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Cowie, Dorothy; Sterling, Samantha; Bremner, Andrew J

2016-02-01

Recent research using the "rubber hand illusion" shows that the multisensory processes underlying body representations are markedly different in children of 4 to 9years and adults. In representing the position of their own hand in external space, children of this age rely more on the sight of the hand, and less on its proprioceptively felt position, than adults do. The current study investigated when during later childhood the balance between visual and proprioceptive inputs reaches an adult-like weighting. After inducing the rubber hand illusion in 10- to 13-year-olds, we asked participants to point, with eyes closed, to the perceived position of their hand. We found that pointing responses reached adult levels at 10 to 11years, showing that at this age children perceive hand location using an adult-like balance of sensory cues. We conclude that the multisensory foundations of the bodily self undergo a protracted period of development through early and mid-childhood, reaching an adult state by 10 to 11years. Copyright © 2015 Elsevier Inc. All rights reserved.

Learning Empathy Through Virtual Reality: Multiple Strategies for Training Empathy-Related Abilities Using Body Ownership Illusions in Embodied Virtual Reality

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Philippe Bertrand

2018-03-01

Full Text Available Several disciplines have investigated the interconnected empathic abilities behind the proverb “to walk a mile in someone else’s shoes” to determine how the presence, and absence, of empathy-related phenomena affect prosocial behavior and intergroup relations. Empathy enables us to learn from others’ pain and to know when to offer support. Similarly, virtual reality (VR appears to allow individuals to step into someone else’s shoes, through a perceptual illusion called embodiment, or the body ownership illusion. Considering these perspectives, we propose a theoretical analysis of different mechanisms of empathic practices in order to define a possible framework for the design of empathic training in VR. This is not intended to be an extensive review of all types of practices, but an exploration of empathy and empathy-related phenomena. Empathy-related training practices are analyzed and categorized. We also identify different variables used by pioneer studies in VR to promote empathy-related responses. Finally, we propose strategies for using embodied VR technology to train specific empathy-related abilities.

Owning the body in the mirror: The effect of visual perspective and mirror view on the full-body illusion.

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Preston, Catherine; Kuper-Smith, Benjamin J; Ehrsson, Henrik H

2015-12-17

Mirrors allow us to view our own body from a third-person (observer) perspective. However, how viewing ourselves through a mirror affects central body representations compared with true third-person perspective is not fully understood. Across a series of experiments, multisensory full-body illusions were used to modulate feelings of ownership over a mannequin body that was viewed from a third-person perspective through a mirror, from a third-person perspective without a mirror, and from a first-person perspective. In contrast to non-mirror third-person perspective, synchronously touching the participant's actual body and the mannequin body viewed in the mirror elicited strong feelings of ownership over the mannequin and increased physiological responses to the mannequin being threatened compared to the equivalent asynchronous (non-ownership) control condition. Subjective reports of ownership viewing the mannequin through a mirror were also statistically equivalent to those following the first-person perspective illusion. These findings suggest that mirrors have a special role for viewing the self. The results also support the importance of egocentric reference frames for body ownership and suggest that mirror reflections of one's own body are related to peripersonal space, which enables updating of central body representations.

The phenomenal dissociation between coloration and object-hole effects in the watercolor illusion.

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Tanca, Maria; Pinna, Baingio

