WorldWideScience

Sample records for optical illusions

  1. Illusion optics

    Science.gov (United States)

    Lai, Yun; Ng, Jack; Chen, Huan-Yang; Zhang, Zhao-Qing; Chan, C. T.

    2010-09-01

    The technique of “transformation optics” establishes a correspondence between coordinate transformation and material constitutive parameters. Most of the transformation optics mappings give metamaterials that have graded positive refractive indices that can steer light in curves defined by the coordinate transformation. We will focus on those “folded-geometry mappings” that give negative refractive index materials that have special wave scattering properties. One interesting example is a kind of remote illusion device that can transform the stereoscopic image of an object into the illusion of some other object of our choice. The conceptual device can create the illusion without touching or encircling the object. For any incident wave, the device transforms the scattered waves of the original object into that of the object chosen for illusion outside a virtual boundary. We will illustrate some possible applications of this type of metamaterial remote device, including “cloaking at a distance,” partial cloaking, cloaking from an embedded device, revealing a hidden object inside a container, turning the image of one object into that of another object, and seeing through a wall. The feasibility of building this remote illusion device by metamaterials will also be discussed.

  2. Illusion induced overlapped optics.

    Science.gov (United States)

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

    2014-01-13

    The traditional transformation-based cloak seems like it can only hide objects by bending the incident electromagnetic waves around the hidden region. In this paper, we prove that invisible cloaks can be applied to realize the overlapped optics. No matter how many in-phase point sources are located in the hidden region, all of them can overlap each other (this can be considered as illusion effect), leading to the perfect optical interference effect. In addition, a singular parameter-independent cloak is also designed to obtain quasi-overlapped optics. Even more amazing of overlapped optics is that if N identical separated in-phase point sources covered with the illusion media, the total power outside the transformation region is N2I0 (not NI0) (I0 is the power of just one point source, and N is the number point sources), which seems violating the law of conservation of energy. A theoretical model based on interference effect is proposed to interpret the total power of these two kinds of overlapped optics effects. Our investigation may have wide applications in high power coherent laser beams, and multiple laser diodes, and so on.

  3. Design of optical switches by illusion optics

    Science.gov (United States)

    Shoorian, H. R.; Abrishamian, M. S.

    2013-05-01

    In this paper, illusion optics theory is employed to form Bragg gratings in an optical waveguide in order to design an optical switch. By using an illusion device at a certain distance from the waveguide, the effective refractive index of the waveguide is remotely modulated, turning the waveguide into a distributed Bragg reflector (DBR) which blocks the waves at a stop band. By removing the illusion device, the waves propagate through the waveguide again. In addition, this method is used to remotely tune DBR optical properties such as resonant frequency and bandwidth in a wide range, which leads to a tunable filter for optical switching applications. Finally, using an illusion device at a distance, an optical cavity is created by inserting defects remotely in a DBR without any physical damage in the primary device.

  4. Fiber Optics: No Illusion.

    Science.gov (United States)

    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)

  5. Optical Illusions and Effects on Clothing Design

    Directory of Open Access Journals (Sweden)

    Saliha AĞAÇ

    2015-06-01

    Full Text Available “Visual perception” is in the first ranking between the types of perception. Gestalt Theory of the major psychological theories are used in how visual perception realizes and making sense of what is effective in this process. In perception stage brain tak es into account not only stimulus from eyes but also expectations arising from previous experience and interpreted the stimulus which are not exist in the real world as if they were there. Misperception interpretations that brain revealed are called as “Pe rception Illusion” or “Optical Illusion” in psychology. Optical illusion formats come into existence due to factors such as brightness, contrast, motion, geometry and perspective, interpretation of three - dimensional images, cognitive status and color. Opti cal illusions have impacts of different disciplines within the study area on people. Among the most important types of known optical illusion are Oppel - Kundt, Curvature - Hering, Helzholtz Sqaure, Hermann Grid, Muller - Lyler, Ebbinghaus and Ponzo illusion etc . In fact, all the optical illusions are known to be used in numerous area with various techniques and different product groups like architecture, fine arts, textiles and fashion design from of old. In recent years, optical illusion types are frequently us ed especially within the field of fashion design in the clothing model, in style, silhouette and fabrics. The aim of this study is to examine the clothing design applications where optical illusion is used and works done in this subject. Some research of the design with the changing fashion of clothes of different types of optical illusions is discussed with examples of their effects on visual perception. In the study, optical illusory clothing models are scanned by visual analysis from documents like film , video, picture, web pages. The findings were analyzed in terms of the surface and design and effects of the optical illusion on clothing design has tried to put

  6. Illusion optics in chaotic light

    Science.gov (United States)

    Zhang, Su-Heng; Gan, Shu; Xiong, Jun; Zhang, Xiangdong; Wang, Kaige

    2010-08-01

    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.

  7. 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…

  8. Geometric-optical illusions at isoluminance.

    Science.gov (United States)

    Hamburger, Kai; Hansen, Thorsten; Gegenfurtner, Karl R

    2007-12-01

    The idea of a largely segregated processing of color and form was initially supported by observations that geometric-optical illusions vanish under isoluminance. However, this finding is inconsistent with some psychophysical studies and also with physiological evidence showing that color and luminance are processed together by largely overlapping sets of neurons in the LGN, in V1, and in extrastriate areas. Here we examined the strength of nine geometric-optical illusions under isoluminance (Delboeuf, Ebbinghaus, Hering, Judd, Müller-Lyer, Poggendorff, Ponzo, Vertical, Zöllner). Subjects interactively manipulated computer-generated line drawings to counteract the illusory effect. In all cases, illusions presented under isoluminance (both for colors drawn from the cardinal L-M or S-(L+M) directions of DKL color space) were as effective as the luminance versions (both for high and low contrast). The magnitudes of the illusion effects were highly correlated across subjects for the different conditions. In two additional experiments we determined that the strong illusions observed under isoluminance were not due to individual deviations from the photometric point of isoluminance or due to chromatic aberrations. Our findings show that our conscious percept is affected similarly for both isoluminance and luminance conditions, suggesting that the joint processing for chromatic and luminance defined contours may extend well beyond early visual areas.

  9. Unique Optical Illusions From A Magician's Perspective

    Science.gov (United States)

    Rosenthal, Ken

    1983-10-01

    The stage and close-up magicians have employed various types of optical effects in the presentation of magic illusions. Although certain magical effects "are done with mirrors", many other feats of magic employ no mirrors at all, but other optical-type devices in certain instances. The magician has relied on his magical creativity, misdirection, and showmanship, often more than certain optical and engineering-type devices for achievement of the magical effect. However, certain technical devices have always been a part of the magician's "bag-of-tricks". A brief overview of the magic, patent, and engineering literature is presented detailing what optical devices and effects magicians have and will continue to use. An important criterion is that the optical effect, however simple or complex, when combined with the intended illusion, give the audience the experience of an entertaining, mysterious, magical effect--not a science class type demonstration. Several examples are presented of optical effects in magic tricks which have been successfully employed. The main purpose of this paper is not to expose the secrets of magic, but to allow the optical engineer to gain an appreciation and understanding of how the magician develops and performs new effects, so that new optical devices and techniques might find their place in a show of illusions.

  10. Anomalous Mirror Symmetry Generated by Optical Illusion

    Directory of Open Access Journals (Sweden)

    Kokichi Sugihara

    2016-04-01

    Full Text Available This paper introduces a new concept of mirror symmetry, called “anomalous mirror symmetry”, which is physically impossible but can be perceived by human vision systems because of optical illusion. This symmetry is characterized geometrically and a method for creating cylindrical surfaces that create this symmetry is constructed. Examples of solid objects constructed by a 3D printer are also shown.

  11. Cloaks and antiobject-independent illusion optics based on illusion media

    Science.gov (United States)

    Li, Zhou; Zang, XiaoFei; Cai, Bin; Shi, Cheng; Zhu, YiMing

    2013-11-01

    Based on the transformation optics, we propose a new strategy of illusion media consisting of homogeneous and anisotropic materials. By utilizing the illusion media, invisible cloak is theoretically realized, in which objects covered with the illusion media could not be detected. The cloak here allows neither the propagation of light around the concealed region nor compensates the scattering field of object outside the media. What the cloak does is to shift the region into another place where outside the trace of light, so that objects in that region can disappear. Another application of the illusion media is to create the antiobject-independent illusion optics which means that two objects appear to be like some other objects of our choice. Finite element simulations for two-dimensional cases have been performed to prove these ideas.

  12. Remote nano-optical beam focusing lens by illusion optics

    Science.gov (United States)

    Margousi, David; Shoorian, Hamed Reza

    2014-08-01

    In this paper, as a new application of illusion optics, a nano-optical plasmonic focusing lens structure is proposed to manipulate the light remotely by employing illusion optics theory. Plasmonic nano-optic lenses that enable super-focusing beyond the diffraction limit have been proposed as an alternative to the conventional dielectric-based refractive lenses. In the presence of an illusion device, the electromagnetic plane-waves can penetrate into a metal layer and a clear focus appears. When the illusion device is removed, waves are blocked to transmit through the metal wall. In comparison with conventional methods, our proposed method avoids any physical changes or damages in the original structure. The proposed structure can be realized by isotropic layered materials, using effective medium theory. The special feature of the proposed structure and the device concepts introduced in this work gives it an opportunity to be used as a flexible element in ultrahigh nano-scale integrated circuits for miniaturization and tuning purposes.

  13. Optical Illusions: A Presentation for High School Mathematics Students.

    Science.gov (United States)

    Brandes, Louis Grant

    1983-01-01

    Optical illusions are assumed to be of interest to high school mathematics students. The article indicates how a topic can be both educational and entertaining. Readers are invited to try to construct some illusions on their own, and to see if they can classify them. (MP)

  14. Overlapping illusions by transformation optics without any negative refraction material

    Science.gov (United States)

    Sun, Fei; He, Sailing

    2016-01-01

    A novel method to achieve an overlapping illusion without any negative refraction index material is introduced with the help of the optic-null medium (ONM) designed by an extremely stretching spatial transformation. Unlike the previous methods to achieve such an optical illusion by transformation optics (TO), our method can achieve a power combination and reshape the radiation pattern at the same time. Unlike the overlapping illusion with some negative refraction index material, our method is not sensitive to the loss of the materials. Other advantages over existing methods are discussed. Numerical simulations are given to verify the performance of the proposed devices.

  15. Magic, illusions, and bloopers and blunders in optics

    Science.gov (United States)

    Fischer, Robert E.

    2001-12-01

    This paper presents the use of optics as it relates to the various forms of illusions and magic, and we will present many of the best optical illusions to demonstrate the use of optics. In magic and visual illusions, objects are made to appear different from how we expect them to appear. Performing such illusions show us things that are impossible based on our preconceived knowledge base. This includes levitation, sawing a lady in half, or creating other similar effects. Optical illusions often take the form of illusions of relative size, shifting perception of items, and other ways of fooling the eye, the mind and the brain. These effects are all highly deceiving to the viewer. In addition to optical illusions, there is close up, parlor and stage magic. These would include classical effects as well as contemporary effects with items such as cards, coins, rings, etc. Here too the goal of the magician is to totally mystify the audience. Another topic of the paper is

  16. Paradoxical form of filled/empty optical illusion.

    Science.gov (United States)

    Wackermann, Jiri; Kastner, Kristina

    2009-01-01

    The filled/empty illusion (Oppel-Kundt) is one of the oldest geometrical-optical illusions, but the determinants of the illusion are not yet sufficiently understood. We studied magnitude of the illusory effect as a function of the height of vertical strokes subdividing a spatial extension of fixed length, using the psychophysical standard-variable matching paradigm. For vertical strokes shorter than, or of the same height as strokes delimiting the standard, the length was over-reproduced consistently with earlier studies of the illusion. However, for vertical strokes three times longer than the delimiters, the illusory effect paradoxically decreased, and attained negative values in two of six subjects. The magnitude of the effect thus depends on the patterning of the space between the delimiters, not merely on the number of subdividing elements.

  17. Experimental realization of a broadband illusion optics device

    CERN Document Server

    Li, Chao; Liu, Xiao; Li, Fang; Fang, Guangyou; Chen, Huanyang; Chan, C T

    2010-01-01

    We experimentally demonstrate the first metamaterial "illusion optics" device - an "invisible gateway" by using a transmission-line medium. The device contains an open channel that can block electromagnetic waves at a particular frequency range. We also demonstrate that such a device can work in a broad frequency range.

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

    Science.gov (United States)

    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.

  19. Overlapped illusion optics: a perfect lens brings a brighter feature

    Science.gov (United States)

    Xu, Yadong; Du, Shengwang; Gao, Lei; Chen, Huanyang

    2011-02-01

    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.

  20. Overlapped illusion optics: a perfect lens brings a brighter feature

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Illusions in the spatial sense of the eye: geometrical-optical illusions and the neural representation of space.

    Science.gov (United States)

    Westheimer, Gerald

    2008-09-01

    Differences between the geometrical properties of simple configurations and their visual percept are called geometrical-optical illusions. They can be differentiated from illusions in the brightness or color domains, from ambiguous figures and impossible objects, from trompe l'oeil and perspective drawing with perfectly valid views, and from illusory contours. They were discovered independently by several scientists in a short time span in the 1850's. The clear distinction between object and visual space that they imply allows the question to be raised whether the transformation between the two spaces can be productively investigated in terms of differential geometry and metrical properties. Perceptual insight and psychophysical research prepares the ground for investigation of the neural representation of space but, because visual attributes are processed separately in parallel, one looks in vain for a neural map that is isomorphic with object space or even with individual forms it contains. Geometrical-optical illusions help reveal parsing rules for sensory signals by showing how conflicts are resolved when there is mismatch in the output of the processing modules for various primitives as a perceptual pattern's unitary structure is assembled. They point to a hierarchical ordering of spatial primitives: cardinal directions and explicit contours predominate over oblique orientation and implicit contours (Poggendorff illusion); rectilinearity yields to continuity (Hering illusion), point position and line length to contour orientation (Ponzo). Hence the geometrical-optical illusions show promise as analytical tools in unraveling neural processing in vision.

  2. Design of optical cloaks and illusion devices along a circumferential direction in curvilinear coordinates

    Science.gov (United States)

    Chen, Tungyang; Yu, Shang-Ru

    2010-11-01

    We propose a cloaking and illusion device of circumferential topology based on the concept of transformation optics. The device is capable to cloak an object and/or simultaneously generate illusion images along a circumferential direction in curvilinear orthogonal coordinates. This feature allows us to construct multiple illusions in different ways, irrespective of the profile and direction of incident wave. Particularly when the device is served as a building brick of a larger device, one can generate a circumferential array of illusions in a periodic or any preferred pattern. We demonstrate the effectiveness of the proposed illusion devices by carrying out full wave simulations based on finite element calculations.

  3. Simulating Visual Learning and Optical Illusions via a Network-Based Genetic Algorithm

    Science.gov (United States)

    Siu, Theodore; Vivar, Miguel; Shinbrot, Troy

    We present a neural network model that uses a genetic algorithm to identify spatial patterns. We show that the model both learns and reproduces common visual patterns and optical illusions. Surprisingly, we find that the illusions generated are a direct consequence of the network architecture used. We discuss the implications of our results and the insights that we gain on how humans fall for optical illusions

  4. A study on some optical illusions based upon the theory of inducing field.

    Science.gov (United States)

    Ge, Sheng; Saito, Takashi; Wu, Jing-Long; Iramina, K

    2006-01-01

    The study of optical illusion is an important method to elucidate the mechanism of visual perception. However, many details about the cause of optical illusions are still unclear. In this research, based on the characteristic of the physiological structure of the retina, we proposed an on-center receptive field model of the retina. Using this model, we simulated the distributions of the inducing field of some visual stimulus. Comparing to the past studies' results, the validity of the proposed model was proofed. Furthermore, we simulated the distributions of the inducing field of some typical illusions. The simulation results can explain these illusion phenomenon rationally. Therefore, it suggested that some of illusions are probably engendered by the distributions of the inducing field in the retina which generated by the illusions stimuli. The practicality of the proposed model was also verified.

  5. Cosmic Acceleration as an Optical Illusion

    CERN Document Server

    Skarke, Harald

    2015-01-01

    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 mainly due to effects beyond second order in perturbation theory.

  6. Cosmic acceleration as an optical illusion

    Energy Technology Data Exchange (ETDEWEB)

    Skarke, Harald [Technische Universitaet Wien, Institut fuer Theoretische Physik, Vienna (Austria)

    2017-03-15

    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.)

  7. 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'…

  8. Optical illusions and augmented graphics in guidance and control

    Science.gov (United States)

    Kelley, Robert S.; Tuggle, Francis D.

    1993-03-01

    Piloting and many related control activities, especially remote manipulation via teleoperations and robotics, stand to benefit substantially from better means of communication between controller and controlled. We have investigated one such approach: the use of augmented displays on a cathode ray terminal (CRT) for controlling simulation motion is microgravity. Such displays, which have been shown to be highly effective in a variety of applications, provide information to the operator which goes beyond that which is found in nature, and thereby emphasize important aspects of a task and minimize irrelevant ones. Using this approach, we attempted to develop stylized graphical displays, incorporating augmented feedback by distorting the background of the scene under display, for purposes of flight control and/or control of a robotic arm. Besides attempting to utilize transformations of the scene itself for informational purposes, the displays we developed represent significant departures from previous methods in two notable respects. First, we have attempted to design our instrumentation to make use of peripheral rather than exclusively foveal vision, thus broadening the bandwidth of perception by vision. Second, we attempted to incorporate optical illusions intended to enhance the perception of depth and apparent motion to provide better and more compelling feedback for the operator performing the task.

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

    Science.gov (United States)

    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.

  10. [Influence of "optical illusion" on detectability in diagnosis for head CT images: participation of optical illusion of light perception in medical image reading and diagnosis].

    Science.gov (United States)

    Henmi, Shuichi

    2006-07-20

    Even if the visual impression of the photographic density of the brain in head CT images is shown as physically the same, it is known that optical illusions of lightness perception (assimilation, contrast, picture frame effect, etc.) occur and that practical density can be observed psychologically differently, according to differences in the color of the skull and background, and differences in cases (differences in picture pattern). Therefore, in this study, in order to clarify the influence of optical illusion on detectability in diagnosis, the author attempted to compare detectability in four sample cases, consisting of acute cerebral infarction (1), acute epidural hematoma (1), and chronic subdural hematoma (2), using visual subjective evaluation. In the case of acute cerebral infarction, there was no significant difference in detectability between the original image and the virtual images. Further, it clarified that the original head CT image (acute epidural hematoma) with the high-density hematoma recognized at the marginal limited part of the brain was inferior to virtual images in detectability, while it clarified that the original head CT image (chronic subdural hematoma) with the low-density hematoma was superior to virtual images in detectability, because of visual psychological emphasis on the difference of the film contrast between the hematoma and white skull.