2008-01-01

The watercolor illusion is a color spreading effect at long-range diffusing from a thin colored contour juxtaposed to a chromatic one of higher contrast and a object-hole effect across a large area (Pinna, 1987; Pinna et al., 2001, 2003; Pinna & Reeves, 2006). The watercolored figure appears evenly colored by an opaque light veil of chromatic tint (coloration effect), with a clear surface color property spreading from the lighter contour. At the same time, the watercolored figure manifests a strong figure-ground organization and a solid figural appearance comparable to a bas-relief illuminated from the top (object-hole effect). It appears similar to a rounded surface segregated in depth, which extends out from the flat surface. The complementary region appears as a hole or empty space. The phenomenal properties of coloration and object-hole effects raise some questions. Can the two effects be considered relatively independent? Under what conditions can a possible dissociation occur? How does the dissociation of one effect, say the coloration, influence the object-hole effect and vice versa? To answer these questions two new effects related to the watercolor illusion were psychophysically studied: (1) the "uneven watercolor," based on a modified watercolor figure without volumetric and three-dimensional properties but with a strong coloration effect and (2) the "watercolor surface capture," where oblique lines within a watercolor figure appear bulging, curved in depth and segregated from those that are perceived as placed in the background or perceived through holes. The results of two experiments suggest that the coloration effect can be dissociated from the object-hole one. These results are discussed in the light of a simple summation hypothesis of the underlying effects composing the whole figurality. This hypothesis can suggest further investigation both in the phenomenal and in the neurophysiological domain.

Effects of Short-Term Inpatient Treatment on Sensitivity to a Size Contrast Illusion in First-Episode Psychosis and Multiple-Episode Schizophrenia

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Steven M Silverstein

2013-07-01

Full Text Available Introduction: In the Ebbinghaus illusion, a shape appears larger than its actual size when surrounded by small shapes and smaller than its actual size when surrounded by large shapes. Resistance to this illusion has been previously reported in schizophrenia, and linked to disorganized symptoms and poorer prognosis in cross-sectional studies. It is unclear, however, when in the course of illness this resistance first emerges or how it varies longitudinally with illness phase. Method: First-episode psychosis patients, multiple-episode schizophrenia patients and healthy controls completed a psychophysical task at two different time points, corresponding to hospital admission and discharge for patients. The task required judging the relative size of two circles centered on either side of the screen. Targets were presented without context (baseline, or were surrounded by shapes that made the size judgment harder or easier (misleading and helpful contexts, respectively. Context sensitivity was operationalized as improvement relative to baseline in the helpful condition minus the amount of decrement (relative to baseline in the misleading condition. Results: At admission, context sensitivity was lower in the multiple-episode group than in the other groups, and was marginally less in the first episode than in the control group. In addition, schizophrenia patients were significantly more and less accurate than the other groups in the misleading and helpful conditions, respectively. At discharge, all groups exhibited similar context sensitivity. Poorer context sensitivity was related to higher levels of disorganized symptoms, and lower level of depression, excitement, and positive symptoms. Discussion: Resistance to the Ebbinghaus illusion, as a characteristic of the acute phase of schizophrenia, emerges after the first episode of psychosis. This suggests that visual context processing is a state-marker in schizophrenia and a biomarker of relapse and

Effects of short-term inpatient treatment on sensitivity to a size contrast illusion in first-episode psychosis and multiple-episode schizophrenia.

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Silverstein, Steven M; Keane, Brian P; Wang, Yushi; Mikkilineni, Deepthi; Paterno, Danielle; Papathomas, Thomas V; Feigenson, Keith

2013-01-01

In the Ebbinghaus illusion, a shape appears larger than its actual size when surrounded by small shapes and smaller than its actual size when surrounded by large shapes. Resistance to this visual illusion has been previously reported in schizophrenia, and linked to disorganized symptoms and poorer prognosis in cross-sectional studies. It is unclear, however, when in the course of illness this resistance first emerges or how it varies longitudinally with illness phase. We addressed these issues by having first-episode psychosis patients, multiple-episode schizophrenia patients and healthy controls complete a psychophysical task at two different time points, corresponding to hospital admission and discharge for patients. The task required judging the relative size of two circular targets centered on either side of the screen. Targets were presented without context (baseline), or were surrounded by shapes that made the size judgment harder or easier (misleading and helpful contexts, respectively). Context sensitivity was operationalized as the amount of improvement relative to baseline in the helpful condition minus the amount of decrement relative to baseline in the misleading condition. At hospital admission, context sensitivity was lower in the multiple-episode group than in the other groups, and was marginally less in the first episode than in the control group. In addition, schizophrenia patients were significantly more and less accurate than the other groups in the misleading and helpful conditions, respectively. At discharge, all groups exhibited similar context sensitivity. In general, poorer context sensitivity was related to higher levels of disorganized symptoms, and lower level of depression, excitement, and positive symptoms. Resistance to the Ebbinghaus illusion, as a characteristic of the acute phase of illness in schizophrenia, increases in magnitude after the first episode of psychosis. This suggests that visual context processing is a state-marker in

Superluminal velocities. Illusion or reality?

International Nuclear Information System (INIS)

Pereyra, P.; Simanjuntak, H.P.

2005-10-01

We study the time-evolution of electromagnetic wave packets through optical superlattices. We follow the time evolution (described by Maxwell equations) of Gaussian packets with centroid in different energy regions. The time spent by the wave packet inside an optical structure agrees extremely well with the superluminal experimental results and the phase time predictions. (author)

Rubber hand illusion affects joint angle perception.

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Martin V Butz

Full Text Available The Rubber Hand Illusion (RHI is a well-established experimental paradigm. It has been shown that the RHI can affect hand location estimates, arm and hand motion towards goals, the subjective visual appearance of the own hand, and the feeling of body ownership. Several studies also indicate that the peri-hand space is partially remapped around the rubber hand. Nonetheless, the question remains if and to what extent the RHI can affect the perception of other body parts. In this study we ask if the RHI can alter the perception of the elbow joint. Participants had to adjust an angular representation on a screen according to their proprioceptive perception of their own elbow joint angle. The results show that the RHI does indeed alter the elbow joint estimation, increasing the agreement with the position and orientation of the artificial hand. Thus, the results show that the brain does not only adjust the perception of the hand in body-relative space, but it also modifies the perception of other body parts. In conclusion, we propose that the brain continuously strives to maintain a consistent internal body image and that this image can be influenced by the available sensory information sources, which are mediated and mapped onto each other by means of a postural, kinematic body model.

The hologram as a space of illusion

Science.gov (United States)

Oliveira, Rosa M.

2013-03-01

One of the most interesting aspects of art holography is the study of 3D holographic image. Over the centuries, artists have chased the best way to represent the third dimension as similar to reality as possible. Several steps have been given in this direction, first using perspective, then photography, and later with movies, but all of these representations of reality wouldn't reach the complete objective. The realism of a 3D representation on a 2D support (paper, canvas, celluloid) is completely overcome by holography. In spite of the fact that the holographic plate or film is also a 2D support, the holographic image is a recording of all the information of the object contained in light. Our perception doesn't need to translate the object as real. It is real. Though immaterial, the holographic image is real because it exists in light. The same parallax, the same shape. The representation is no more an imitation of reality but a replacement of the real object or scene. The space where it exists is a space of illusion and multiple objects can occupy the same place in the hologram, depending on the viewer's time and place. This introduces the fourth dimension in the hologram: time, as well as the apparent conflict between the presence and the absence of images, which is just possible in holography.

Effects of visual illusion and transcutaneous electrical nerve stimulation on neuropathic pain in patients with spinal cord injury: A randomised controlled cross-over trial.

Science.gov (United States)

Özkul, Çağla; Kılınç, Muhammed; Yıldırım, Sibel Aksu; Topçuoğlu, Elif Yalçın; Akyüz, Müfit