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

    Science.gov (United States)

    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.

  12. Radar illusion via metamaterials

    Science.gov (United States)

    Jiang, Wei Xiang; Cui, Tie Jun

    2011-02-01

    An optical illusion is an image of a real target perceived by the eye that is deceptive or misleading due to a physiological illusion or a specific visual trick. The recently developed metamaterials provide efficient approaches to generate a perfect optical illusion. However, all existing research on metamaterial illusions has been limited to theory and numerical simulations. Here, we propose the concept of a radar illusion, which can make the electromagnetic (EM) image of a target gathered by radar look like a different target, and we realize a radar illusion device experimentally to change the radar image of a metallic target into a dielectric target with predesigned size and material parameters. It is well known that the radar signatures of metallic and dielectric objects are significantly different. However, when a metallic target is enclosed by the proposed illusion device, its EM scattering characteristics will be identical to that of a predesigned dielectric object under the illumination of radar waves. Such an illusion device will confuse the radar, and hence the real EM properties of the metallic target cannot be perceived. We designed and fabricated the radar illusion device using artificial metamaterials in the microwave frequency, and good illusion performances are observed in the experimental results.

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

    Science.gov (United States)

    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.

  14. Commentary on the Radius of the Sun: Optical Illusion or Manifestation of a Real Surface?

    Directory of Open Access Journals (Sweden)

    Robitaille P.-M.

    2013-04-01

    Full Text Available In modern solar theory, the photospheric surface merely act s as an optical illusion. Gases cannot support the existence of such a boundary. Conve rsely, the liquid metallic hydrogen model supports the idea that the Sun has a distinct s urface. Observational as- tronomy continues to report increasingly precise measures of solar radius and diameter. Even the smallest temporal variations in these parameters w ould have profound impli- cations relative to modeling the Sun and understanding clim ate fluctuations on Earth. A review of the literature convincingly demonstrates that th e solar body does indeed pos- sess a measurable radius which provides, along with previou s discussions (Robitaille P.M. On the Presence of a Distinct Solar Surface: A Reply to He rv ́e Faye. Progr. Phys. , 2011, v. 3, 75–78., the twenty-first line of evidence that t he Sun is comprised of condensed-matter.

  15. The Application of the Optical Illusion Principle in Clothing Design%视错觉原理在女装款式设计中的应用

    Institute of Scientific and Technical Information of China (English)

    许平山; 宿伟

    2015-01-01

    The principle of optical illusion is applied in designing the clothing to perfect the body defects, which plays an important role in the design of special individuals. This paper, based on the principle of optical illusion and the specific examples of dress design, mainly researches the application relationship between the principle of optical illusion and clothing design. Besides, it discusses the influence of shape illusion, the division illusion, the comparison illusion on the styles of human body dressing in order to explore the feasible way to connecting the principle of optical illusion with the real situation of dressing.%利用视错觉原理设计的服装能有效修正人体的体型缺陷,对个性化人群的服装设计起到了十分重要的作用. 以视错觉原理为依据,以款式设计实例为手段,探索视错觉原理与款式设计之间的应用关系,重点探讨了形状视错、分割视错、对比视错对人体着装款式设计的影响,提出把视错觉理论与着装实际相结合的可行性的策略.

  16. 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.

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

    Science.gov (United States)

    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.

  18. 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.

  19. Exterior optical cloaking and illusions by using active sources: A boundary element perspective

    Science.gov (United States)

    Zheng, H. H.; Xiao, J. J.; Lai, Y.; Chan, C. T.

    2010-05-01

    Recently, it was demonstrated that active sources can be used to cloak any objects that lie outside the cloaking devices [F. Guevara Vasquez, G. W. Milton, and D. Onofrei, Phys. Rev. Lett. 103, 073901 (2009)]. Here, we propose that active sources can create illusion effects so that an object outside the cloaking device can be made to look like another object. Invisibility is a special case in which the concealed object is transformed to a volume of air. From a boundary element perspective, we show that active sources can create a nearly “silent” domain which can conceal any objects inside and at the same time make the whole system look like an illusion of our choice outside a virtual boundary. The boundary element method gives the fields and field gradients, which can be related to monopoles and dipoles, on continuous curves which define the boundary of the active devices. Both the cloaking and illusion effects are confirmed by numerical simulations.

  20. 形态错视在鞋类造型设计中的应用%The Optical Illusion of Shapes Apple in Shoes Modelling Design

    Institute of Scientific and Technical Information of China (English)

    彭飘林

    2013-01-01

    Analyzed on the basic of the basic kinds and characteristics of optical illusion of shapes,Com-bined with points of shoes-molding design,summarized application rules of optical illusion of shapes in shoes-molding design.%在分析形态错视的基本类型及特征的基础上,结合鞋类造型设计的要求,总结了形态错视在鞋类造型设计中的应用规律。

  1. Experimental Realization of a Circuit-Based Broadband Illusion-Optics Analogue

    Science.gov (United States)

    Li, Chao; Meng, Xiankun; Liu, Xiao; Li, Fang; Fang, Guangyou; Chen, Huanyang; Chan, C. T.

    2010-12-01

    We experimentally demonstrate the first metamaterial “illusion optics” device—an “invisible gateway” by using a transmission-line medium. The device contains an open channel that can block waves at a particular frequency range. We also demonstrate that such a device can work in a broad frequency range.

  2. [Influence of "optical illusion" on the detectability of pneumothorax in diagnosis for chest CT images: substantiation by visual psychological simulation images].

    Science.gov (United States)

    Henmi, Shuichi

    2008-10-20

    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.

  3. Determinants of filled/empty optical illusion: Influence of luminance contrast and polarity.

    Science.gov (United States)

    Wackermann, Jiří

    2012-01-01

    Subjective estimates of lengths or areas in the visual field depend on the visual contents of the estimated space (filled/empty or Oppel-Kundt illusion). We studied the dependence of this phenomenon on the presentation mode (white on black vs. black on white background), and on the figure/ground contrast. We found, as expected, overestimation of the filled part of the figure for both contrast polarities. The expansion effect was found to be an increasing function of the absolute luminance contrast, and was consistently higher for the negative (luminant figures on a dark background) than for the positive polarity. The contrast factor contributes from one-fifth to one-third of the total effect. Possible interpretations in terms of known sensory phenomena (irradiation, lateral interactions) or higher, integrative functions are discussed.

  4. Application of Intelligent Design of Optical Illusions in Fashion Design%智能化视幻图案在服装设计中的应用

    Institute of Scientific and Technical Information of China (English)

    张琼

    2016-01-01

    基于互联网多媒体服装设计技术,智能化视幻图案可使服饰作品带给人全新视觉感受,它可以调整人体比例,美化身形,增加服饰的趣味性,提供丰富的视觉效果.文中针对服装设计中智能化视幻图案的发展及特点进行讨论,为智能化视幻图案的应用提供参考.%Based on the Internet multimedia fashion design technology,intelligent optical illusions design can bring a brand-new visual experience to dress.It can adjust body proportion,beautify body,make dress more interesting,provide a rich visual effect.In this paper,the development of the intelligent design of optical illusions in clothing design and characteristics were studied,which provide theoretical basis for the application of intelligent design of optical illusions.

  5. Application of Optical Illusion in Graphic Design%浅析视错觉手段在平面设计中的运用技巧

    Institute of Scientific and Technical Information of China (English)

    梁烨

    2011-01-01

    现代设计已经步入了一个崭新的时代,视错觉技法以其智慧性、趣味性和简洁性而越来越受到设计者的青睐,它在平面设计中的应用对于增强作品的内涵、加深观者的印象有着重要作用.本文对视错视图形表现手法进行了基本分类,初步分析了视错觉的类型及其在设计领域的应用.%The modern design has entered into a new era.Techniques of optical illusion with wisdom, interest and simplicity more and more get the favour of designers, and plays an important role in enhancing the connotation of the works, deepening the viewer's impression in graphic design.This paper conducted the basic classification to graphic expression skills of optical illusion, and analyzed the types of optical illusion and its applications in design areas.

  6. Determinants of filled/empty optical illusion: Search for the locus of maximal effect.

    Science.gov (United States)

    Wackermann, Jiri; Kastner, Kristina

    2010-01-01

    A subdivided path in the visual field usually appears longer than an empty path of the same length. This phenomenon, known as the filled/empty or Oppel-Kundt illusion, depends on multiple properties of the visual stimulus, but the functional dependences have not been yet precisely characterized. We studied the illusory effect as a function of its two main determinants, the height of vertical strokes subdividing a spatial interval of a fixed length (visual angle 2.8 degree) and the number of the filling strokes, using the standard-variable distance matching paradigm. Non-monotonic dependence of the effect (over-reproduction of the spatial extension) on the varied parameters was observed in two experimental series. In the first series, the maximum effect was obtained for the fillers height roughly equal to the delimiters height (visual angle 0.25 degree); in the second series, the maximum effect was obtained for 11-13 equispaced fillers, and more accurately estimated to 15-16 as a result of a functional fit. Both data series were successfully modeled by curves generated by a single two-parametric system of form functions. Problems of determination of the maximum effect are discussed, and arguments for a genuinely multivariate approach are presented.

  7. Robotically enhanced rubber hand illusion.

    Science.gov (United States)

    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.

  8. 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)

  9. Determinants of filled/empty optical illusion: differential effects of patterning.

    Science.gov (United States)

    Wackermann, Jiri

    2012-01-01

    A subdivided path in the visual field appears longer than an empty path of the same length. This effect may be attributed to the division of the path into multiple segments, or to an influence of the visual elements used to mark the subdivision, and thus filling-up the estimated space. To address this question, we used two series of stimuli, in which the spatial distribution of the filling optical mater, or the form of the dividers, was varied while the relative coverage of the filled space was kept constant. We found significant dependence of the effect magnitude on a number of filling elements as well as on their form. These results indicate that the illusory space expansion is not merely an effect of 'filling-up' the space, but it also depends on the filling pattern. Consequences of these findings for the theory of the Oppel-Kundt phenomenon are briefly discussed.

  10. The Application of Optical Illusion in Space Design%视错觉在空间设计中的运用

    Institute of Scientific and Technical Information of China (English)

    刘婧

    2014-01-01

    视错觉主要是人以及动物在观察物体时选择参照物不当或是本能的心理上因素而产生的视觉偏差。本文分析了错觉的产生的原因,按不同的现象和成因,把视错觉巧妙运用到空间设计之中,使之更加的和谐,增加其趣味性。%The optical ilusion is the visual deviation that people and animals select the improper reference or the instinct psychological factors in the observation object. This article analyzes the cause of the illusion. And according to different phenomena and causes, the author put the optical ilusion cle-ver applied in space design, makes it more harmonious and in-creases their interest.

  11. 服饰中的色彩视错觉分析%Analysis of Color Optical Illusion of Clothing

    Institute of Scientific and Technical Information of China (English)

    涂毅佳; 李晓蓉

    2012-01-01

    ;The quantitative analysis table of color vision illusion was created based on the application of color vision illusion in clothing as a core and dress elements as a starting point. Every factor in the quantitative analysis table was explored from the view of color psychology in order to analyze the of clothing.%以色彩视错觉在服装中的应用为核心,以着装要素为出发点,建立一种色彩视觉差的定量分析表,并从色彩心理学的角度阐述各影响因素,为服装的感觉、知觉进行科学的分析。

  12. Sex differences in susceptibility to the Poggendorff illusion.

    Science.gov (United States)

    Declerck, Carolyn; De, Brabander Bert

    2002-02-01

    This study presents experimental results indicating that there are sex differences in the susceptibility to a geometric optical illusion. Participants (57 male and 39 female undergraduate students) performed 3 trials on a test involving the Poggendorff illusion. Analysis indicated that the magnitude of the illusion diminished significantly with each trial and that the percent perceived error was significantly larger for women than for men. This finding is consistent with the numerous studies which have indicated better visuospatial abilities for men than for women.

  13. 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.

  14. The Ehrenstein illusion

    OpenAIRE

    Dresp-Langley, Birgitta

    2009-01-01

    International audience; The original Ehrenstein illusion was first described by Walter Ehrenstein senior (Ehrenstein, 1941, 1954). It is generated by a configuration of four line segments which induce the perception of a so-called illusory figure at the centre of the configuration (Fig 1a). This illusion is part of a class of visual perceptual phenomena referred to as contrast or brightness illusions, as explained in detail in this state-of-the-art review.

  15. PERFECT DEMAND ILLUSION

    Directory of Open Access Journals (Sweden)

    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».

  16. [A review of face illusions].

    Science.gov (United States)

    Kitaoka, Akiyoshi

    2012-07-01

    A variety of "face illusions," including the gaze illusion, face inversion effects, geometrical illusions, reversible figures, and other interesting phenomena related to face perception, are reviewed in the present report, with many sample images. The "gaze illusion" or the illusion of eye direction includes the Wollaston illusion, the luminance-induced gaze shift, the Bogart illusion, the eye-shadow-dependent gaze illusion, the Mona Lisa effect, etc. "Face inversion effects" refer to the Thatcher illusion, the fat face-thin illusion, underestimation of the upright face, the nose-shortening illusion of the inverted face, etc. "Geometrical illusions" include the Lee-Freire illusion, Yang's iris illusion, overestimation of the farther eye, the eye-shadow-dependent eye-size illusion, etc. "Reversible figures" contain the whole-part reversible figure, Rubin's vase-face illusion, or hybrid images. "Other interesting phenomena" include the flashed face distortion effect, the presidential illusion, predominance of the mouth or eyebrows over eye expression, the eye direction aftereffect, etc. It is suggested that some of these phenomena are highly specific to face perception.

  17. 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.

  18. Illusions and Cloaks for Surface Waves

    Science.gov (United States)

    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.

  19. Perception, illusions and Bayesian inference.

    Science.gov (United States)

    Nour, Matthew M; Nour, Joseph M

    2015-01-01

    Descriptive psychopathology makes a distinction between veridical perception and illusory perception. In both cases a perception is tied to a sensory stimulus, but in illusions the perception is of a false object. This article re-examines this distinction in light of new work in theoretical and computational neurobiology, which views all perception as a form of Bayesian statistical inference that combines sensory signals with prior expectations. Bayesian perceptual inference can solve the 'inverse optics' problem of veridical perception and provides a biologically plausible account of a number of illusory phenomena, suggesting that veridical and illusory perceptions are generated by precisely the same inferential mechanisms.

  20. The Methadone Illusion

    Science.gov (United States)

    Lennard, Henry L.; And Others

    1972-01-01

    Methadone treatment for heroin addiction does not touch the roots of the drug problem" and to think that the use of another drug can solve the profound and complex task facing us is indeed an illusion." (Author/AL)

  1. [The Hermann grid illusion: the classic textbook interpretation is obsolete].

    Science.gov (United States)

    Bach, M

    2009-10-01

    The Hermann grid is an optical illusion in which the crossings of white grid lines appear darker than the grid lines outside the crossings. The illusion disappears when one fixates the crossings. The discoverer, Ludimar Hermann (1838-1914), interpreted the illusion as evidence for lateral connections in the retina. In most textbooks on sensory physiology and ophthalmology, the Hermann grid illusion serves to illustrate "lateral inhibition." This paper summarises new findings that show that the classic explanation is incomplete. In 2004, a seemingly subtle modification, a small undulation of the grid lines, was shown to demolish the illusion. In 2007, a more convincing explanation appeared: An artificial neural network was trained for "lightness constancy"- the ability of our visual system to interpret luminance in the interest of object recognition, independent of illumination. After having learned lightness constancy, the network was subjected to a number of lightness illusions, among them the Hermann grid illusion. An analysis of the coupling constants of this neural network promises to further our understanding of the Hermann grid illusion.

  2. 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.

  3. 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

  4. 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.

  5. The Poggendorff illusion driven by real and illusory contour: Behavioral and neural mechanisms.

    Science.gov (United States)

    Shen, Lu; Zhang, Ming; Chen, Qi

    2016-05-01

    The Poggendorff illusion refers to the phenomenon that the human brain misperceives a diagonal line as being apparently misaligned once the diagonal line is interrupted by two parallel edges, and the size of illusion is negatively correlated with the angle of interception of the oblique, i.e. the sharper the oblique angle, the larger the illusion. This optical illusion can be produced by both real and illusory contour. In this fMRI study, by parametrically varying the oblique angle, we investigated the shared and specific neural mechanisms underlying the Poggendorff illusion induced by real and illusory contour. At the behavioral level, not only the real but also the illusory contours were capable of inducing significant Poggendorff illusion. The size of illusion induced by the real contour, however, was larger than that induced by the illusory contour. At the neural level, real and illusory contours commonly activated more dorsal visual areas, and the real contours specifically activated more ventral visual areas. More importantly, examinations on the parametric modulation effects of the size of illusion revealed the specific neural mechanisms underlying the Poggendorff illusion induced by the real and the illusory contours, respectively. Left precentral gyrus and right middle occipital cortex were specifically involved in the Poggendorff illusion induced by the real contour. On the other hand, bilateral intraparietal sulcus (IPS) and right lateral occipital complex (LOC) were specifically involved in the Poggendorff illusion induced by the illusory contour. Functional implications of the above findings were further discussed.

  6. 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…

  7. 公路视错觉减速标线参数优化%Parameter optimization of highway optical illusion deceleration markings

    Institute of Scientific and Technical Information of China (English)

    刘浩学; 刘嘉; 赵炜华; 颜先华; 阎莹

    2011-01-01

    为提高道路危险路段运营安全水平,促使驾驶人主动降低车辆运行速度至安全范围,对比并优化了减速标线的形式及设计参数。依据人在动态环境下视错觉减速标线作用机理,对鱼刺形视错觉减速标线各设计参数进行分析和初选,并提出变间距减速标线相隔距离的计算方法。将不同设计参数进行组合,依据正交试验方案,利用仿真试验平台和实际道路试验,对比各种形式标线的实际减速效果。研究表明:不同设计参数的鱼刺形减速标线,其实际减速效果有很大差异,合理的参数设计方能产生良好的减速效果;与等间距标线相比,变间距减速标线的减速效果更优。%In order to improve the level of operation security in dangerous road sections,the speed should be slowed down to a safe range.The forms and design parameters of the deceleration markings was compared and optimized.Based on the mechanism of optical illusion deceleration markings in dynamic environment,the parameters of the chevron markings were analyzed and the space calculation method was proposed.The different design parameters were combined together to execute the orthogonal experiment.The simulation test and the actual road test were carried out to verify the actual deceleration effects.The results show that the actual deceleration is effected significantly by the design parameters,and good deceleration effects are subject to reasonable parameters design.The deceleration effects of variable spaced deceleration markings are better than the equal ones.

  8. 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...

  9. Creation of Ghost Illusions Using Metamaterials in Wave Dynamics

    CERN Document Server

    Jiang, Weixiang; Han, Tiancheng; Zhang, Shuang; Cui, Tiejun

    2013-01-01

    The creation of wave-dynamic illusion functionality is of great interests to various scientific communities, which can potentially transform an actual perception into the pre-controlled perception, thus empowering unprecedented applications in the advanced-material science, camouflage, cloaking, optical and/or microwave cognition, and defense security, etc. By using the space transformation theory and engineering capability of metamaterials, we propose and realize a functional ghost illusion device, which is capable of creating wave-dynamic virtual ghost images off the original object's position under the illumination of electromagnetic waves. The scattering signature of the object is thus ghosted and perceived as multiple ghost targets with different geometries and compositions. The ghost-illusion material, being inhomogeneous and anisotropic, was realized by thousands of varying unit cells working at non-resonance. The experimental demonstration of the ghost illusion validates our theory of scattering metam...

  10. Spatiotemporal cortical activation underlies the Müller-Lyer illusion: an event-related potentials study.

    Science.gov (United States)

    Zhang, Songyan; Du, Xue; Wu, Xin; Wei, Dongtao; Zhang, Meng; Qiu, Jiang

    2013-12-04

    Event-related brain potentials (ERPs) were used to examine the electrophysiological correlates of the visual illusion effect in the Müller-Lyer illusion tasks. The participants were presented with the context of a horizontal line with two symmetric inward-pointing arrowheads or outward-pointing arrowheads, and then, they were asked to indicate whether they perceived an increase or a decrease in the line length. The behavioral results showed that there were significant differences among the four types of tasks, which meant that participants could understand different mean illusion magnitudes. The ERP results showed that both the illusion-45 and the illusion-135 elicited a more negative ERP deflection (N180-280) than did the illusion-225 and illusion-315 between 180 and 280 ms. In addition, the strong illusion stimuli elicited a more positive ERP deflection (P280-450) than did the weak illusion stimuli between 280 and 450 ms after the onset of the stimuli. Dipole source analysis of the difference wave (illusion-135-illusion-225) indicated that one generator localized in the left lateral occipital cortex and the difference wave (illusion-45-illusion-135) indicated that one generator localized in the left lingual gyrus. Our results led us to conclude that the ERP deflection in the different illusory strength might be related to the theory of attention resource distribution or because of the inverse optics problem. Then, the early visual areas lateral occipital cortex and the lingual gyrus near to the visual cortex could contribute to integrated processing in the illusory contours and top-down control processing because of the visual experiences.

  11. 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.

  12. 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 rep...

  13. 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 ...... they want and what they can, the deviance perspective, we believe, also reduces the theoretical and normative biases, that characterises the discrimination and integration framework, and provide more reliable explanations. Key Words: Migration, Anomy, Norm-Divergence, Over-Education...

  14. The composite face illusion.

    Science.gov (United States)

    Murphy, Jennifer; Gray, Katie L H; Cook, Richard

    2017-04-01

    Few findings in cognitive science have proved as influential as the composite face effect. When the top half of one face is aligned with the bottom half of another, and presented upright, the resulting composite arrangement induces a compelling percept of a novel facial configuration. Findings obtained using composite face procedures have contributed significantly to our understanding of holistic face processing, the detrimental effects of face inversion, the development of face perception, and aberrant face perception in clinical populations. Composite paradigms continue to advance our knowledge of face perception, as exemplified by their recent use for investigating the perceptual mechanisms underlying dynamic face processing. However, the paradigm has been the subject of intense scrutiny, particularly over the last decade, and there is a growing sense that the composite face illusion, whilst easy to illustrate, is deceptively difficult to measure and interpret. In this review, we provide a focussed overview of the existing composite face literature, and identify six priorities for future research. Addressing these gaps in our knowledge will aid the evaluation and refinement of theoretical accounts of the illusion.

  15. 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.

  16. Homogeneous illusion device exhibiting transformed and shifted scattering effect

    Science.gov (United States)

    Mei, Jin-Shuo; Wu, Qun; Zhang, Kuang; He, Xun-Jun; Wang, Yue

    2016-06-01

    Based on the theory of transformation optics, a type of homogeneous illusion device exhibiting transformed and shifted scattering effect is proposed in this paper. The constitutive parameters of the proposed device are derived, and full-wave simulations are performed to validate the electromagnetic properties of transformed and shifted scattering effect. The simulation results show that the proposed device not only can visually shift the image of target in two dimensions, but also can visually transform the shape of target. It is expected that such homogeneous illusion device could possess potential applications in military camouflage and other field of electromagnetic engineering.

  17. 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 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...... a more fruitful theoretical and analytical framework than integration and discrimination. Taking departure in empirical evidence on immigrants’ preferences and behaviour as bounded rational actors, and how they actually articulate their everyday life practical experiences, including adjustment of what...

  18. 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.

  19. 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.

  20. The Star Wars Scroll Illusion

    Science.gov (United States)

    2015-01-01

    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. PMID:27648216

  1. Perceiving the present: systematization of illusions or illusion of systematization?

    Science.gov (United States)

    Briscoe, Robert E

    2010-11-01

    Mark Changizi et al. (2008) claim that it is possible systematically to organize more than 50 kinds of illusions in a 7 × 4 matrix of 28 classes. This systematization, they further maintain, can be explained by the operation of a single visual processing latency correction mechanism that they call "perceiving the present" (PTP). This brief report raises some concerns about the way a number of illusions are classified by the proposed systematization. It also poses two general problems-one empirical and one conceptual-for the PTP approach.

  2. Neglect's perspective on the Ponzo illusion.

    Science.gov (United States)

    Sedda, A; Ferrè, E R; Striemer, C L; Bottini, G

    2013-06-01

    Visual illusions have been used to explore implicit perception in neglect. Previous studies have highlighted differences between length and surface illusion perception in neglect, but much less is known about depth illusion perception. In the Ponzo illusion (a classic depth illusion), two converging oblique lines modulate the perceived length of two horizontal lines. In the current study, we presented modified versions of the Ponzo illusion in which only one of the converging oblique lines was presented (alternatively the right or the left one). This manipulation allowed us to explore (1) how acute patients with neglect process depth illusions, and (2) whether awareness of both converging lines is necessary for the full effect of the illusion. To examine these questions, we had participants (i.e. healthy controls, patients with neglect and right brain-damaged patients) to make a perceptual judgment regarding the perceived length of the upper versus lower horizontal line within the Ponzo frame in four conditions: (1) the classic Ponzo illusion, (2) a "modified left" Ponzo illusion with a single oblique line on the left, (3) a "modified right" Ponzo illusion with a single oblique line on the right and (4) a control condition with parallel lines. The results indicated that all participants perceived the canonical Ponzo illusion and the modified right illusion. Critically, patients with neglect did not perceive the modified left illusion. In addition, for neglect patients, there was no difference in the strength of the perceived illusion when comparing the canonical illusion with the modified right illusion. Importantly, single case analysis revealed a high degree of variability in the neglect group that seemed to be linked with the amount of damage to occipital areas. Overall our results indicate that: (1) the classic Ponzo illusion might be perceived in neglect patients based solely on perception of the right side of the stimulus configuration, and (2) differences

  3. Visual Illusion and Its Application%视错觉及其应用

    Institute of Scientific and Technical Information of China (English)

    马先兵; 孙水发; 夏平; 龚国强

    2012-01-01

    Vision is the most important way for human beings to obtain the external information. Owing to human own physical and psychological factors as well as the influences of the external factors, such as the light, shape, color and so forth, there will be an visual errors occurred, the errors also be named optical illusion. This paper systematically analyzes the various phenomenon or causes in visual illusion, as the result, visual illusion was divided into 5 categories: pathological illusion, dynamic illusion, geometry illusion, color illusion, contour illusion. On the basis of this, the paper introduces the vision illusion application, especially in image fusion realized in matlab.%视觉足人类获取外部信息的最重要方式。但由于人类自身的生理、心理因素以及外界光、形、色等因素的干扰,会产生视觉误差,即视错觉。本章系统的分析了视错觉产生原因,按不同的现象和成因把视错觉分成病理视错觉、动态视错觉、几何视错觉、颜色视错觉、轮廓错觉等5类。在此基础上介绍了视错觉的应用,特别介绍了其在图像融合中的应用,并用matlab实现了图像的融合。

  4. The Marble-Hand Illusion.

    Directory of Open Access Journals (Sweden)

    Irene Senna

    Full Text Available 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.

  5. Transformation magneto-statics and illusions for magnets

    OpenAIRE

    Fei Sun; Sailing He

    2014-01-01

    Based on the form-invariant of Maxwell’s equations under coordinate transformations, we extend the theoryof transformation optics to transformation magneto-statics, which can design magnets through coordinatetransformations. 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. Ourresearch will open a new door to designing magnets and controlling DC magnetic fields. ...

  6. Manifestations of Akiyoshi Kitaoka Motion Illusion Works%北冈明佳运动错视作品的表现形式

    Institute of Scientific and Technical Information of China (English)

    王云霞; 吴卫

    2013-01-01

    Akiyoshi Kitaoka, a famous Japanese master of optical illusion, whose motion illusion works create a strong sense of visual beauty by using different colours and light through careful arrangements. Motion illusion, a unique feature of Akiyoshi Kitaoka’s works, shows special optical illusion effects by incorporating various motion illusions in static pictures, which include rotatory visual illusions, fluctuating visual illusions, mobile visual illusions, and emission visual illusions.%日本著名错视大师北冈明佳创作的运动错视作品通过不同色彩和明度的运用,精心地排列和布局,创造出强烈的视幻之美。运动错觉是北冈明佳作品的一大特色,他将各种运动错觉展现在静态图片上,呈现出独特的视错觉效果,其运动错视包括旋转错视、波动错视、移动错视和发射错视4种表现形式。

  7. The elusive illusion: Do children (Homo sapiens) and capuchin monkeys (Cebus apella) see the Solitaire illusion?

    Science.gov (United States)

    Parrish, Audrey E; Agrillo, Christian; Perdue, Bonnie M; Beran, Michael J

    2016-02-01

    One approach to gaining a better understanding of how we perceive the world is to assess the errors that human and nonhuman animals make in perceptual processing. Developmental and comparative perspectives can contribute to identifying the mechanisms that underlie systematic perceptual errors often referred to as perceptual illusions. In the visual domain, some illusions appear to remain constant across the lifespan, whereas others change with age. From a comparative perspective, many of the illusions observed in humans appear to be shared with nonhuman primates. Numerosity illusions are a subset of visual illusions and occur when the spatial arrangement of stimuli within a set influences the perception of quantity. Previous research has found one such illusion that readily occurs in human adults, the Solitaire illusion. This illusion appears to be less robust in two monkey species, rhesus macaques and capuchin monkeys. We attempted to clarify the ontogeny of this illusion from a developmental and comparative perspective by testing human children and task-naïve capuchin monkeys in a computerized quantity judgment task. The overall performance of the monkeys suggested that they perceived the numerosity illusion, although there were large differences among individuals. Younger children performed similarly to the monkeys, whereas older children more consistently perceived the illusion. These findings suggest that human-unique perceptual experiences with the world might play an important role in the emergence of the Solitaire illusion in human adults, although other factors also may contribute.

  8. On the notion of visual illusions

    Directory of Open Access Journals (Sweden)

    Todorović Dejan

    2014-01-01

    Full Text Available The usual definitions of illusions, as incorrect perceptions or cases of discrepancies between reality and our perception of reality, have been criticized as inadequate. The reason is that it is not clear how to apply this notion in a number of interesting cases. This paper is an attempt to provide an adequate definition of illusions, appropriate for many classical phenomena usually referred to as illusions.

  9. “灰空间”中的视错觉表达%OPTICAL ILLUSIONS IN THE EXPRESSION OF "GRAY SPACE"

    Institute of Scientific and Technical Information of China (English)

    范哲

    2015-01-01

    视错觉通常被误认为是错误的知觉表达,“灰空间”则是一种多义化的空间定义,然而若将两者结合则能使空间产生意想不到的新奇感。本文通过这种新的认知方式来阐述“灰空间”的别样性,针对人们对“灰空间”的认知来介入视错觉的表达手法以及阐述它带来的功能性。%Optical ilusion is often deemed to the wrong expression of perception, and"gray space" is a definition of polysemy space, however, if you combine them, you can make the space produces unexpected novelty. This paper expounds the "gray space" of the new cognitive style, according to people's perception of "gray space" to intervene the expression of optical ilusion and expounds its functionality.

  10. Second-Order Footsteps Illusions

    Directory of Open Access Journals (Sweden)

    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.

  11. Bodily Illusions Modulate Tactile Perception

    OpenAIRE

    De Vignemont, Frédérique; H. Ehrsson, Henrik; Haggard, Patrick

    2005-01-01

    Touch differs from other exteroceptive senses in that the body itself forms part of the tactile percept. Interactions between proprioception and touch provide a powerful way to investigate the implicit body representation underlying touch. Here, we demonstrate that an intrinsic primary quality of a tactile object, for example its size, is directly affected by the perceived size of the body part touching it. We elicited proprioceptive illusions that the left index finger was either elongating ...

  12. Temporal processing characteristics of the Ponzo illusion.

    Science.gov (United States)

    Schmidt, Filipp; Haberkamp, Anke

    2016-03-01

    Many visual illusions result from assumptions of our visual system that are based on its long-term adaptation to our visual environment. Thus, visual illusions provide the opportunity to identify and learn about these fundamental assumptions. In this paper, we investigate the Ponzo illusion. Although many previous studies researched visual processing of the Ponzo illusion, only very few considered temporal processing aspects. However, it is well known that our visual percept is modulated by temporal factors. First, we used the Ponzo illusion as prime in a response priming task to test whether it modulates subsequent responses to the longer (or shorter) of two target bars. Second, we used the same stimuli in a perceptual task to test whether the Ponzo illusion is effective for very short presentation times (12 ms). We observed considerable priming effects that were of similar magnitude as those of a control condition. Moreover, the variations in the priming effects as a function of prime-target stimulus-onset asynchrony were very similar to that of the control condition. However, when analyzing priming effects as a function of participants' response speed, effects for the Ponzo illusion increased in slower responses. We conclude that although the illusion is established rapidly within the visual system, the full integration of context information is based on more time-consuming and later visual processing.

  13. "Madame Bovary": Illusion and Reality. [Lesson Plan].

    Science.gov (United States)

    Carangelo, Audrey

    Based on Gustave Flaubert's novel "Madame Bovary," this lesson plan presents activities designed to help students explore the theme of "illusion versus reality" in the novel; identify and list alternate themes in the novel; and cite specific examples of illusion versus reality from the novel. It includes objectives, materials, procedures,…

  14. [Sensory illusions in hang-gliding].

    Science.gov (United States)

    Bousquet, F; Bizeau, A; Resche-Rigon, P; Taillemite, J P; De Rotalier

    1997-01-01

    Sensory illusions in hang-gliding and para-gliding. Hang-gliding and para-gliding are at the moment booming sports. Sensory illusions are physiological phenomena sharing the wrong perception of the pilote's real position in space. These phenomena are very familiar to aeroplane pilotes, they can also be noticed on certain conditions with hang-gliding pilotes. There are many and various sensory illusions, but only illusions of vestibular origin will be dealt with in this article. Vestibular physiology is reminded with the working principle of a semicircular canal. Physiology and laws of physics explain several sensory illusions, especially when the pilote loses his visual landmarks: flying through a cloud, coriolis effect. Also some specific stages of hang-gliding foster those phenomena: spiraling downwards, self-rotation, following an asymetric closing of the parachute, spin on oneself. Therefore a previous briefing for the pilotes seems necessary.

  15. 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.

  16. Exploring the factors that encourage the illusions of control: the case of preventive illusions.

    Science.gov (United States)

    Blanco, Fernando; Matute, Helena

    2015-01-01

    Most previous research on illusions of control focused on generative scenarios, in which participants' actions aim to produce a desired outcome. By contrast, the illusions that may appear in preventive scenarios, in which actions aim to prevent an undesired outcome before it occurs, are less known. In this experiment, we studied two variables that modulate generative illusions of control, the probability with which the action takes place, P(A), and the probability of the outcome, P(O), in two different scenarios: generative and preventive. We found that P(O) affects the illusion in symmetrical, opposite directions in each scenario, while P(A) is positively related to the magnitude of the illusion. Our conclusion is that, in what concerns the illusions of control, the occurrence of a desired outcome is equivalent to the nonoccurrence of an undesired outcome, which explains why the P(O) effect is reversed depending on the scenario.

  17. Fun with maths and physics: brain teasers tricks illusions

    CERN Document Server

    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.

  18. 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

  19. Coral reef fish perceive lightness illusions

    Science.gov (United States)

    Simpson, Elisha E.; Marshall, N. Justin; Cheney, Karen L.

    2016-01-01

    Visual illusions occur when information from images are perceived differently from the actual physical properties of the stimulus in terms of brightness, size, colour and/or motion. Illusions are therefore important tools for sensory perception research and from an ecological perspective, relevant for visually guided animals viewing signals in heterogeneous environments. Here, we tested whether fish perceived a lightness cube illusion in which identical coloured targets appear (for humans) to return different spectral outputs depending on the apparent amount of illumination they are perceived to be under. Triggerfish (Rhinecanthus aculeatus) were trained to peck at coloured targets to receive food rewards, and were shown to experience similar shifts in colour perception when targets were placed in illusory shadows. Fish therefore appear to experience similar simultaneous contrast mechanisms to humans, even when targets are embedded in complex, scene-type illusions. Studies such as these help unlock the fundamental principles of visual system mechanisms. PMID:27748401

  20. 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.

  1. 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.

  2. [Perceived quality: illusion or perception].

    Science.gov (United States)

    Cárcamo, C R

    2011-01-01

    Patients as human beings determined by their structure cannot, while having an experience, distinguish between an illusion and reality, therefore they experience the different domains of existence and the different domains of reality. For them, the perception of service quality is experienced as a personal domain of reality, and this reality is a personal construction, generating as many realities as patients perceiving their experience with elements of their experience, whose distinctions that validate it are not necessarily shared or agreed. Health management must abandon the idea in that it is possible to build an objective quality service, to be able to make progress in building effective communication strategies and common consensus criteria for a quality service of distinction, in order to achieve effective satisfaction and patient loyalty.