2015-01-01

Chronic pain is a common consequence of spinal cord injury (SCI). No therapeutic drugs or drug groups are proven to be superior for neuropathic pain and treatments only aim to convert pain from dull to tolerable levels and not to remove it. This study was planned to compare the effect of visual illusion (VI) and transcutaneous electrical nerve stimulation (TENS) on pain intensity, pain quality and functional capacity in SCI patients with neuropathic pain. Twenty-four patients were included and randomly categorized into two groups. In the first group (n= 12), visual illusion was applied for first two weeks, 1 week wash out period and then TENS was applied for 2 weeks. In second group (n= 12), TENS was applied firstly, 1 week wash out and then %visual illusion VI were applied. Pain severity, pain quality, and functional capacity were assessed with the visual analog scale (VAS), the neuropathic pain scale (NPS), and the brief pain inventory (BPI), respectively. A pre-post-treatment and cross over design was used. Wilcoxon signed-rank tests were used for within group analyses. Mann-Whitney U tests were used for analyses that compared different groups. It was observed that pain intensity decrease immediately after both applications (VI: p= 0.07, TENS: p= 0.08). After TENS application for 2 weeks, it was observed that significant decrease in most (p= 0.04) and less (p= 0.02) pain intensity; while there was no significant decrease in pain intensity after 2 weeks for VI (p> 0.05). When findings of NPS were analyzed, hot (p= 0.047), sharp (p= 0.02), unpleasant (p= 0.03) and deep items (p= 0.047) decreased after VI application. When the results of BPI were detected, they were observed that the negative effect of pain on moving ability (p= 0.04) after visual illusion application and the negative effect of pain on mood (p= 0.03), relationships with others (p= 0.04) and sleep (p= 0.04) after TENS application decreased significantly. TENS and VI therapies can be successfully

Vestibular function in the space environment

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Von Baumgarten, R. J.; Harth, O.; Thuemler, R.; Baldrighi, G.; Shillinger, G. L., Jr.

1975-01-01

The present work presents new results about the interdependence of optical illusory sensations and eye movements in man. To establish to what degree certain illusions previously obtained during centrifugation and parabolic flight can be explained by eye movements and by neuronal integration in the brain, real eye movements were measured as they occurred in the dark without optical fixation, during rectilinear accelerations on the ground, and during weightlessness in parabolic flight. Results provide valuable insight into normal vestibular function as well as resolution of within-the-eye and behind-the-eye contributions to the above illusions.

The factory of illusions in the ‘Third Rome’:Circus Maximus as a space of fascist simulation

OpenAIRE

Kallis, Aristotle

2014-01-01

Although the site of the ancient Circus Maximus was one of the most loaded spaces of the Fascist ‘Third Rome’, it has received limited attention as a privileged site where a dizzying array of myths and illusions were entertained, simulated, and deposited as new Fascist layers on Rome’s urban and mnemonic palimpsest. Previously a decayed, ‘unsightly’, and overcrowded hodgepodge of layers of life, history, and memory, it was substantially restored, ruthlessly emptied of its previous life, and t...

Algeria: the illusions of oil wealth - CERI Studies No. 168

International Nuclear Information System (INIS)

Martinez, Luis

2010-09-01

Thirty years after the nationalisation of hydrocarbons Algeria's oil wealth seems to have disappeared judging by its absence in the country's indicators of well-being. In Algeria oil led to happiness for a few and sadness for many. The absence of controls over oil revenue led to the industries downfall. Since 2002 Algeria is again seeing oil wealth. The increase in the price per barrel from 30 to 147 dollars between 2002 and 2008 provided the country with unexpected revenue permitting it to accumulate funds estimated, in 2009, at 150 billion dollars. Abdelaziz Bouteflika, returned to a devastated Algeria to restore civil order, unexpectedly benefited from this price increase. Thus, in addition to national reconciliation he was able to offer Algeria renewed economic growth. However, given that the wounds of the 1990's are not entirely healed and the illusions of oil wealth have evaporated this unexpected return of financial abundance raises concerns. To what ends will this manna be put? Who will control it? Will it provoke new violence and conflict? (author)

Functional connectivity analysis of brain hemodynamics during rubber hand illusion.