  3. Creating illusion in computer aided performance

    OpenAIRE

    Marshall, Joe

    2009-01-01

    This thesis studies the creation of illusion in computer aided performance. Illusion is created here by using deceptions, and a design framework is presented which suggests several different deception strategies which may be useful. The framework has been developed in an iterative process in tandem with the development of 3 real world performances which were used to explore deception strategies. The first case study presents a system for augmenting juggling performance. The techniques tha...

  4. Elevator Illusion and Gaze Direction in Hypergravity

    Science.gov (United States)

    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.

  5. The tilt illusion: phenomenology and functional implications.

    Science.gov (United States)

    Clifford, Colin W G

    2014-11-01

    The perceived orientation of a line or grating is affected by the orientation structure of the surrounding image: the tilt illusion. Here, I offer a selective review of the literature on the tilt illusion, focusing on functional aspects. The review explores the merits of mechanistic accounts of the tilt illusion based upon sensory gain control in which neuronal responses are normalized by the pooled activity of other units. The role of inhibition between orientation-selective neurons is discussed, and it is argued that their associated disinhibition must also be taken into account in order to model the full angular dependence of the tilt illusion on surround orientation. Parallels are drawn with adaptation as modulation by the temporal rather than spatial context within which an image fragment is processed. The chromatic selectivity of the tilt illusion and the extent of its dependence on the visibility of the surround are used to infer characteristics of the neuronal normalization pools and the loci in the cortical processing hierarchy at which gain control operates. Finally, recent evidence is discussed as to the possible clinical relevance of the tilt illusion as a biomarker for schizophrenia.

  6. The time constant of the somatogravic illusion.

    Science.gov (United States)

    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.

  7. Spatial disorientation: more than just illusion.

    Science.gov (United States)

    Cheung, Bob

    2013-11-01

    Despite aggressive efforts in spatial disorientation (SD) research, hardware development, and training, the operational impact of SD in terms of crew and aircraft losses remains significant. Current training in spatial orientation is primarily composed of didactic lectures on the anatomy and physiology of the sensory systems. Significant efforts have been concentrated on reproducing various types of visual and vestibular "illusions" that pilots might encounter in flight, with limited and varying success. Unfortunately, the terms of "SD" and "illusion" have been used synonymously, leading to the general belief that if one were to be exposed to a specific type of illusion, one can prevent or avoid SD mishaps. Another setback is the inability of ground-based devices to reproduce the flight envelope. Often the demonstration of a specific illusion ends abruptly without further explanation or how these illusions can affect pilot performance. Demonstration of illusions seldom deals with the precipitating factors. We should provide pilots with skills to anticipate and assess the risk of SD during mission planning. Pilots should be sensitized to the physical and mental performance decrement during sensory conflicts and inadequacies. Recommendations should also be made on possible ways to recover from SD should they become disoriented. Special attention should be drawn to the properties of various flight displays that may contribute to SD. G tolerance and disorientation should be examined together in high performance aircraft as there is a close relationship between exposure to acceleration and maintaining orientation. The motto for counteracting SD is: anticipate, avoid, and counteract SD.

  8. Transformation optics and metamaterials

    Science.gov (United States)

    Chen, Huanyang; Chan, C. T.; Sheng, Ping

    2010-05-01

    Underpinned by the advent of metamaterials, transformation optics offers great versatility for controlling electromagnetic waves to create materials with specially designed properties. Here we review the potential of transformation optics to create functionalities in which the optical properties can be designed almost at will. This approach can be used to engineer various optical illusion effects, such as the invisibility cloak.

  9. A gestalt account of lightness illusions.

    Science.gov (United States)

    Gilchrist, Alan

    2014-01-01

    Illusions of lightness offer valuable clues to how lightness values are computed by the visual system. The traditional domain of lightness illusions must be expanded to include failures of constancy, as there is no distinction between these categories. Just as lightness is (relatively) constant in the face of changes in illumination level, so it is equally constant in the face of changes in background reflectance. Simultaneous lightness contrast, the most familiar lightness illusion, is fairly weak, and represents a failure of background-independent lightness constancy. It is argued that a combination of the highest-luminance rule of anchoring plus the Kardos idea of codetermination can account for most lightness illusions. Kardos suggested that the lightness value of a target surface is partly determined relative to the field of illumination (or framework) in which it is embedded, and partly relative to the neighboring field of illumination. Although Kardos did not apply his principle of codetermination to failures of background-independent constancy such as the simultaneous contrast illusion, this can be done rather easily by defining a framework as a perceptual group instead of identifying it strictly with an objective field of illumination.

  10. Moving Targets Virtually Via Composite Optical Transformation

    OpenAIRE

    Jiang, Wei Xiang; Cui, Tie Jun

    2009-01-01

    We propose a composite optical transformation to design an illusion device which can move the image of a target from one place to another place. Enclosed by such an illusion device, an arbitrary object located at one place appears to be at another place virtually. Different from the published shifted-position cloak which is composed of the left-handed materials with simultaneously negative permittivity and permeability, the illusion device proposed in this letter has positive permittivity and...

  11. Homo Novus - A Human Without Illusions

    CERN Document Server

    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.

  12. Illusion of Control in a Brownian Game

    CERN Document Server

    Satinover, J B

    2007-01-01

    Both single-player Parrondo games (SPPG) and multi-player Parrondo games (MPPG) display the Parrondo Effect (PE) wherein two or more individually fair (or Llosing) games yield a net winning outcome if alternated periodically or randomly. (There is a more formal, less restrictive definition of the PE.) We illustrate that, when subject to an elementary optimization rule, the PG displays degraded rather than enhanced returns. Optimization provides only the illusion of control, when low-entropy strategies (i.e. which use more information) under-perform random strategies (with maximal entropy). This illusion is unfortuntately widespread in many human attempts to manage or predict complex systems. For the PG, the illusion is especially striking in that the optimization rule reverses an already paradoxical-seeming positive gain - the Parrondo effect proper - and turns it negative. While this phenomenon has been previously demonstrated using somewhat artificial conditions in the MPPG (L. Dinios and J.M.R. Parrondo. E...

  13. Model of Illusions and Virtual Reality.

    Science.gov (United States)

    Gonzalez-Franco, Mar; Lanier, Jaron

    2017-01-01

    In Virtual Reality (VR) it is possible to induce illusions in which users report and behave as if they have entered into altered situations and identities. The effect can be robust enough for participants to respond "realistically," meaning behaviors are altered as if subjects had been exposed to the scenarios in reality. The circumstances in which such VR illusions take place were first introduced in the 80's. Since then, rigorous empirical evidence has explored a wide set of illusory experiences in VR. Here, we compile this research and propose a neuroscientific model explaining the underlying perceptual and cognitive mechanisms that enable illusions in VR. Furthermore, we describe the minimum instrumentation requirements to support illusory experiences in VR, and discuss the importance and shortcomings of the generic model.

  14. When is fiscal adjustment an illusion?

    NARCIS (Netherlands)

    Easterly, W; de Haan, J; Gali, G

    1999-01-01

    Fiscal adjustment is an illusion when it lowers the budget deficit or public debt but leaves government net worth unchanged. Conventional measures of the budget deficit largely show the change in public sector debt. Ideally, the measured deficit would reflect the change in Public sector net worth. M

  15. 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.

  16. Identity and Violence: The Illusion of Destiny

    Directory of Open Access Journals (Sweden)

    Prem Bahadur Chalaune

    2011-04-01

    Full Text Available Amartya Sen, (2006. Identity and Violence: The Illusion of Destiny. London: Penguin Books.( pp 215 Price: £ 14.99DOI: 10.3126/dsaj.v4i0.4525 Dhaulagiri Journal of Sociology and Anthropology Vol.4 2010 pp.261-268

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

    NARCIS (Netherlands)

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

    2008-01-01

    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

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

    NARCIS (Netherlands)

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

    2008-01-01

    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

  19. Learning with Animation and Illusions of Understanding

    Science.gov (United States)

    Paik, Eugene S.; Schraw, Gregory

    2013-01-01

    The illusion of understanding hypothesis asserts that, when people are learning with multimedia presentations, the addition of animation can affect metacognitive monitoring such that they perceive the presentation to be easier to understand and develop more optimistic metacomprehension. As a result, learners invest less cognitive effort when…

  20. 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

  1. When is fiscal adjustment an illusion?

    NARCIS (Netherlands)

    Easterly, W; de Haan, J; Gali, G

    Fiscal adjustment is an illusion when it lowers the budget deficit or public debt but leaves government net worth unchanged. Conventional measures of the budget deficit largely show the change in public sector debt. Ideally, the measured deficit would reflect the change in Public sector net worth.

  2. 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…

  3. Learning with Animation and Illusions of Understanding

    Science.gov (United States)

    Paik, Eugene S.; Schraw, Gregory

    2013-01-01

    The illusion of understanding hypothesis asserts that, when people are learning with multimedia presentations, the addition of animation can affect metacognitive monitoring such that they perceive the presentation to be easier to understand and develop more optimistic metacomprehension. As a result, learners invest less cognitive effort when…

  4. Multisensory Illusions and the Temporal Binding Window

    Directory of Open Access Journals (Sweden)

    Ryan A Stevenson

    2011-10-01

    Full Text Available The ability of our sensory systems to merge sensory information from distinct modalities is remarkable. One stimulus characteristic utilized in this operation is temporal coincidence. Auditory and visual information are integrated within a narrow range of temporal offsets, known as the temporal binding window (TBW, which varies between individuals, stimulus type, and task. In this series of experiments, we assessed the relationship within individuals between the width of their TBW and their ability to integrate audiovisual information. The TBW was measured through a perceived subjective simultaneity task. In conjunction with this, we measured each individual's ability to integrate auditory and visual information with two multisensory illusions, the McGurk effect and Flashbeep illusion. The results from these studies demonstrate that the TBW is highly correlated with the individual's ability to integrate. These relationships were seen in only the right TBW, in which visual presentations preceded auditory presentations, a finding that is ecologically logical. However, differences were seen between the two illusory conditions, where the McGurk effect was stronger in individuals with narrow TBWs, again, an ecologically logical finding. The opposite relationship was seen with flashbeep illusion, possibly due to inherent asynchronies in the illusion.

  5. [Workaholism: between illusion and addiction].

    Science.gov (United States)

    Elowe, J

    2010-09-01

    Workaholism surfaced some years ago as a veritable addiction in the wide sense of the term, dependence. It differs from other sorts of dependence in that it is very often viewed in a positive perspective in the sense that it conveys to the person concerned the illusion of well-being, as well as a motivation and dedication in their professional activity. During the past 30 years, several authors have attempted to define this concept and to determine its characteristics. Robinson believes that workaholics have an approach to life whereby their work feeds on time, energy and physical activity. This provokes consequences that affect their physical health and interpersonal relationships. They have a tendency to live in the future rather than in the present. For Scott, Moore and Micelli , the compulsion for work is not necessarily viewed as being detrimental to one's health. Spence and Robbins highlight the notion of the pleasure experienced at work in their theoretical approach. The prevalence of the dependence on work is estimated at between 27 and 30% in the general population. It is correlated to the number of hours of work per week and tends to be higher as annual revenue increases. The sex ratio is 1, and the parents of children 5 to 18 years of age are the most susceptible to considering themselves workaholics. The physical and psychological consequences of professional exhaustion are characterized primarily by the decrease in self-esteem, symptoms of fatigue, anxiety, depression, irritability and the manifestation of physical problems including cardiovascular ailments, as evidenced by hypertension, as well as heart and kidney complications. All the theoretical point of views, from the psychoanalytical models to the contemporary models, highlight self esteem as being the centerpiece of the question regarding the problem of workaholism. In fact, the narcissism articulated from the sociological evolution of our western way of life permits us to delineate the psychic

  6. 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.

  7. Remote sensing: A green illusion

    Science.gov (United States)

    Soudani, Kamel; François, Christophe

    2014-02-01

    An analysis reveals that satellite-observed increases in canopy greenness during dry seasons, which were previously interpreted as positive responses of Amazon forests to more sunlight, are in fact an optical artefact. See Letter p.221

  8. Eggs illusion: Local shape deformation generated by a grid pattern.

    Science.gov (United States)

    Qian, Kun; Mitsudo, Hiroyuki

    2016-12-01

    In this study, we report a new visual shape illusion, the eggs illusion, in which circular disks located at the midpoints between adjacent grid intersections are perceived as being deformed to ellipses. In Experiment 1, we examined the eggs illusion by using a matching method and found that grid luminance and patch size play a critical role in producing the illusory deformation. In Experiment 2, we employed several types of elliptic or circular patches to examine the conditions in which the illusory deformation was cancelled or weakened. We observed that the illusory deformation was dependent on local grid orientation. Based on these results, we found several common features between the eggs illusion and the scintillating grid illusion. This resemblance suggests a possibility that similar mechanisms underlie the two phenomena. In addition to the scintillating grid illusion, we also considered several known perceptual phenomena that might be related to the eggs illusion, i.e., the apparent size illusion, the shape-contrast effect, and the Orbison illusion. Finally, we discuss the role of orientation processing in generating the eggs illusion.

  9. Does the Ebbinghaus Illusion Affect Optimal Pointing?

    Directory of Open Access Journals (Sweden)

    M Lages

    2012-07-01

    Full Text Available We investigated speeded pointing movements (Trommershauser, Maloney, and Landy, 2003 in the presence of the Ebbinghaus illusion. Franz et al (2000 reported systematic effects of the Ebbinghaus illusion on grasping movements, contradicting earlier results (Aglioti, et al, 1995 and casting doubt on a strict dissociation between action and perception (Goodale and Milner, 1992. Here, we try to extend this finding by explicitly manipulating the consequence of motor actions in a speeded pointing task. We hypothesised that large, medium, and small circular surrounds induce the perception of smaller, unchanged, and larger target and penalty areas at the centre. If subjects take the visual illusion into account, then on average they should overshoot, hit, and undershoot the optimal point in the three illusion conditions, respectively. Subjects were asked to hit a circular target area on a touch screen with their right index finger. They were awarded +100 points for hitting the target, and in separate conditions either lost 0 or 500 points when touching an overlapping red penalty area. Feedback was provided at the end of each trial so the subjects could monitor their total score and gauge their performance. Participants were trained in 240 trials before performing the experiment in two blocks of 120 trials for each penalty condition with large, medium, and small surround stimuli randomly intermixed. Preliminary results from 12 observers indicate a significant effect of penalty on pointing position (F1,11=21.3, p=0.001 but no statistically significant effect for the Ebbinghaus illusion (F2,22=1.14, p=0.34. Results from a size adjustment task at the end of the experiment suggest that the perceived size of target and penalty area changed as predicted (large: −1.5, medium: 0.7, and small: 1.5 pixels but that the effect was too weak to systematically influence pointing. In conclusion, we found no clear evidence that the Ebbinghaus illusion can bias optimal

  10. Positive and negative affect in illusion of control

    OpenAIRE

    Novović Zdenka; Kovač Aleksandra; Đurić Veljko; Biro Mikloš

    2012-01-01

    Research regarding the illusion of control was dominated by the studies examining the effect of depressive affect on the overestimation of control over uncontrollable events. However, the relative contributions of high Negative Affect (NA) and low Positive Affect (PA), as underlying dimensions of depressive states, has remained unclear. This study researched how both PA and NA had affected the illusion of control. Two weeks before illusion induction, trait PA and NA of 54 first-year uni...

  11. Geometrical illusions are not always where you think they are

    Directory of Open Access Journals (Sweden)

    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

  12. Zen Mountains: An Illusion of Perceptual Transparency

    Directory of Open Access Journals (Sweden)

    Susan G. Wardle

    2015-04-01

    Full Text Available The human visual system is usually very successful in segmenting complex natural scenes. During a trip to the Nepalese Himalayas, we observed an impossible example of Nature's beauty: “transparent” mountains. The scene is captured in a photograph in which a pair of mountain peaks viewed in the far distance appear to be transparent. This illusion results from a fortuitous combination of lighting and scene conditions, which induce an erroneous integration of multiple segmentation cues. The illusion unites three classic principles of visual perception: Metelli's constraints for perceptual transparency, the Gestalt principle of good continuation, and depth from contrast and atmospheric scattering. This real-world “failure” of scene segmentation reinforces how ingeniously the human visual system typically integrates complex sources of perceptual information using heuristics based on likelihood as shortcuts to veridical perception.

  13. Zen Mountains: An Illusion of Perceptual Transparency

    OpenAIRE

    2015-01-01

    The human visual system is usually very successful in segmenting complex natural scenes. During a trip to the Nepalese Himalayas, we observed an impossible example of Nature's beauty: “transparent” mountains. The scene is captured in a photograph in which a pair of mountain peaks viewed in the far distance appear to be transparent. This illusion results from a fortuitous combination of lighting and scene conditions, which induce an erroneous integration of multiple segmentation cues. The illu...

  14. The Thatcher illusion in humans and monkeys.

    Science.gov (United States)

    Dahl, Christoph D; Logothetis, Nikos K; Bülthoff, Heinrich H; Wallraven, Christian

    2010-10-01

    Primates possess the remarkable ability to differentiate faces of group members and to extract relevant information about the individual directly from the face. Recognition of conspecific faces is achieved by means of holistic processing, i.e. the processing of the face as an unparsed, perceptual whole, rather than as the collection of independent features (part-based processing). The most striking example of holistic processing is the Thatcher illusion. Local changes in facial features are hardly noticeable when the whole face is inverted (rotated 180 degrees ), but strikingly grotesque when the face is upright. This effect can be explained by a lack of processing capabilities for locally rotated facial features when the face is turned upside down. Recently, a Thatcher illusion was described in the macaque monkey analogous to that known from human investigations. Using a habituation paradigm combined with eye tracking, we address the critical follow-up questions raised in the aforementioned study to show the Thatcher illusion as a function of the observer's species (humans and macaques), the stimulus' species (humans and macaques) and the level of perceptual expertise (novice, expert).

  15. Illusion of control in a Brownian game

    Science.gov (United States)

    Satinover, J. B.; Sornette, D.

    2007-12-01

    Both single-player Parrondo games (SPPG) and multi-player Parrondo games (MPPG) display the Parrondo effect (PE) wherein two or more individually fair (or losing) games yield a net winning outcome if alternated periodically or randomly. (There is a more formal, less restrictive definition of the PE.) We illustrate that, when subject to an elementary optimization rule, the PG displays degraded rather than enhanced returns. Optimization provides only the illusion of control, when low-entropy strategies (i.e., which use more information) under-perform random strategies (with maximal entropy). This illusion is unfortunately widespread in many human attempts to manage or predict complex systems. For the PG, the illusion is especially striking in that the optimization rule reverses an already paradoxical-seeming positive gain-the Parrondo effect proper-and turns it negative. While this phenomenon has been previously demonstrated using somewhat artificial conditions in the MPPG [L. Dinis, J.M.R. Parrondo, Europhys. Lett. 63 (2003) 319; J.M.R. Parrondo, L. Dinis, J. Buceta, K. Lindenberg, Advances in Condensed Matter and Statistical Mechanics, E. Korutcheva, R. Cuerno (Eds.), Nova Science Publishers, New York, 2003], we demonstrate it in the natural setting of a history-dependent SPPG.

  16. Brightness illusion in the guppy (Poecilia reticulata).

    Science.gov (United States)

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

    2016-02-01

    A long-standing debate surrounds the issue of whether human and nonhuman species share similar perceptual mechanisms. One experimental strategy to compare visual perception of vertebrates consists in assessing how animals react in the presence of visual illusions. To date, this methodological approach has been widely used with mammals and birds, while few studies have been reported in distantly related species, such as fish. In the present study we investigated whether fish perceive the brightness illusion, a well-known illusion occurring when 2 objects, identical in physical features, appear to be different in brightness. Twelve guppies (Poecilia reticulata) were initially trained to discriminate which rectangle was darker or lighter between 2 otherwise identical rectangles. Three different conditions were set up: neutral condition between rectangle and background (same background used for both darker and lighter rectangle); congruent condition (darker rectangle in a darker background and lighter rectangle in a lighter background); and incongruent condition (darker rectangle in a lighter background and lighter rectangle in a darker background). After reaching the learning criterion, guppies were presented with the illusory pattern: 2 identical rectangles inserted in 2 different backgrounds. Guppies previously trained to select the darker rectangle showed a significant choice of the rectangle that appears to be darker by human observers (and vice versa). The human-like performance exhibited in the presence of the illusory pattern suggests the existence of similar perceptual mechanisms between humans and fish to elaborate the brightness of objects.

  17. Ventral and dorsal stream interactions during the perception of the Müller-Lyer illusion: evidence derived from fMRI and dynamic causal modeling.

    Science.gov (United States)

    Plewan, Thorsten; Weidner, Ralph; Eickhoff, Simon B; Fink, Gereon R

    2012-10-01

    The human visual system converts identically sized retinal stimuli into different-sized perceptions. For instance, the Müller-Lyer illusion alters the perceived length of a line via arrows attached to its end. The strength of this illusion can be expressed as the difference between physical and perceived line length. Accordingly, illusion strength reflects how strong a representation is transformed along its way from a retinal image up to a conscious percept. In this study, we investigated changes of effective connectivity between brain areas supporting these transformation processes to further elucidate the neural underpinnings of optical illusions. The strength of the Müller-Lyer illusion was parametrically modulated while participants performed either a spatial or a luminance task. Lateral occipital cortex and right superior parietal cortex were found to be associated with illusion strength. Dynamic causal modeling was employed to investigate putative interactions between ventral and dorsal visual streams. Bayesian model selection indicated that a model that involved bidirectional connections between dorsal and ventral stream areas most accurately accounted for the underlying network dynamics. Connections within this network were partially modulated by illusion strength. The data further suggest that the two areas subserve differential roles: Whereas lateral occipital cortex seems to be directly related to size transformation processes, activation in right superior parietal cortex may reflect subsequent levels of processing, including task-related supervisory functions. Furthermore, the data demonstrate that the observer's top-down settings modulate the interactions between lateral occipital and superior parietal regions and thereby influence the effect of illusion strength.

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

    Science.gov (United States)

    Knol, Hester; Huys, Raoul; Sarrazin, Jean-Christophe; Jirsa, Viktor K

    2015-01-01

    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) 10% 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  20. No pain relief with the rubber hand illusion.

    Directory of Open Access Journals (Sweden)

    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.

  1. The Thatcher Illusion and Face Processing in Infancy

    Science.gov (United States)

    Bertin, Evelin; Bhatt, Ramesh S.

    2004-01-01

    Adults readily detect changes in face patterns brought about by the inversion of eyes and mouth when the faces are viewed upright but not when they are viewed upside down. Research suggests that this illusion (the Thatcher illusion) is caused by the interfering effects of face inversion on the processing of second-order relational information…

  2. Perceiving the Present and a Systematization of Illusions

    Science.gov (United States)

    Changizi, Mark A.; Hsieh, Andrew; Nijhawan, Romi; Kanai, Ryota; Shimojo, Shinsuke

    2008-01-01

    Over the history of the study of visual perception there has been great success at discovering countless visual illusions. There has been less success in organizing the overwhelming variety of illusions into empirical generalizations (much less explaining them all via a unifying theory). Here, this article shows that it is possible to…

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

    NARCIS (Netherlands)

    Barelds, Dick P. H.; Dijkstra, Pieternel

    2009-01-01

    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 Dutc

  4. 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

  5. The Function of the Illusions of Control and Freedom

    Science.gov (United States)

    Lefcourt, Herbert M.

    1973-01-01

    Argues that while freedom and control are both illusions, inventions of man to make sense of his experience, they do have consequences; and presents research evidence that the loss of the illusion of freedom may have untoward consequences for the way men live. (Author/JM)

  6. 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…

  7. Do Visual Illusions Probe the Visual Brain?: Illusions in Action without a Dorsal Visual Stream

    Science.gov (United States)

    Coello, Yann; Danckert, James; Blangero, Annabelle; Rossetti, Yves

    2007-01-01

    Visual illusions have been shown to affect perceptual judgements more so than motor behaviour, which was interpreted as evidence for a functional division of labour within the visual system. The dominant perception-action theory argues that perception involves a holistic processing of visual objects or scenes, performed within the ventral,…

  8. Do visual illusions probe the visual brain? Illusions in action without a dorsal visual stream.

    Science.gov (United States)

    Coello, Yann; Danckert, James; Blangero, Annabelle; Rossetti, Yves

    2007-04-09

    Visual illusions have been shown to affect perceptual judgements more so than motor behaviour, which was interpreted as evidence for a functional division of labour within the visual system. The dominant perception-action theory argues that perception involves a holistic processing of visual objects or scenes, performed within the ventral, inferior temporal cortex. Conversely, visuomotor action involves the processing of the 3D relationship between the goal of the action and the body, performed predominantly within the dorsal, posterior parietal cortex. We explored the effect of well-known visual illusions (a size-contrast illusion and the induced Roelofs effect) in a patient (IG) suffering bilateral lesions of the dorsal visual stream. According to the perception-action theory, IG's perceptual judgements and control of actions should rely on the intact ventral stream and hence should both be sensitive to visual illusions. The finding that IG performed similarly to controls in three different illusory contexts argues against such expectations and shows, furthermore, that the dorsal stream does not control all aspects of visuomotor behaviour. Assuming that the patient's dorsal stream visuomotor system is fully lesioned, these results suggest that her visually guided action can be planned and executed independently of the dorsal pathways, possibly through the inferior parietal lobule.

  9. Do Visual Illusions Probe the Visual Brain?: Illusions in Action without a Dorsal Visual Stream

    Science.gov (United States)

    Coello, Yann; Danckert, James; Blangero, Annabelle; Rossetti, Yves

    2007-01-01

    Visual illusions have been shown to affect perceptual judgements more so than motor behaviour, which was interpreted as evidence for a functional division of labour within the visual system. The dominant perception-action theory argues that perception involves a holistic processing of visual objects or scenes, performed within the ventral,…

  10. A real-life illusion of assimilation in the human face: eye size illusion caused by eyebrows and eye shadow.

    Science.gov (United States)

    Morikawa, Kazunori; Matsushita, Soyogu; Tomita, Akitoshi; Yamanami, Haruna

    2015-01-01

    Does an assimilative illusion like the Delboeuf illusion occur in the human face? We investigated factors that might influence the perceived size of the eyes in a realistic face. Experiment 1 manipulated the position of the eyebrows (high or low), the presence/absence of eye shadow, and the viewing distance (0.6 m or 5 m), then measured the perceived eye size using a psychophysical method. The results showed that low eyebrows (i.e., closer to the eyes) make the eyes appear larger, suggesting that the assimilation of eyes into the eyebrows is stronger when the eye-eyebrow distance is shorter. The results also demonstrated that the application of eye shadow also makes the eyes look larger. Moreover, the effect of eye shadow is more pronounced when viewed from a distance. In order to investigate the mechanism of the eye size illusion demonstrated in Experiment 1, Experiment 2 measured the magnitude of the Delboeuf illusion at a viewing distance of 0.6 m or 5 m, with or without gray gradation simulating the eye shadow that was used in Experiment 1. The experiment demonstrated that the Delboeuf illusion is modulated by viewing distance and gradation in the same way as the eye size illusion. These results suggest that the eye size illusion induced by the eyebrows and the Delboeuf illusion involve the same mechanism, and that eye shadow causes the assimilation of the eyes into itself and enhances assimilation between the eyes and the eyebrows.

  11. 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.

  12. The categories and research advances of visual illusions%视错觉现象的分类和研究进展

    Institute of Scientific and Technical Information of China (English)

    刘宏; 李哲媛; 许超

    2011-01-01

    视错觉指的是人或动物观察物体时,基于知觉经验或不当参照等形成的与客观事实不一致的特定感知.它能从独特的角度显示出视觉系统的认知功能和机理,因此研究错觉原理,建立合适的数学模型和计算机模拟模型,对心理学、生理学和计算机视觉等领域的发展有着重要的意义.在收集整理大量错觉图片的基础上,视错觉可按不同的现象和成因分为轮廓错觉、运动错觉、细胞群错觉、扭曲错觉、尺寸错觉和不可能图形等6类,其中典型错觉图片被选以介绍其成因和生理、心理、计算机领域的研究现状,阐述不同视错觉发生在视觉不同认知层次上,且拥有和正常视觉相同的神经基础,最后概述了视错觉现象的应用意义和前景.%When humans or animals observe things. visual/optical illusions can occur since the perceptions are sometimes inconsistent with realily and are caused by the ohservers ' experiences or improper references. Visual illusions can expose the cognitive functions and mechanisms of the human vision system from a unique perspective.Therefore, they help people to understand vision principles , to establish appropriate mathematical models and computer simulation models, and significantly promote the development of many research fields such as psychology,physiology, and computer vision. In this study, due to various phenomenon or causes, 620 illusory pictures were analyzed and divided into 6 eategories : contour illusions , motion illusions. cell-population illusions, distorted illusions, size illusions, and impossible objects/3-D illusions. Additionally, the causes and research status of typical illusions were presented. Furthermore, the conclusion was drawn that different illusions occur in different cognitive levels of the vision system and have the same neural basis as normal vision. Finally, the applications and research future were described.

  13. Neural Correlates of the Poggendorff Illusion Driven by Illusory Contour: An fMRI Study

    OpenAIRE

    Qi Chen; Li Li

    2011-01-01

    The Poggendorff illusion is a well-documented geometric illusion that involves the brain's perception of the interaction between oblique lines and object contours: an oblique line is apparently misaligned once interrupted by two parallel contours. This illusion occurs even when the parallel contours are defined subjectively or illusorily. In this fMRI study, we adopted a 4 (type of stimuli: Poggendorff illusion under real contour and its corresponding control condition; Poggendorff illusion u...

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

    Science.gov (United States)

    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.

  15. No pain relief with the rubber hand illusion.

    Science.gov (United States)

    Mohan, Rahul; Jensen, Karin B; 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.

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

    Science.gov (United States)

    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.

  17. Open active cloaking and illusion devices for the Laplace equation

    Science.gov (United States)

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

    2016-04-01

    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.

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

    Science.gov (United States)

    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.

  19. 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.

  20. 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

  1. Detecting Groupthink: Methods for Observing the Illusion of Unanimity.

    Science.gov (United States)

    Cline, Rebecca J. Welch

    1990-01-01

    Reconceptualizes groupthink symptoms as observable group interaction patterns. Proposes two coding systems for detecting the illusion of unanimity symptom, detecting both degree of unanimity and degree of the illusory versus substantive nature of that unanimity. (SR)

  2. Illusion versus Reality: Children's Understanding of Temperature Adaptation.

    Science.gov (United States)

    Arnold, Kevin D.; And Others

    1986-01-01

    Compares kindergartners' and third and sixth graders' understanding of an illusion reported by the philosopher John Locke, in which two hands simultaneously experience two different temperatures from a container of water at one temperature. (HOD)

  3. Orientation-sensitivity to facial features explains the Thatcher illusion.

    Science.gov (United States)

    Psalta, Lilia; Young, Andrew W; Thompson, Peter; Andrews, Timothy J

    2014-10-09

    The Thatcher illusion provides a compelling example of the perceptual cost of face inversion. The Thatcher illusion is often thought to result from a disruption to the processing of spatial relations between face features. Here, we show the limitations of this account and instead demonstrate that the effect of inversion in the Thatcher illusion is better explained by a disruption to the processing of purely local facial features. Using a matching task, we found that participants were able to discriminate normal and Thatcherized versions of the same face when they were presented in an upright orientation, but not when the images were inverted. Next, we showed that the effect of inversion was also apparent when only the eye region or only the mouth region was visible. These results demonstrate that a key component of the Thatcher illusion is to be found in orientation-specific encoding of the expressive features (eyes and mouth) of the face.

  4. Tony Kushner's "The Illusion" and Comedy's "Traversal of the Fantasy"

    National Research Council Canada - National Science Library

    Wolfe, Graham

    2011-01-01

    The author discusses Tony Kushner's "The Illusion," drawing upon the work of Slavoj Zizek and Alenka Zupancic, whose Lacan-inspired philosophy reflects the play's own fascination with the paradoxes...

  5. Positive illusions about a partner's personality and relationship quality

    NARCIS (Netherlands)

    Barelds, Dick P. H.; Dijkstra, Pieternel

    2011-01-01

    Previous studies have shown individuals to hold positive biases about their relationships. The present study examined positive illusions about a partner's specific personality characteristics in relation to relationship quality and personality. Both partners of 120 heterosexual couples participated

  6. The Müller-Lyer illusion in ant foraging.

    Science.gov (United States)

    Sakiyama, Tomoko; Gunji, Yukio-Pegio

    2013-01-01

    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.

  7. The Muller-Lyer illusion in ant foraging.

    Directory of Open Access Journals (Sweden)

    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.

  8. 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

  9. Positive illusions about a partner's personality and relationship quality

    NARCIS (Netherlands)

    Barelds, Dick P. H.; Dijkstra, Pieternel

    Previous studies have shown individuals to hold positive biases about their relationships. The present study examined positive illusions about a partner's specific personality characteristics in relation to relationship quality and personality. Both partners of 120 heterosexual couples participated

  10. 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.

  11. Alternative energies - the illusion and the facts

    Energy Technology Data Exchange (ETDEWEB)

    Schnell, P.

    1981-08-31

    Alternative eneriges and energy techniques are evaluated very differently from the point of view of their contribution to energy supply. The present article attempts to make a reasonable estimate of their possibilities and limits. It is found that, from the potenial inexhaustible energies, only a fraction can actually be utilised in a reasonable manner. Although it is an illusion - by wider utilisation of inexhaustible energies to dispense with nuclear energy also, in the long view a notable contribution is to be expected for world energy supply. The existing structures of the electricity economy in the Federal Republic of Germany offer adequate provision for an initial exploitation of the, here severely limited, potential of inexhaustible energies.

  12. A moving-barber-pole illusion.

    Science.gov (United States)

    Sun, Peng; Chubb, Charles; Sperling, George

    2014-05-01

    In the barber-pole illusion (BPI), a diagonally moving grating is perceived as moving vertically because of the shape of the vertically oriented window through which it is viewed-a strong shape-motion interaction. We introduce a novel stimulus-the moving barber pole-in which a diagonal, drifting sinusoidal carrier is windowed by a raised, vertical, drifting sinusoidal modulator that moves independently of the carrier. In foveal vision, the moving-barber-pole stimulus can be perceived as several active barber poles drifting horizontally but also as other complex dynamic patterns. In peripheral vision, pure vertical motion (the moving-barber-pole illusion [MBPI]) is perceived for a wide range of conditions. In foveal vision, the MBPI is observed, but only when the higher-order modulator motion is masked. Theories to explain the BPI make indiscriminable predictions in a standard barber-pole display. But, in moving-barber-pole stimuli, the motion directions of features (e.g., end stops) of the first-order carrier and of the higher-order modulator are all different from the MBPI. High temporal frequency stimuli viewed peripherally greatly reduce the effectiveness of higher-order motion mechanisms and, ideally, isolate a single mechanism responsible for the MBPI. A three-stage motion-path integration mechanism that (a) computes local motion energies, (b) integrates them for a limited time period along various spatial paths, and (c) selects the path with the greatest motion energy, quantitatively accounts for these high-frequency data. The MBPI model also accounts for the perceived motion-direction in peripherally viewed moving-barber-pole stimuli that do and do not exhibit the MBPI over the entire range of modulator (0-10 Hz) and carrier (2.5-10 Hz) temporal frequencies tested.

  13. The building blocks of the full body ownership illusion

    Directory of Open Access Journals (Sweden)

    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

  14. An Experimental Research on Causal Illusion (in Chinese)

    OpenAIRE

    Shao, Z. F.; Zhao, J.

    2004-01-01

    The research examined humans’ causal attribution of response-outcome under controllable and uncontrollable conditions respectively and attempted to find out whether providing appropriate external cues could be beneficial to them in making accurate judgments. The results indicate: 1) under controllable conditions, the delay of feedback might lead to causal illusion; 2) under uncontrollable conditions, the subjects developed superstition and illusion of control rather than helplessness; 3) prov...

  15. Vertical-horizontal illusion: one eye is better than two.

    Science.gov (United States)

    Prinzmetal, W; Gettleman, L

    1993-01-01

    The vertical-horizontal illusion is the tendency for observers to overestimate the length of a vertical line relative to a horizontal line that has the same length. One explanation of this illusion is that the visual field is elongated in the horizontal direction, and that the vertical-horizontal illusion is a kind of framing effect (Künnapas, 1957a, 1957b, 1957c). Since the monocular visual field is less asymmetric than the combined visual field, this theory predicts that the illusion should be reduced with monocular presentation. This prediction was tested in five experiments, in which the vertical-horizontal illusion was examined in a variety of situations--including observers seated upright versus reclined 90 degrees, monocular presentation with the dominant versus the nondominant eye, viewing in the dark versus in the light, and viewing with asymmetrical frames of reference. The illusion was reliably reduced with monocular presentation under conditions that affected the asymmetry of the phenomenal visual field.

  16. The Emergence of Figural Effects in the Watercolor Illusion

    Science.gov (United States)

    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.

  17. Information processing correlates of a size-contrast illusion

    Directory of Open Access Journals (Sweden)

    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.