Science.gov (United States)

Arizono, Naoki; Kondo, Toshiyuki

2015-08-01

Embodied cognition has been eagerly studied in the recent neuroscience research field. In particular, hand ownership has been investigated through the rubber hand illusion (RHI). Most of the research measured the brain activities during the RHI by using EEG, fMRI, etc., however, near-infrared spectroscopy (NIRS) has not yet been utilized. Here we attempt to measure the brain activities during the RHI task with NIRS, and analyze the functional connectivity so as to understand the relationship between NIRS features and the state of embodied cognition. For the purpose, we developed a visuo-tactile stimulator in the study. As a result, we found that the subjects felt illusory experience showed significant peaks of oxy-Hb in both prefrontal and premotor cortices during RHI. Furthermore, we confirmed a reliable causality connection from right prefrontal to right premotor cortex. This result suggests that the RHI is associated with the neural circuits underlying motor control. Therefore, we considered that the RHI with the functional connectivity analysis will become an appropriate model investigating a biomarker for neurorehabilitation, and the diagnosis of the mental disorders.

Experimental Induction of a Perceived “Telescoped” Limb Using a Full-Body Illusion

Science.gov (United States)

Schmalzl, Laura; Ehrsson, H. Henrik

2011-01-01

Phantom limbs refer to the sensation that an amputated or missing limb is still attached to the body. Phantom limbs may be perceived as continuous with the stump so as to resemble a normal limb, or as “telescoped” with the more distal portion of the phantom being perceived as having withdrawn within the stump. Telescoping tends to be related to increased levels of phantom pain, making it a clinically relevant phenomenon to investigate. In the current study we show that a full-body illusion can be used to induce the sensation of a telescoped limb in healthy individuals. For the induction of the full-body illusion, participants saw the body of a mannequin from a first person perspective while being subjected to synchronized visuo-tactile stimulation through stroking. Crucially, the mannequin was missing its left hand so as to resemble an amputee. By manipulating the positioning of the strokes applied to the mannequin's stump with respect to the participants’ hand we were able to evoke the sensation of the participants’ hand being located either below the stump or, more crucially, “inside” the stump, i.e., telescoped. In three separate experiments these effects were supported by complementary subjective data from questionnaires, verbally reported perceived location of the hand, and manual pointing movements indicating hand position (proprioceptive drift). Taken together our results show that healthy individuals can experience the body of an upper limb amputee as their own, and that this can be associated with telescoping sensations. This is a theoretically important observation as it shows that ownership of an entire body can be evoked in the context of gross anatomical incongruence for a single limb, and that telescoping sensations occur as a consequence of the body representation system trying to reduce this incongruence. Furthermore, the present study might provide a new platform for future studies of the relationship between telescoping and phantom

When men appear smaller or larger than they really are: preliminary evidence that women are fooled by size illusions in attractiveness judgment tasks

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Ludwig Yannick S.

2014-12-01

Full Text Available In humans, studies have shown that contrast illusions can affect perceptions of facial attractiveness and dominance. In non-human animals, recent research found that contrast illusions of size positively affected male mate value. In humans, male height is a potentially important indicator of mate value, with women preferring men taller than themselves. We tested in two studies whether height contrast illusions could affect women’s perceptions of male height and mate value, particularly attractiveness, dominance, and muscularity. Using computer-generated images of men of different heights standing in groups of three, 104 female participants rated targets either surrounded by shorter, same height, or taller distractors in a within-subject design. The second experiment (N=80 replicated and extended the first by making the images more realistic and adding natural backgrounds, suggesting that when participants are given a visual anchor, in order to get a better sense of the absolute height of the targets, the effects remain. In both studies, results showed that, compared with same height distractors, male targets were rated as taller when surrounded by shorter distractors, and as shorter when surrounded by taller distractors. Additionally, attractiveness, dominance, and muscularity perceptions were affected in a similar manner, with most of the differences in these appraisals being mediated by the perceived height differences. Therefore, differently sized distractors affected the perceived height and mate value of the targets, which were in effect all of the same constant size. These findings indicate that context dependent effects could potentially influence attractiveness judgments. The same man might thus be perceived as more attractive when surrounded by men of similar or smaller height, as opposed to when surrounded by men who are taller.