  18. Seeing Is the Hardest Thing to See: Using Illusions to Teach Visual Perception

    Science.gov (United States)

    Riener, Cedar

    2015-01-01

    This chapter describes three examples of using illusions to teach visual perception. The illusions present ways for students to change their perspective regarding how their eyes work and also offer opportunities to question assumptions regarding their approach to knowledge.

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

    OpenAIRE

    Orgaz, Cristina; Estévez, Ana; Matute, Helena

    2013-01-01

    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 asso...

  20. Time course of the effect of the Muller-Lyer illusion on saccades and perceptual judgments

    OpenAIRE

    Brouwer, A.J. de; Brenner, E.; Medendorp, W. P.; Smeets, J. B. J.

    2014-01-01

    The amplitude of saccadic eye movements is affected by size illusions such as the Muller-Lyer illusion, but this effect varies highly between studies. Here we examine the origin of this variability by testing the influence of three temporal factors on the effect of the Muller-Lyer illusion: presentation time, response delay, and saccade latency. Subjects performed reflexive saccades, deferred saccades, and memory-guided saccades along the shaft of the illusion. We evaluated the time course of...

  1. Rubber hand illusion affects joint angle perception.

    Directory of Open Access Journals (Sweden)

    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.

  2. Overdistribution illusions: Categorical judgments produce them, confidence ratings reduce them.

    Science.gov (United States)

    Brainerd, C J; Nakamura, K; Reyna, V F; Holliday, R E

    2017-01-01

    Overdistribution is a form of memory distortion in which an event is remembered as belonging to too many episodic states, states that are logically or empirically incompatible with each other. We investigated a response formatting method of suppressing 2 basic types of overdistribution, disjunction and conjunction illusions, which parallel some classic illusions in the judgment and decision making literature. In this method, subjects respond to memory probes by rating their confidence that test cues belong to specific episodic states (e.g., presented on List 1, presented on List 2), rather than by making the usual categorical judgments about those states. The central prediction, which was derived from the task calibration principle of fuzzy-trace theory, was that confidence ratings should reduce overdistribution by diminishing subjects' reliance on noncompensatory gist memories. The data of 3 experiments agreed with that prediction. In Experiment 1, there were reliable disjunction illusions with categorical judgments but not with confidence ratings. In Experiment 2, both response formats produced reliable disjunction illusions, but those for confidence ratings were much smaller than those for categorical judgments. In Experiment 3, there were reliable conjunction illusions with categorical judgments but not with confidence ratings. Apropos of recent controversies over confidence-accuracy correlations in memory, such correlations were positive for hits, negative for correct rejections, and the 2 types of correlations were of equal magnitude. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  3. Directional organization and shape formation: new illusions and Helmholtz's Square.

    Science.gov (United States)

    Pinna, Baingio

    2015-01-01

    According to Helmholtz's Square illusion, a square appears wider when it is filled with vertical lines and higher when filled with horizontal lines (Helmholtz von, 1866). Recently, Pinna (2010a) demonstrated that the grouping of small squares on the basis of the similarity principle influences also perception of their shape and of the whole emerging shapes. The direction imparted by grouping is the main attribute that influences the shape by polarizing it in the same direction both globally and locally. The rectangle illusion is opposite to what expected on the basis of Helmholtz's Square illusion. Aim of this work is to solve the antinomy between the two sets of illusions and to demonstrate a common explanation based on the interaction between different sources of directional organization. This was accomplished by introducing some new phenomena and through phenomenological experiments proving the role played by the directional shape organization in shape formation. According to our results, Helmholtz's square illusion shows at least two synergistic sources of directional organization: the direction of the grouping of the lines due to their similarity of the luminance contrast and the direction of the grouping of the lines due to the good continuation.

  4. Subjective illusion of control modulates striatal reward anticipation in adolescence.

    Science.gov (United States)

    Lorenz, Robert C; Gleich, Tobias; Kühn, Simone; Pöhland, Lydia; Pelz, Patricia; Wüstenberg, Torsten; Raufelder, Diana; Heinz, Andreas; Beck, Anne

    2015-08-15

    The perception of control over the environment constitutes a fundamental biological adaptive mechanism, especially during development. Previous studies comparing an active choice condition with a passive no-choice condition showed that the neural basis of this mechanism is associated with increased activity within the striatum and the prefrontal cortex. In the current study, we aimed to investigate whether subjective belief of control in an uncertain gambling situation induces elevated activation in a cortico-striatal network. We investigated 79 adolescents (age range: 13-16years) during reward anticipation with a slot machine task using functional magnetic resonance imaging. We assessed post-experimentally whether the participants experienced a subjective illusion of control on winning or losing in this task that was objectively not given. Nineteen adolescents experienced an illusion of control during slot machine gambling. This illusion of control group showed an increased neural activity during reward anticipation within a cortico-striatal network including ventral striatum (VS) as well as right inferior frontal gyrus (rIFG) relative to the group reporting no illusion of control. The rIFG activity was inversely associated with impulsivity in the no illusion of control group. The subjective belief about control led to an elevated ventral striatal activity, which is known to be involved in the processing of reward. This finding strengthens the notion that subjectively perceived control, not necessarily the objective presence of control, affects striatal reward-related processing.

  5. Illusions of causality at the heart of pseudoscience.

    Science.gov (United States)

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

    2011-08-01

    Pseudoscience, superstitions, and quackery are serious problems that threaten public health and in which many variables are involved. Psychology, however, has much to say about them, as it is the illusory perceptions of causality of so many people that needs to be understood. The proposal we put forward is that these illusions arise from the normal functioning of the cognitive system when trying to associate causes and effects. Thus, we propose to apply basic research and theories on causal learning to reduce the impact of pseudoscience. We review the literature on the illusion of control and the causal learning traditions, and then present an experiment as an illustration of how this approach can provide fruitful ideas to reduce pseudoscientific thinking. The experiment first illustrates the development of a quackery illusion through the testimony of fictitious patients who report feeling better. Two different predictions arising from the integration of the causal learning and illusion of control domains are then proven effective in reducing this illusion. One is showing the testimony of people who feel better without having followed the treatment. The other is asking participants to think in causal terms rather than in terms of effectiveness. ©2010 The British Psychological Society.

  6. The cutaneous rabbit illusion affects human primary sensory cortex somatotopically.

    Directory of Open Access Journals (Sweden)

    Felix Blankenburg

    2006-03-01

    Full Text Available We used functional magnetic resonance imaging (fMRI to study neural correlates of a robust somatosensory illusion that can dissociate tactile perception from physical stimulation. Repeated rapid stimulation at the wrist, then near the elbow, can create the illusion of touches at intervening locations along the arm, as if a rabbit hopped along it. We examined brain activity in humans using fMRI, with improved spatial resolution, during this version of the classic cutaneous rabbit illusion. As compared with control stimulation at the same skin sites (but in a different order that did not induce the illusion, illusory sequences activated contralateral primary somatosensory cortex, at a somatotopic location corresponding to the filled-in illusory perception on the forearm. Moreover, the amplitude of this somatosensory activation was comparable to that for veridical stimulation including the intervening position on the arm. The illusion additionally activated areas of premotor and prefrontal cortex. These results provide direct evidence that illusory somatosensory percepts can affect primary somatosensory cortex in a manner that corresponds somatotopically to the illusory percept.

  7. 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.

  8. Source illusion devices for flexural Lamb waves using elastic metasurfaces

    CERN Document Server

    Liu, Yongquan; Liu, Fu; Diba, Owen; Lamb, Alistair; Li, Jensen

    2016-01-01

    Metamaterials with the transformation method has greatly promoted the development in achieving invisibility and illusion for various classical waves. However, the requirement of tailor-made bulk materials and extreme constitutive parameters associated to illusion designs hampers its further progress. 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 metasurfaces for shifting, transforming and splitting a point source with "space-coiling" structures. The effects are found to be broadband and robust against a change of source position, with agreement from numerical simulations and Huygens-Fresnel theory. The proposed approach provides an avenue to generically manipulate guided elastic waves in solids, and is...

  9. Understanding human perception by human-made illusions.

    Science.gov (United States)

    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.

  10. Effect of flanking sounds on the auditory continuity illusion.

    Directory of Open Access Journals (Sweden)

    Maori Kobayashi

    Full Text Available BACKGROUND: The auditory continuity illusion or the perceptual restoration of a target sound briefly interrupted by an extraneous sound has been shown to depend on masking. However, little is known about factors other than masking. METHODOLOGY/PRINCIPAL FINDINGS: We examined whether a sequence of flanking transient sounds affects the apparent continuity of a target tone alternated with a bandpass noise at regular intervals. The flanking sounds significantly increased the limit of perceiving apparent continuity in terms of the maximum target level at a fixed noise level, irrespective of the frequency separation between the target and flanking sounds: the flanking sounds enhanced the continuity illusion. This effect was dependent on the temporal relationship between the flanking sounds and noise bursts. CONCLUSIONS/SIGNIFICANCE: The spectrotemporal characteristics of the enhancement effect suggest that a mechanism to compensate for exogenous attentional distraction may contribute to the continuity illusion.

  11. Humans are not fooled by size illusions in attractiveness judgements.

    Science.gov (United States)

    Bateson, Melissa; Tovée, Martin J; George, Hannah R; Gouws, Anton; Cornelissen, Piers L

    2014-03-01

    Could signallers use size contrast illusions to dishonestly exaggerate their attractiveness to potential mates? Using composite photographs of women from three body mass index (BMI) categories designed to simulate small groups, we show that target women of medium size are judged as thinner when surrounded by larger women than when surrounded by thinner women. However, attractiveness judgements of the same target women were unaffected by this illusory change in BMI, despite small true differences in the BMIs of the target women themselves producing strong effects on attractiveness. Thus, in the context of mate choice decisions, the honesty of female body size as a signal of mate quality appears to have been maintained by the evolution of assessment strategies that are immune to size contrast illusions. Our results suggest that receiver psychology is more flexible than previously assumed, and that illusions are unlikely to drive the evolution of exploitative neighbour choice in human sexual displays.

  12. Binocular disparity as an explanation for the moon illusion

    CERN Document Server

    Antonides, Joseph

    2013-01-01

    We present another explanation for the moon illusion, in which the moon looks larger near the horizon than near the zenith. In our model, the sky is considered a spatially contiguous and geometrically smooth surface. When an object (like the moon) breaks the contiguity of the surface, humans perceive an occlusion of the surface rather than an object appearing through a hole. Binocular vision dictates that the moon is distant, but this perception model dictates that the moon is closer than the sky. To solve the dilemma, the brain distorts the projections of the moon to increase the binocular disparity, which results in increase of the angular size of the moon. The degree of the distortion depends upon the apparent distance to the sky, which is influenced by the surrounding objects and the condition of the sky. The closer the sky appears, the stronger the illusion. At the zenith, few distance cues are present, causing difficulty with distance estimation and weakening the illusion.

  13. Three-dimensional visual illusion of graphic painting

    Institute of Scientific and Technical Information of China (English)

    于静

    2012-01-01

    Visual illusion is the visual design of a special category.It is a set of technology and art in one of a unique form of artistic expression.Visual illusion can give people a taste of the spirit, with strong cultural con- tent and artistic appeal.So by this way of painting, it has a clever and unique perspective. Aspect If the plane can be realistic paintings to life, then the three-dimensional, two-dimensional space can be called even more powerful by aspects.

  14. 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.

  15. The "motion silencing" illusion results from global motion and crowding.

    Science.gov (United States)

    Turi, Marco; Burr, David

    2013-04-18

    Suchow and Alvarez (2011) recently devised a striking illusion, where objects changing in color, luminance, size, or shape appear to stop changing when they move. They refer to the illusion as "motion silencing of awareness to visual change." Here we present evidence that the illusion results from two perceptual processes: global motion and crowding. We adapted Suchow and Alvarez's stimulus to three concentric rings of dots, a central ring of "target dots" flanked on either side by similarly moving flanker dots. Subjects had to identify in which of two presentations the target dots were continuously changing (sinusoidally) in size, as distinct from the other interval in which size was constant. The results show: (a) Motion silencing depends on target speed, with a threshold around 0.2 rotations per second (corresponding to about 10°/s linear motion). (b) Silencing depends on both target-flanker spacing and eccentricity, with critical spacing about half eccentricity, consistent with Bouma's law. (c) The critical spacing was independent of stimulus size, again consistent with Bouma's law. (d) Critical spacing depended strongly on contrast polarity. All results imply that the "motion silencing" illusion may result from crowding.

  16. Social misdirection fails to enhance a magic illusion.

    Science.gov (United States)

    Cui, Jie; Otero-Millan, Jorge; Macknik, Stephen L; King, Mac; Martinez-Conde, Susana

    2011-01-01

    Visual, multisensory and cognitive illusions in magic performances provide new windows into the psychological and neural principles of perception, attention, and cognition. We investigated a magic effect consisting of a coin "vanish" (i.e., the perceptual disappearance of a coin after a simulated toss from hand to hand). Previous research has shown that magicians can use joint attention cues such as their own gaze direction to strengthen the observers' perception of magic. Here we presented naïve observers with videos including real and simulated coin tosses to determine if joint attention might enhance the illusory perception of simulated coin tosses. The observers' eye positions were measured, and their perceptual responses simultaneously recorded via button press. To control for the magician's use of joint attention cues, we occluded his head in half of the trials. We found that subjects did not direct their gaze at the magician's face at the time of the coin toss, whether the face was visible or occluded, and that the presence of the magician's face did not enhance the illusion. Thus, our results show that joint attention is not necessary for the perception of this effect. We conclude that social misdirection is redundant and possibly detracting to this very robust sleight-of-hand illusion. We further determined that subjects required multiple trials to effectively distinguish real from simulated tosses; thus the illusion was resilient to repeated viewing.

  17. Face Processing at Birth: A Thatcher Illusion Study

    Science.gov (United States)

    Leo, Irene; Simion, Francesca

    2009-01-01

    The present study was aimed at exploring newborns' ability to recognize configural changes within real face images by testing newborns' sensitivity to the Thatcher illusion. Using the habituation procedure, newborns' ability to discriminate between an unaltered face image and the same face with the eyes and the mouth 180 degrees rotated (i.e.…

  18. 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

  19. Mathematics Induction in School; An Illusion of Rigor.

    Science.gov (United States)

    Lowenthal, Francis; Eisenberg, Theodore

    1992-01-01

    Discusses the mathematical, philosophical, and pedagogical problems in the theorem of mathematical induction. Argues that mathematical induction is a meta-theorem, that is a theorem within a theorem, whose pitfalls and illusions of rigor should be discussed before implementation into the school curriculum. (MDH)

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

    NARCIS (Netherlands)

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

    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

  1. Trend of Average Wages as Indicator of Hypothetical Money Illusion

    Directory of Open Access Journals (Sweden)

    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.

  2. Social Misdirection Fails to Enhance a Magic Illusion

    Science.gov (United States)

    Cui, Jie; Otero-Millan, Jorge; Macknik, Stephen L.; King, Mac; Martinez-Conde, Susana

    2011-01-01

    Visual, multisensory and cognitive illusions in magic performances provide new windows into the psychological and neural principles of perception, attention, and cognition. We investigated a magic effect consisting of a coin “vanish” (i.e., the perceptual disappearance of a coin after a simulated toss from hand to hand). Previous research has shown that magicians can use joint attention cues such as their own gaze direction to strengthen the observers’ perception of magic. Here we presented naïve observers with videos including real and simulated coin tosses to determine if joint attention might enhance the illusory perception of simulated coin tosses. The observers’ eye positions were measured, and their perceptual responses simultaneously recorded via button press. To control for the magician’s use of joint attention cues, we occluded his head in half of the trials. We found that subjects did not direct their gaze at the magician’s face at the time of the coin toss, whether the face was visible or occluded, and that the presence of the magician’s face did not enhance the illusion. Thus, our results show that joint attention is not necessary for the perception of this effect. We conclude that social misdirection is redundant and possibly detracting to this very robust sleight-of-hand illusion. We further determined that subjects required multiple trials to effectively distinguish real from simulated tosses; thus the illusion was resilient to repeated viewing. PMID:22046155

  3. 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 indivi

  4. Proprioceptive movement illusions due to prolonged stimulation: reversals and aftereffects.

    Directory of Open Access Journals (Sweden)

    Tatjana Seizova-Cajic

    Full Text Available BACKGROUND: Adaptation to constant stimulation has often been used to investigate the mechanisms of perceptual coding, but the adaptive processes within the proprioceptive channels that encode body movement have not been well described. We investigated them using vibration as a stimulus because vibration of muscle tendons results in a powerful illusion of movement. METHODOLOGY/PRINCIPAL FINDINGS: We applied sustained 90 Hz vibratory stimulation to biceps brachii, an elbow flexor and induced the expected illusion of elbow extension (in 12 participants. There was clear evidence of adaptation to the movement signal both during the 6-min long vibration and on its cessation. During vibration, the strong initial illusion of extension waxed and waned, with diminishing duration of periods of illusory movement and occasional reversals in the direction of the illusion. After vibration there was an aftereffect in which the stationary elbow seemed to move into flexion. Muscle activity shows no consistent relationship with the variations in perceived movement. CONCLUSION: We interpret the observed effects as adaptive changes in the central mechanisms that code movement in direction-selective opponent channels.

  5. The continuous Wagon Wheel Illusion is object-based.

    Science.gov (United States)

    VanRullen, Rufin

    2006-11-01

    The occurrence of perceived reversed motion while observers view a periodic, continuously moving stimulus (the "continuous Wagon Wheel Illusion") has been taken as evidence that some aspects of motion perception rely on discrete sampling of visual information. The spatial extent of this sampling is currently under debate. When two separate motion stimuli are viewed simultaneously, the illusion of reversed motion rarely occurs for both objects together: this rules out global sampling of the visual field. The same result holds when the objects are superimposed by transparency: this argues against location-based sampling. Here we show that the sampling is in fact object-based: we use a rotating ring stimulus split in two halves. When the two halves move in opposite directions, appearing to belong to separate objects, perceptual reversals occur in either half at a time, but rarely in both. When the two halves physically move in compatible directions, they generally appear to reverse simultaneously: the illusion keeps the perceptual object united. Rather than the local low-level properties of the motion stimulus (which are comparable in both cases), it is thus the high-level organization of the scene that determines the extent of perceived motion reversals. These results imply that the continuous Wagon Wheel Illusion, and any discrete perceptual sampling that may cause it, is restricted to the object of our attention.

  6. Social misdirection fails to enhance a magic illusion

    Directory of Open Access Journals (Sweden)

    Jie eCui

    2011-09-01

    Full Text Available Visual, multisensory and cognitive illusions in magic performances provide new windows into the psychological and neural principles of perception, attention and cognition. We investigated a magic effect consisting of a coin vanish (i.e. the perceptual disappearance of a coin after a simulated toss from hand to hand. Previous research has shown that magicians can use joint attention cues such as their own gaze direction to strengthen the observers’ perception of magic. Here we presented naïve observers with videos including real and simulated coin tosses to determine if joint attention might enhance the illusory perception of simulated coin tosses. The observers’ eye positions were measured, and their perceptual responses simultaneously recorded via button press. To control for the magician’s use of joint attention cues, we occluded his head in half of the trials. We found that subjects did not direct their gaze at the magician’s face at the time of the coin toss, whether the face was visible or occluded, and that the presence of the magician’s face did not enhance the illusion. Thus, our results show that joint attention is not necessary for the perception of this effect. We conclude that social misdirection is redundant and possibly detracting to this very robust sleight-of-hand illusion. We further determined that subjects required multiple trials to effectively distinguish real from simulated tosses; thus the illusion was resilient to repeated viewing.

  7. 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...

  8. An ordinal model of the McGurk illusion

    DEFF Research Database (Denmark)

    Andersen, Tobias

    2011-01-01

    an ordinal model, in which the response categories are ordered cyclically, that can account for the McGurk illusion. We compare this model to the Fuzzy Logical Model of Perception (FLMP), which is not an ordinal model, based on an original data set. While the FLMP fitted the data better than the ordinal...

  9. 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 du

  10. Geometrical illusions are not always where you think they are: a review of some classical and less classical illusions, and ways to describe them.

    Science.gov (United States)

    Ninio, Jacques

    2014-01-01

    Geometrical illusions are known through a small core of classical illusions that were discovered in the second half of the nineteenth 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 twentieth 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. 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 fish). 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 varies with its orientation in the plane). We showed first that the Zöllner illusion already exists at the level of single stacks, and that it does not amount to a rotation of the stacks. Later work suggested that it is best described by an "orthogonal expansion

  11. Quadri-stability of a spatially ambiguous auditory illusion

    Directory of Open Access Journals (Sweden)

    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

  12. Asymmetric effects of luminance and chrominance in the watercolor illusion

    Directory of Open Access Journals (Sweden)

    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.

  13. 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.

  14. The Moses, mega-Moses, and Armstrong illusions: integrating language comprehension and semantic memory.

    Science.gov (United States)

    Shafto, M; MacKay, D G

    2000-09-01

    This study develops a new theory of the Moses illusion, observed in responses to general knowledge questions such as, "How many animals of each kind did Moses take on the Ark?" People often respond "two" rather than "zero" despite knowing that Noah, not Moses, launched the Ark. Our theory predicted two additional types of conceptual error demonstrated here: the Armstrong and mega-Moses illusions. The Armstrong illusion involved questions resembling, "What was the famous line uttered by Louis Armstrong when he first set foot on the moon?" People usually comprehend such questions as valid, despite knowing that Louis Armstrong was a jazz musician who never visited the moon. This Armstrong illusion was not due to misperceiving the critical words (Louis Armstrong), and occurred as frequently as the Moses illusion (with critical words embedded in identical sentential contexts), but less frequently than the mega-Moses illusion caused when Moses and Armstrong factors were combined.

  15. Factors affecting the haptic filled-space illusion for dynamic touch.

    Science.gov (United States)

    Sanders, Abram F J; Kappers, Astrid M L

    2009-02-01

    In the haptic filled-space illusion for active dynamic touch, observers move their fingertip across an unfilled extent or an extent filled with intermediate stimulations. Previous researchers have reported lengths of filled extents to be overestimated, but the parameters affecting the strength of the illusion are still largely unknown. In the current research, we show that the illusion persists when intermediate stimulations do not provide information about the extent's length. In addition, the results show that the strength of the illusion increases with the number of filler elements. In contrast with earlier research, we control for movement speed differences between filled and unfilled extents. The results suggest that the strength of the illusion is independent of the overall average movement speed. Insight into factors affecting the strength of the illusion may provide a better understanding of the kinematic mechanisms underlying haptic length perception.

  16. Cortical responses to the mirror box illusion: a high-resolution EEG study.

    Science.gov (United States)

    Egsgaard, Line Lindhardt; Petrini, Laura; Christoffersen, Giselle; Arendt-Nielsen, Lars

    2011-12-01

    The mirror box illusion has proven a helpful therapy in pathologies such as phantom limb pain, and although the effect has been suggested to be a result of the interaction between pain, vision, touch, and proprioception, the mechanisms are still unknown. Multichannel (124) brain responses were investigated in healthy men (N = 11) and women (N = 14) during the mirror box illusion. Tactile somatosensory evoked potentials were recorded from the right thumb during two control conditions and two illusions: (control 1) no mirror: looking at the physical right thumb during stimulation, (control 2) no mirror: looking at the physical left thumb during stimulation, (illusion 1) mirror: the illusion that both thumbs were stimulated, and (illusion 2) mirror: the illusion that none of the thumbs were stimulated. In men, a significant medial shift in the y coordinate of the N70 dipole in illusion 2 (P = 0.021) was found when compared with illusion 1. No dipole shift was found for women. Additionally, men showed higher prevalence of P180 cingulate cortex activation during illusion 2 when compared with control 1 and 2 (P = 0.002). During illusion 2, the degree of conformity with the statement "The hand in the mirror feels like my other hand" was negatively correlated with the N70 x coordinate for men and positively correlated with the N70 z coordinate for women. In conclusion, short-term cortical plasticity can be induced by a mismatch between visual input and location of tactile stimulation in men. The present study suggests that gender differences exist in the perception of the mirror box illusion.

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

    Science.gov (United States)

    He, Xiao; Wu, Linzhi

    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.

  18. 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.

  19. Apparent size contrasts of retinal images and size constancy as determinants of the moon illusion.

    Science.gov (United States)

    Smith, O W; Smith, P C; Geist, C C; Zimmermann, R R

    1978-06-01

    Kaufman and Rock (1962) and Rock and Kaufman (1962) concluded that the moon illusion is a function of and attributable to apparent distance. They also reported a large framing effect as an exception. Analysis of the effect suggests two components which can account for the illusion independently of apparent distance. These are apparent size contrasts of visual images of discriminable features or objects of the earth with the moon's image and size constancy of the features or objects plus the interactions of the two. Apparent distances to horizons are always a consequence of the necessary conditions for the illusion. They are related to the illusion but are not a determinant of it.

  20. The Viewing-from-Above Bias and the Silhouette Illusion

    Directory of Open Access Journals (Sweden)

    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.

  1. Social misdirection fails to enhance a magic illusion

    OpenAIRE

    Jie eCui; Jorge eOtero-Millan; Macknik, Stephen L.; Mac eKing; Susana eMartinez-Conde

    2011-01-01

    Visual, multisensory and cognitive illusions in magic performances provide new windows into the psychological and neural principles of perception, attention, and cognition. We investigated a magic effect consisting of a coin “vanish” (i.e., the perceptual disappearance of a coin after a simulated toss from hand to hand). Previous research has shown that magicians can use joint attention cues such as their own gaze direction to strengthen the observers’ perception of magic. Here we presented n...

  2. Spatial frequency doubling - Retinal or central. [visual illusion

    Science.gov (United States)

    Richards, W.; Felton, T. B.

    1973-01-01

    When a wide field is sinusoidally modulated both in space and in time, the spatial frequency of the pattern will appear doubled at high rates of modulation. Kelly (1966) proposed that this illusion is due to temporal integration of the nonlinear brightness response of the visual system. The anatomical locus of this temporal integrator is uncertain, and could be subcortical. Results indicate that spatial frequency doubling follows binocular disparity detection and is thus a cortical phenomenon.

  3. Click'n'Roll: No Evidence of Illusion of Control

    OpenAIRE

    Filippin, Antonio; Crosetto, Paolo

    2015-01-01

    Evidence of Illusion of Control – the fact that people believe to have control over pure chance events – is a recurrent finding in experimental psychology. Results in economics find instead little to no support. In this paper we test whether this dissonant result across disciplines is due to the fact that economists have implemented only one form of illusory control. We identify and separately tests in an incentive-compatible design two types of control: a) over the resolution of uncertainty,...

  4. 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.

  5. Stubbornly Persistent Illusion The Essential Scientific Works of Albert Einstein

    CERN Document Server

    Hawking, Stephen

    2009-01-01

    With commentary by the greatest physicist of our time, Stephen Hawking, this anthology has garnered impressive reviews. PW has called it "a gem of a collection" while New Scientist magazine notes the "thrill of reading Einstein's own words." From the writings that revealed the famous Theory of Relativity, to other papers that shook the scientific world of the 20th century, A Stubbornly Persistent Illusion belongs in every science fan's library

  6. 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.

  7. Exploring the subjective experience of the 'rubber hand' illusion

    Directory of Open Access Journals (Sweden)

    Camila eValenzuela Moguillansky

    2013-10-01

    Full Text Available Despite the fact that the rubber hand illusion (RHI is an experimental paradigm that has been widely used in the last 14 years to investigate different aspects of the sense of bodily self, very few studies have sought to investigate the subjective nature of the experience that the RHI evokes. The present study investigates the phenomenology of the RHI through a specific elicitation method. More particularly, this study aim at assessing whether the conditions usually used as control in the RHI have an impact in the sense of body ownership and at determining whether there are different stages in the emergence of the illusion. The results indicate that far from being 'all or nothing,' the illusion induced by the RHI protocol involves nuances in the type of perceptual changes that it creates. These perceptual changes affect not only the participants' perception of the rubber hand but also the perception of their real hand. In addition, perceptual effects may vary greatly between participants and, importantly, they evolve over time.

  8. 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.

  9. Illusion of control: the role of personal involvement.

    Science.gov (United States)

    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.

  10. Optics

    CERN Document Server

    Fincham, W H A

    2013-01-01

    Optics: Ninth Edition Optics: Ninth Edition covers the work necessary for the specialization in such subjects as ophthalmic optics, optical instruments and lens design. The text includes topics such as the propagation and behavior of light; reflection and refraction - their laws and how different media affect them; lenses - thick and thin, cylindrical and subcylindrical; photometry; dispersion and color; interference; and polarization. Also included are topics such as diffraction and holography; the limitation of beams in optical systems and its effects; and lens systems. The book is recommen

  11. The effect of bodily illusions on clinical pain: a systematic review and meta-analysis.

    Science.gov (United States)

    Boesch, Eva; Bellan, Valeria; Moseley, G Lorimer; Stanton, Tasha R

    2016-03-01

    This systematic review and meta-analysis critically examined the evidence for bodily illusions to modulate pain. Six databases were searched; 2 independent reviewers completed study inclusion, risk of bias assessment, and data extraction. Included studies evaluated the effect of a bodily illusion on pain, comparing results with a control group/condition. Of the 2213 studies identified, 20 studies (21 experiments) were included. Risk of bias was high due to selection bias and lack of blinding. Consistent evidence of pain decrease was found for illusions of the existence of a body part (myoelectric/Sauerbruch prosthesis vs cosmetic/no prosthesis; standardized mean differences = -1.84, 95% CI = -2.67 to -1.00) and 4 to 6 weeks of mirror therapy (standardized mean differences = -1.11, 95% CI = -1.66 to -0.56). Bodily resizing illusions had consistent evidence of pain modulation (in the direction hypothesized). Pooled data found no effect on pain for 1 session of mirror therapy or for incongruent movement illusions (except for comparisons with congruent mirrored movements: incongruent movement illusion significantly increased the odds of experiencing pain). Conflicting results were found for virtual walking illusions (both active and inactive control comparisons). Single studies suggest no effect of resizing illusions on pain evoked by noxious stimuli, no effect of embodiment illusions, but a significant pain decrease with synchronous mirrored stroking in nonresponders to traditional mirror therapy. There is limited evidence to suggest that bodily illusions can alter pain, but some illusions, namely mirror therapy, bodily resizing, and use of functional prostheses show therapeutic promise.

  12. Optics

    CERN Document Server

    Fincham, W H A

    2013-01-01

    Optics: Eighth Edition covers the work necessary for the specialization in such subjects as ophthalmic optics, optical instruments and lens design. The text includes topics such as the propagation and behavior of light; reflection and refraction - their laws and how different media affect them; lenses - thick and thin, cylindrical and subcylindrical; photometry; dispersion and color; interference; and polarization. Also included are topics such as diffraction and holography; the limitation of beams in optical systems and its effects; and lens systems. The book is recommended for engineering st

  13. Do Children with Autism Perceive Second-Order Relational Features? The Case of the Thatcher Illusion

    Science.gov (United States)

    Rouse, Helen; Donnelly, Nick; Hadwin, Julie A.; Brown, Tony

    2004-01-01

    Background: This study presents two experiments that investigated whether children with autism were susceptible to the Thatcher illusion. Perception of the Thatcher illusion requires being able to compute second-order configural relations for facial stimuli. Method: In both experiments children with autism were matched for non-verbal and verbal…

  14. 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…

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

    Science.gov (United States)

    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…

  16. The Occurrence Rate of the Fission Illusion Differs Depending on the Complexity of Visual Stimuli

    Directory of Open Access Journals (Sweden)

    Yasuhiro Takeshima

    2011-10-01

    Full Text Available A fission illusion (also named a double—flash illusion is a famous phenomenon of audio-visual interaction, in which a single brief flash is perceived as two flashes when presented simultaneously with two brief beeps (Shames, Kamitani, & Shimojo, 2000; 2002. The fission illusion has been investigated using relatively simple visual stimuli like single circle. Thus the illusion has not been examined by using complex visual stimuli. Markovic & Gvozdenovic (2001 reported that the processing of complex visual stimuli tends to be delayed. Therefore, the complexity of visual stimuli may affect the occurrence rate of the fission illusion, since this illusion is generated in the process that copes with visual and auditory stimuli in a short time. The present study examined the differences in illusory occurrence rates by manipulating the complexity of visual stimuli. We used the patterns proposed by Garner & Clement (1963 to control the complexity. The results indicated that it was more difficult to induce the fission illusion by using complex visual stimuli than it was by using simple stimuli. Thus, the present study suggested that the occurrence rate of the fission illusion differed depending on the perceptual efficiency in the coding process of visual stimuli. This study was supported by Grant-in-Aid for Specifically Promoted Research (No. 19001004.

  17. 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 bod

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

    Science.gov (United States)

    Orgaz, Cristina; Estévez, Ana; Matute, Helena

    2013-01-01

    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 (1) 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 (2), that in addition to gambling-specific problems, pathological gamblers may have a higher-than-normal illusion of control in their daily life.

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

    Directory of Open Access Journals (Sweden)

    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.

  20. Perception of the Auditory-Visual Illusion in Speech Perception by Children with Phonological Disorders

    Science.gov (United States)

    Dodd, Barbara; McIntosh, Beth; Erdener, Dogu; Burnham, Denis

    2008-01-01

    An example of the auditory-visual illusion in speech perception, first described by McGurk and MacDonald, is the perception of [ta] when listeners hear [pa] in synchrony with the lip movements for [ka]. One account of the illusion is that lip-read and heard speech are combined in an articulatory code since people who mispronounce words respond…

  1. Individual Differences in the Multisensory Temporal Binding Window Predict Susceptibility to Audiovisual Illusions

    Science.gov (United States)

    Stevenson, Ryan A.; Zemtsov, Raquel K.; Wallace, Mark T.

    2012-01-01

    Human multisensory systems are known to bind inputs from the different sensory modalities into a unified percept, a process that leads to measurable behavioral benefits. This integrative process can be observed through multisensory illusions, including the McGurk effect and the sound-induced flash illusion, both of which demonstrate the ability of…

  2. Refractive error and monocular viewing strengthen the hollow-face illusion.

    Science.gov (United States)

    Hill, Harold; Palmisano, Stephen; Matthews, Harold

    2012-01-01

    We measured the strength of the hollow-face illusion--the 'flipping distance' at which perception changes between convex and concave--as a function of a lens-induced 3 dioptre refractive error and monocular/binocular viewing. Refractive error and closing one eye both strengthened the illusion to approximately the same extent. The illusion was weakest viewed binocularly without refractive error and strongest viewed monocularly with it. This suggests binocular cues disambiguate the illusion at greater distances than monocular cues, but that both are disrupted by refractive error. We argue that refractive error leaves the ambiguous low-spatial-frequency shading information critical to the illusion largely unaffected while disrupting other, potentially disambiguating, depth/distance cues.

  3. 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...

  4. Lightness of Munker-White illusion and Simultaneous-Contrast illusion: Establishing an ordinal lightness relation among minimum and split-frame presentations

    OpenAIRE

    Li, Ang; Tavantzis, Michael-John; Yazdanbakhsh, Arash

    2009-01-01

    The achromatic Munker-White illusion and the Simultaneous-Contrast illusion have been used extensively in vision studies to understand how the figural configuration of a stimulus can affect the perceived lightness of its components in human perception. Yet, previous modeling and psychophysics studies did not directly compare the illusions’ lightness with controlled parameters of minimum stripes and split-frame presentations, which are useful in testing model predictions and in correlating neu...

  5. Which way is down? Positional distortion in the tilt illusion.

    Science.gov (United States)

    Tomassini, Alessandro; Solomon, Joshua Adam; Morgan, Michael John

    2014-01-01

    Contextual information can have a huge impact on our sensory experience. The tilt illusion is a classic example of contextual influence exerted by an oriented surround on a target's perceived orientation. Traditionally, the tilt illusion has been described as the outcome of inhibition between cortical neurons with adjacent receptive fields and a similar preference for orientation. An alternative explanation is that tilted contexts could produce a re-calibration of the subjective frame of reference. Although the distinction is subtle, only the latter model makes clear predictions for unoriented stimuli. In the present study, we tested one such prediction by asking four naive subjects to estimate three positions (4, 6, and 8 o'clock) on an imaginary clock face within a tilted surround. To indicate their estimates, they used either an unoriented dot or a line segment, with one endpoint at fixation in the middle of the surround. The surround's tilt was randomly chosen from a set of orientations (± 75°, ± 65°, ± 55°, ± 45°, ± 35°, ± 25°, ± 15°, ± 5° with respect to vertical) across trials. Our results showed systematic biases consistent with the tilt illusion in both conditions. Biases were largest when observers attempted to estimate the 4 and 8 o'clock positions, but there was no significant difference between data gathered with the dot and data gathered with the line segment. A control experiment confirmed that biases were better accounted for by a local coordinate shift than to torsional eye movements induced by the tilted context. This finding supports the idea that tilted contexts distort perceived positions as well as perceived orientations and cannot be readily explained by lateral interactions between orientation selective cells in V1.