Fictitious Capital and the Elusive Quest in Understanding its Implications: Illusions and Paradoxes

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Joanilio Rodolpho Teixeira

2014-10-01

Full Text Available This paper deals with the interaction between fictitious capital and the neoliberal model of growth and distribution, inspired by the classical economic tradition. Our renewed interest in this literature has a close connection with the recent international crisis in the capitalist economy. However, this discussion takes as its point of departure the fact that standard economic theory teaches that financial capital, in this world of increasing globalization, leads to new investment opportunities which improve levels of growth, employment, income distribution, and equilibrium. Accordingly, it is said that such financial resources expand the welfare of people and countries worldwide. Here we examine some illusions and paradoxes of such a paradigm. We show some theoretical and empirical consequences of this vision, which are quite different and have harmful constraints.

What you see is what you feel : on the simulation of touch in graphical user interfaces

NARCIS (Netherlands)

Mensvoort, van K.M.

2009-01-01

This study introduces a novel method of simulating touch with merely visual means. Interactive animations are used to create an optical illusion that evokes haptic percepts like stickiness, stiffness and mass, within a standard graphical user interface. The technique, called optically simulated

Cooling the thermal grill illusion through self-touch.

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Kammers, Marjolein P M; de Vignemont, Frédérique; Haggard, Patrick

2010-10-26

Acute peripheral pain is reduced by multisensory interactions at the spinal level [1]. Central pain is reduced by reorganization of cortical body representations [2, 3]. We show here that acute pain can also be reduced by multisensory integration through self-touch, which provides proprioceptive, thermal, and tactile input forming a coherent body representation [4, 5]. We combined self-touch with the thermal grill illusion (TGI) [6]. In the traditional TGI, participants press their fingers on two warm objects surrounding one cool object. The warm surround unmasks pain pathways, which paradoxically causes the cool object to feel painfully hot. Here, we warmed the index and ring fingers of each hand while cooling the middle fingers. Immediately after, these three fingers of the right hand were touched against the same three fingers on the left hand. This self-touch caused a dramatic 64% reduction in perceived heat. We show that this paradoxical release from paradoxical heat cannot be explained by low-level touch-temperature interactions alone. To reduce pain, we often clutch a painful hand with the other hand. We show here that self-touch not only gates pain signals reaching the brain [7-9] but also, via multisensory integration, increases coherence of cognitive body representations to which pain afferents project [10]. Copyright © 2010 Elsevier Ltd. All rights reserved.

GABA concentration in superior temporal sulcus predicts gamma power and perception in the sound-induced flash illusion.

Science.gov (United States)

Balz, Johanna; Keil, Julian; Roa Romero, Yadira; Mekle, Ralf; Schubert, Florian; Aydin, Semiha; Ittermann, Bernd; Gallinat, Jürgen; Senkowski, Daniel

2016-01-15

In everyday life we are confronted with inputs of multisensory stimuli that need to be integrated across our senses. Individuals vary considerably in how they integrate multisensory information, yet the neurochemical foundations underlying this variability are not well understood. Neural oscillations, especially in the gamma band (>30Hz) play an important role in multisensory processing. Furthermore, gamma-aminobutyric acid (GABA) neurotransmission contributes to the generation of gamma band oscillations (GBO), which can be sustained by activation of metabotropic glutamate receptors. Hence, differences in the GABA and glutamate systems might contribute to individual differences in multisensory processing. In this combined magnetic resonance spectroscopy and electroencephalography study, we examined the relationships between GABA and glutamate concentrations in the superior temporal sulcus (STS), source localized GBO, and illusion rate in the sound-induced flash illusion (SIFI). In 39 human volunteers we found robust relationships between GABA concentration, GBO power, and the SIFI perception rate (r-values=0.44 to 0.53). The correlation between GBO power and SIFI perception rate was about twofold higher when the modulating influence of the GABA level was included in the analysis as compared to when it was excluded. No significant effects were obtained for glutamate concentration. Our study suggests that the GABA level shapes individual differences in audiovisual perception through its modulating influence on GBO. GABA neurotransmission could be a promising target for treatment interventions of multisensory processing deficits in clinical populations, such as schizophrenia or autism. Copyright © 2015 Elsevier Inc. All rights reserved.

The fascinating early history of optics! Archaeological optics 2009: our knowledge of the early history of lenses, mirrors, and artificial eyes!

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Enoch, Jay M.

2009-08-01

The early history of optics and vision science (older term: physiological optics) is indeed fascinating. The earliest known true lenses have been found in "eyes" of Egyptian statues which contain superb, complex, and well-polished eye-lens units. The oldest ones known are dated circa 2575 BCE = BC, Dynasty IV, Old Kingdom. These eye-lens units induce a fascinating and powerful visual illusion, but they are just too good to have been the first lenses, or even the first lenses of this design! So saying, no earlier dateable lenses have been found in Egypt or elsewhere. Recently, at the Boston Museum of Fine Arts, the writer noted a previously undetected lens in this series (a first in the Western Hemisphere). Oddly, dateable simpler magnifying lenses and burning glasses seem to have appeared later in time (?)! Manufactured mirrors are quite a bit older, dating from circa 6000 BCE in atal Hyk, located in south-central modern-day Turkey. Using these ancient mirrors, the image quality obtained is remarkable! Recently discovered ancient artificial eyes, located, in situ, in exhumed corpses, have been dated circa 3000 BCE (one discovered in Iran) 5000 BCE (one found in Spain). On the 3000 BCE artificial eye, there are drawn light rays (the writer believes these to be the oldest known depiction of light rays!) spreading out from (or passing into) the iris/ pupil border! Added interesting aspects associated with the early development of light-rays are considered. Thus, early optics can be readily traced back to the Neolithic era (the new stone age), and in some cases before that time period. We have deep roots indeed!

The Eyes Have It. Teaching Science.

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Leyden, Michael B.

1995-01-01

Features science concepts with accompanying activities teachers can use in the classroom. Presents a lesson in optics that utilizes optical illusions to illustrate scientific points and allows students to use the following processes: observing, communicating, controlling variables, hypothesizing, and gathering and interpreting data. (ET)

Enhancing transcranial direct current stimulation via motor imagery and kinesthetic illusion: crossing internal and external tools.

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Bodranghien, Florian; Manto, Mario; Lebon, Florent

2016-06-01

Transcranial direct current stimulation is a safe technique which is now part of the therapeutic armamentarium for the neuromodulation of motor functions and cognitive operations. It is currently considered that tDCS is an intervention that might promote functional recovery after a lesion in the central nervous system, thus reducing long-term disability and associated socio-economic burden. A recent study shows that kinesthetic illusion and motor imagery prolong the effects of tDCS on corticospinal excitability, overcoming one of the limitations of this intervention. Because changes in excitability anticipate changes in structural plasticity in the CNS, this interesting multi-modal approach might very soon find applications in neurorehabilitation.

The Logic of Reflection: Samuel Taylor Coleridge's "treatise on Logic"

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Land, Janet Sanders

Though others discuss Coleridge's interest in science, light imagery, the phenomenon of reflection, and his references to Newton and Opticks,^1 this is the first study to examine Coleridge's art in terms of optics, its developing theories, and the nature-of-light debate. This study examines Coleridge's early predilection for visions, illusions, and the supernatural and demonstrates that he gradually shifts from the supernatural to the scientific aspects of "visions" and "illusions," concentrating on causes of illusions and the effects of their deceptive qualities rather than their mystical features. By the 1820's, his preoccupation with illusions had become an interest in optics, fueled, no doubt, by the increasing controversy of the nature-of-light debate and the number of advances in optics resulting from the efforts of its opponents to prove their theories. Tracing the development of the debate, its escalation in the early nineteenth century, and the formation of Coleridge's opinion concerning key issues of the debate, I outline the evolution of Coleridge's theory of reflection and examine the exposition of that theory in his treatise, Logic (1981). Finally, I analyze the relationship between the advances in optics and Coleridge's concepts of thought and knowledge and his notion of the mind as an instrument of knowledge. These ideas in turn, altered his opinions concerning the validity of knowledge resulting from philosophic debate, scientific experiment, and poetic exploration. ftn^1John Beer, "Coleridge and Wordsworth on Reflection," The Wordsworth Circle 20 (1989): 20-29; Coleridge the Visionary. London: Chatto and Windus, 1959; and Coleridge's Poetic Intelligence. London: Macmillan, 1977 and M. H. Abrams Natural Supernaturalism: Tradition and Revolution in Romantic Literature. New York: Norton, 1971; and "Coleridge's 'A Light in Sound': Science, Metascience, and Poetic Imagination." The Correspondent Breeze: Essays on English Romanticism. Eds. M. H. Abrams

Metamaterial-enabled transformation optics

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Landy, Nathan

Transformation Optics is a design methodology that uses the form invariance of Maxwell's equations to distort electromagnetic fields. This distortion is imposed on a region of space by mimicking a curvilinear coordinate system with prescribed magnetoelectric material parameters. By simply specifying the correct coordinate transformation, researchers have created such exotic devices as invisibility cloaks, ``perfect'' lenses, and illusion devices. Unfortunately, these devices typically require correspondingly exotic material parameters that do not occur in Nature. Researchers have therefore turned to complex artificial media known as metamaterials to approximate the desired responses. However, the metamaterial design process is complex, and there are limitations on the responses that they achieve. In this dissertation, we explore both the applicability and limitations of metamaterials in Transformation Optics design. We begin in Chapter 2 by investigating the freedoms available to use in the transformation optics design process itself. We show that quasi-conformal mappings may be used to alleviate some of the complexity of material design in both two- and three-dimensional design. We then go on in Chapter 3 to apply this method to the design of a transformation-optics modified optic. We show that even a highly-approximate implementation of such a lens would retain many of the key performance feautures that we would expect from a full material prescription. However, the approximations made in the design of our lens may not be valid in other areas of transformation optical design. For instance, the high-frequency approximations of our lens design ignore the effects of impedance mismatch, and the approximation is not valid when the material parameters vary on the order of a wavelength. Therefore, in Chapter 4 we use other freedoms available to us to design a full-parameter cloak of invisibility. By tailoring the electromagnetic environment of our cloak, we are able to

The influence of embodiment on multisensory integration using the mirror box illusion.

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Medina, Jared; Khurana, Priya; Coslett, H Branch

2015-12-01

We examined the relationship between subcomponents of embodiment and multisensory integration using a mirror box illusion. The participants' left hand was positioned against the mirror, while their right hidden hand was positioned 12″, 6″, or 0″ from the mirror - creating a conflict between visual and proprioceptive estimates of limb position in some conditions. After synchronous tapping, asynchronous tapping, or no movement of both hands, participants gave position estimates for the hidden limb and filled out a brief embodiment questionnaire. We found a relationship between different subcomponents of embodiment and illusory displacement towards the visual estimate. Illusory visual displacement was positively correlated with feelings of deafference in the asynchronous and no movement conditions, whereas it was positive correlated with ratings of visual capture and limb ownership in the synchronous and no movement conditions. These results provide evidence for dissociable contributions of different aspects of embodiment to multisensory integration. Copyright © 2015 Elsevier Inc. All rights reserved.