  6. An ordinal model of the McGurk illusion

    DEFF Research Database (Denmark)

    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...

  7. An Illusion Of Development A nd Technological Decline In Poland

    Directory of Open Access Journals (Sweden)

    Jolanta Sala

    2010-12-01

    Full Text Available Professional IT specialists are still bei ng shocked by inadequacy between the fast IT development in 1970’s and technological decline in 21st century. The stagnation of ICT technologies and their application in social and economic practices in Poland inspired the authors to search for causes and conditions. The authors present the divergent interpretations of New Entrepreneurship st ate from the perspective of micro and macroeconomics. The analyses showed that either “new” or “old” economics is not going to develop without proper economic, institut ional, regulative or social and cultural changes. Unfortunately, the transformation of past two decades is an illusion of development.

  8. Modeling and simulation the computer science of illusion

    CERN Document Server

    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

  9. The Poggendorff illusion effect influenced by top-down control: evidence from an event-related brain potential study.

    Science.gov (United States)

    Liao, Shu; Su, Yanhua; Wu, Xin; Qiu, Jiang

    2011-10-26

    Event-related brain potentials were used to examine the neural correlates of the visual illusion effect in the Poggendorff illusion. In this study, there were three tasks, namely, illusion task 1, illusion task 2 (similar to the classical Poggendorff figures, where the two oblique lines in which individuals were prone to judge to be collinear, were not collinear in fact), and baseline task. Scalp event-related brain potential analysis revealed that (a) both illusion task 1 and illusion task 2 elicited a more negative event-related brain potential deflection (N400-600) than did baseline task, approximately 400 ms after onset of the stimuli, and (b) high-level cognitive control system is, through enhancing the influence of the context on identifying the relationships of the two oblique lines, involved in generating the Poggendorff illusion.

  10. Proprioceptive body illusions modulate the visual perception of reaching distance.

    Directory of Open Access Journals (Sweden)

    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.

  11. Pinhole Viewing Strengthens the Hollow-Face Illusion

    Directory of Open Access Journals (Sweden)

    Trent Koessler

    2015-08-01

    Full Text Available A hollow (concave mask appears convex when viewed from beyond a certain distance even when viewed stereoscopically—this is the hollow-face illusion. At close viewing distances, the same mask is seen as hollow even when disparity information is eliminated by monocular viewing. A potential source of nonpictorial, monocular information that favors a veridical percept at close distances is accommodation in conjunction with focus blur. In this article, we used pinhole viewing to minimize this potential source of information and test whether it affects whether a hollow mask is seen as veridical (concave or illusory (convex. Since monocular viewing also facilitates the illusory (convex percept, it was included in the design both as a comparison and to test whether any effect of accommodation depends on vergence. Pinhole viewing was found favor the illusory percept, and its effect was at least as large as, and added to, that of monocular viewing. A control experiment using tinted glasses that attenuate illumination at least as much as the pinholes did not strengthen the illusion ruling out explanations in terms of reduced luminance. For pinhole viewing, there was no difference between monocular and binocular conditions. The results are interpreted as evidence that focus driven depth information affects perceived three-dimensional shape at close distances even when other sources of depth information are available. The lack of a difference between monocular and binocular pinhole viewing suggests that, by disrupting accommodation, pinholes may also interfere with linked vergence cues to depth.

  12. Changes in visual function during the Coriolis illusion.

    Science.gov (United States)

    Horng, Chi-Ting; Liu, Chung-Cheng; Kuo, Daih-Iluang; Shieh, Po-Chuen; Wu, Yi-Chang; Chen, Jiann-Torng; Tsai, Ming-Ling

    2009-04-01

    The Coriolis illusion produces spatial disorientation and is, therefore, dangerous for pilots. It is not known whether it also affects visual function (visual acuity and stereopsis). There were 18 subjects (15 men and 3 women, mean age 24.7 yr) enrolled in the study. A spatial disorientation simulator was used to produce Coriolis stimulation. The visual acuity of the subjects was evaluated with the Rosenbaum Vision Card before and during Coriolis stimulation. Stereopsis was measured with the Titmus stereo test. Throughout the experiments, eyeball movements were observed on a television monitor. Electrooculography (EOG) and electroencephalography (EEG) were also documented. Before Coriolis stimulation, the visual acuity and stereopsis of all subjects were 20/20 and 40 s of arc, respectively. During the Coriolis illusion, the visual acuity of nine subjects (50%) remained 20/20, whereas the visual acuity of the others (50%) dropped by two lines. The stereopsis of most subjects (77.8%) decreased to 800 arc-seconds or less. Rhythmic nystagmus was observed, while EOG amplitudes were significantly elevated compared with those at baseline (9.41 +/- 0.26 microv2 and 8.45 +/- 0.36 microv2, respectively). EEG activity (frequency) was also greater than at baseline (13.15 +/- 0.84 Hz and 11.94 +/- 1.20 Hz, respectively; P < 0.05). During Coriolis stimulation, the visual acuity of the subjects remained stable, but their stereopsis was reduced. Further study is warranted.

  13. An illusion of control modulates the reluctance to tempt fate

    Directory of Open Access Journals (Sweden)

    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.

  14. Rich Pinch: Perception of Object Movement with Tactile Illusion.

    Science.gov (United States)

    Lee, Jaedong; Kim, Youngsun; Kim, Gerard

    2015-09-01

    Vibrotactile feedback is an effective and economical approach for enriching interactive feedback. However, its effects are mostly limited to providing supplementary alarms or conveying the sense of simple object presence or contact. In this paper, we propose a novel tactile feedback method, called Rich Pinch, based on the "out of body" tactile illusion for selecting and manipulating a virtual object using a two-finger pinch gesture. Rich Pinch uses vibration motors attached only to the two fingertips, but can induce illusory feedback, such as tactile touch/contact and directional movement, as felt from the space between the fingers. We first experimentally verify that the "out of body" illusion technique does in fact exist when applied between the fingertips. Then we compare three different tactile rendering functions to illustrate different resulting perceptual scales and argue to use the tangent-based interpolation in its actual application for a better user performance and experience due to its near-linear perceptual response. Finally, we assess the user experience (focusing on the perception of the object movement of the selected object) of the proposed pinch method by comparing it to the conventional contact-based method. Our results indicate that, with Rich Pinch, users were able to perceive rich dynamic feedback, and clearly preferred it over the conventional method.

  15. Proprioceptive Body Illusions Modulate the Visual Perception of Reaching Distance

    Science.gov (United States)

    Petroni, Agustin; Carbajal, M. Julia; Sigman, Mariano

    2015-01-01

    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. PMID:26110274

  16. Geometric illusions in astronauts during long-duration spaceflight.

    Science.gov (United States)

    Clément, Gilles; Skinner, Anna; Richard, Ghislaine; Lathan, Corinna

    2012-10-24

    In our previous studies, we have shown that the occurrence of geometric illusions was reduced in vestibular patients who presented signs of otolith disorders and when healthy observers were tilted relative to gravity. We hypothesized that the alteration in the gravitational (otolith) input was responsible for this change, presumably because of a connection between vestibular and visual-spatial cognitive functions. In this study, we repeated similar experiments in astronauts during long-duration spaceflight. In agreement with the data of otolithic patients, the inverted-T geometric illusion was less present in the astronauts in 0 g than in 1g. In addition, the vertical length of drawings made by astronauts in orbit was shorter than that on the ground. This result is also comparable with the otolithic patients who perceived the vertical length of line drawings to be smaller than healthy individuals. We conclude that the impairment in the processing of gravitational input in long-duration astronauts affects their mental representation of the vertical dimension similar to the otolithic patients. The astronauts, however, recover to baseline levels within 1 week after returning to Earth.

  17. Reduced susceptibility to the sound-induced flash fusion illusion in schizophrenia.

    Science.gov (United States)

    Vanes, Lucy D; White, Thomas P; Wigton, Rebekah L; Joyce, Dan; Collier, Tracy; Shergill, Sukhi S

    2016-11-30

    Schizophrenia is characterised by the presence of abnormal complex sensory perceptual experiences. Such experiences could arise as a consequence of dysfunctional multisensory integration. We used the sound-induced flash illusion paradigm, which probes audiovisual integration using elementary visual and auditory cues, in a sample of individuals with schizophrenia (n=40) and matched controls (n=22). Signal detection theory analyses were performed to characterise patients' and controls' sensitivity in distinguishing 1 and 2 flashes under varying auditory conditions. Both groups experienced significant fission illusions (whereby one visual flash, accompanied by two auditory beeps, is misperceived as two flashes) and fusion illusions (whereby two flashes, accompanied by one beep, are perceived as one flash). Patients showed significantly lower fusion illusion rates compared to HC, while the fission illusion occurred similarly frequently in both groups. However, using an SDT approach, we compared illusion conditions with unimodal visual conditions, and found that illusory visual perception was overall more strongly influenced by auditory input in HC compared to patients for both illusions. This suggests that multisensory integration may be impaired on a low perceptual level in SZ.

  18. Preliminary study to investigate the Delboeuf illusion in ring-tailed lemurs (Lemur catta: Methodological Challenges.

    Directory of Open Access Journals (Sweden)

    Maria Santacà

    2017-08-01

    Full Text Available Visual illusions are commonly used in animal cognition studies to compare visual perception among vertebrates. To date, researchers have focused their attention mainly on birds and mammals, especially apes and monkeys, but no study has investigated sensitivity to visual illusions in prosimians. Here we investigated whether lemurs (Lemur catta perceive the Delboeuf illusion, a well-known illusion that occurs when subjects misperceive the relative size of an item because of its surrounding context. In particular, we adopted the spontaneous preference paradigm used in chimpanzees and observed lemurs’ ability to select the larger amount of food. In control trials, we presented two different amounts of food on two identical plates. In test trials, we presented equal food portion sizes on two plates differing in size: If lemurs were sensitive to the illusion, they were expected to select the food portion presented on the smaller plate. In control trials, they exhibited poor performance compared to other mammals previously observed, being able to discriminate between the two quantities only in the presence of a 0.47 ratio. This result prevented us from drawing any conclusion regarding the subjects’ susceptibility to the Delboeuf illusion. In test trials with the illusory pattern, however, the subjects’ choices did not differ from chance. Our data suggest that the present paradigm is not optimal for testing the perception of the Delboeuf illusion in lemurs and highlight the importance of using different methodological approaches to assess the perceptual mechanisms underlying size discrimination among vertebrates.

  19. The visual phantom illusion: A perceptual product of surface completion depending on brightness and contrast.

    Science.gov (United States)

    Kitaoka, Akiyoshi; Gyoba, Jiro; Sakurai, Kenzo

    2006-01-01

    The visual phantom illusion was first discovered by Rosenbach in 1902 and named 'moving phantoms' by Tynan and Sekuler in 1975 because of its strong dependence on motion. It was later revealed that phantoms can be generated by flickering the grating (flickering phantoms) or by low-luminance stationary gratings under dark adaptation (stationary phantoms). Although phantoms are much more visible at scotopic or mesopic adaptation levels (scotopic phantoms) than at photopic levels, we proposed a new phantom illusion which is fully visible in photopic vision (photopic phantoms). In 2001, we revealed that the visual phantom illusion is a higher-order perceptual construct or a Gestalt, which depends on the mechanism of perceptual transparency. Perceptual transparency is known as a perceptual product based upon brightness and contrast. We furthermore manifested the shared mechanisms between visual phantoms and neon color spreading or between visual phantoms and the Petter effect. In our recent study, the visual phantom illusion can also be seen with a stimulus of contrast-modulated gratings. We assume that this effect also depends on perceptual transparency induced by contrast modulation. Moreover, we found that the Craik-O'Brien-Cornsweet effect and other brightness illusions can generate the visual phantom illusion. In any case, we explain the visual phantom illusion in terms of surface completion, which is given by perceptual transparency.

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

    Science.gov (United States)

    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.

  1. 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

  2. Reducing the illusion of control when an action is followed by an undesired outcome.

    Science.gov (United States)

    Matute, Helena; Blanco, Fernando

    2014-08-01

    The illusion of control is the belief that our behavior produces an effect that is actually independent from it. This illusion is often at the core of superstitious and pseudoscientific thinking. Although recent research has proposed several evidence-based strategies that can be used to reduce the illusion, the majority of these experiments have involved positive illusions-that is, those in which the potential outcomes are desired (e.g., recovery from illness or earning points). By contrast, many real-life superstitions and pseudosciences are tied to negative illusions-that is, those in which the potential consequences are undesired. Examples are walking under a ladder, breaking a mirror, or sitting in row 13, all of which are supposed to generate bad luck. Thus, the question is whether the available evidence on how to reduce positive illusions would also apply to situations in which the outcomes are undesired. We conducted an experiment in which participants were exposed to undesired outcomes that occurred independently of their behavior. One strategy that has been shown to reduce positive illusions consists of warning people that the outcomes might have alternative causes, other than the participants' actions, and telling them that the best they can do to find out whether an alternative cause is at work is to act on only about 50% of the trials. When we gave our participants this information in an experiment in which the outcomes were undesired, their illusion was enhanced rather than reduced, contrary to what happens when the outcome is desired. This suggests that the strategies that reduce positive illusions may work in just the opposite way when the outcome is undesired.

  3. Effectiveness of transcranial direct current stimulation and visual illusion on neuropathic pain in spinal cord injury.

    Science.gov (United States)

    Soler, Maria Dolors; Kumru, Hatice; Pelayo, Raul; Vidal, Joan; Tormos, Josep Maria; Fregni, Felipe; Navarro, Xavier; Pascual-Leone, Alvaro

    2010-09-01

    The aim of this study was to evaluate the analgesic effect of transcranial direct current stimulation of the motor cortex and techniques of visual illusion, applied isolated or combined, in patients with neuropathic pain following spinal cord injury. In a sham controlled, double-blind, parallel group design, 39 patients were randomized into four groups receiving transcranial direct current stimulation with walking visual illusion or with control illusion and sham stimulation with visual illusion or with control illusion. For transcranial direct current stimulation, the anode was placed over the primary motor cortex. Each patient received ten treatment sessions during two consecutive weeks. Clinical assessment was performed before, after the last day of treatment, after 2 and 4 weeks follow-up and after 12 weeks. Clinical assessment included overall pain intensity perception, Neuropathic Pain Symptom Inventory and Brief Pain Inventory. The combination of transcranial direct current stimulation and visual illusion reduced the intensity of neuropathic pain significantly more than any of the single interventions. Patients receiving transcranial direct current stimulation and visual illusion experienced a significant improvement in all pain subtypes, while patients in the transcranial direct current stimulation group showed improvement in continuous and paroxysmal pain, and those in the visual illusion group improved only in continuous pain and dysaesthesias. At 12 weeks after treatment, the combined treatment group still presented significant improvement on the overall pain intensity perception, whereas no improvements were reported in the other three groups. Our results demonstrate that transcranial direct current stimulation and visual illusion can be effective in the management of neuropathic pain following spinal cord injury, with minimal side effects and with good tolerability.

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

    Science.gov (United States)

    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.

  5. Transformation Optics, Generalized Cloaking and Superlenses

    CERN Document Server

    Nicolet, Andre; Geuzaine, Christophe; 10.1109/TMAG.2010.2043073

    2010-01-01

    In this paper, transformation optics is presented together with a generalization of invisibility cloaking: instead of an empty region of space, an inhomogeneous structure is transformed via Pendry's map in order to give, to any object hidden in the central hole of the cloak, a completely arbitrary appearance. Other illusion devices based on superlenses considered from the point of view of transformation optics are also discussed.

  6. Getting real about Semantic Illusions : Rethinking the functional role of the P600 in language comprehension

    NARCIS (Netherlands)

    Brouwer, Harm; Fitz, Hartmut; Hoeks, John

    2012-01-01

    In traditional theories of language comprehension, syntactic and semantic processing are inextricably linked. This assumption has been challenged by the 'Semantic: Illusion Effect' found in studies using Event Related brain Potentials. Semantically anomalous sentences did not produce the expected in

  7. Three-dimensional broadband acoustic illusion cloak for sound-hard boundaries of curved geometry

    Science.gov (United States)

    Kan, Weiwei; Liang, Bin; Li, Ruiqi; Jiang, Xue; Zou, Xin-Ye; Yin, Lei-Lei; Cheng, Jianchun

    2016-11-01

    Acoustic illusion cloaks that create illusion effects by changing the scattered wave have many potential applications in a variety of scenarios. However, the experimental realization of generating three-dimensional (3D) acoustic illusions under detection of broadband signals still remains challenging despite the paramount importance for practical applications. Here we report the design and experimental demonstration of a 3D broadband cloak that can effectively manipulate the scattered field to generate the desired illusion effect near curved boundaries. The designed cloak simply comprises positive-index anisotropic materials, with parameters completely independent of either the cloaked object or the boundary. With the ability of manipulating the scattered field in 3D space and flexibility of applying to arbitrary geometries, our method may take a major step toward the real world application of acoustic cloaks and offer the possibilities of building advanced acoustic devices with versatile functionalities.

  8. Effectiveness of transcranial direct current stimulation and visual illusion on neuropathic pain in spinal cord injury

    National Research Council Canada - National Science Library

    Soler, Maria Dolors; Kumru, Hatice; Pelayo, Raul; Vidal, Joan; Tormos, Josep Maria; Fregni, Felipe; Navarro, Xavier; Pascual-Leone, Alvaro

    2010-01-01

    ... with neuropathic pain following spinal cord injury. In a sham controlled, double-blind, parallel group design, 39 patients were randomized into four groups receiving transcranial direct current stimulation with walking visual illusion or with control...

  9. 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...... cortex. Mismatch Negativity (MMN) is a component in the auditory Event-Related Potential (ERP) that is elicited by a change in the auditory percept. It has been shown that the McGurk illusion can induce a MMN. We conducted an experiment in which the MMN could be elicited by the McGurk illusion induced...... 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...

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

    Science.gov (United States)

    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.

  11. 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)

  12. 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)

  13. Implementation and Assessment of an Intervention to Debias Adolescents against Causal Illusions: e71303

    National Research Council Canada - National Science Library

    Itxaso Barberia; Fernando Blanco; Carmelo P Cubillas; Helena Matute

    2013-01-01

      Researchers have warned that causal illusions are at the root of many superstitious beliefs and fuel many people's faith in pseudoscience, thus generating significant suffering in modern society...

  14. San Lorenzo and the Poggendorff Illusion in Ravenna

    Directory of Open Access Journals (Sweden)

    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.

  15. San Lorenzo and the Poggendorff illusion in Ravenna.

    Science.gov (United States)

    Daneyko, Olga; Stucchi, Natale; Zavagno, Daniele

    2011-01-01

    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.

  16. DEMAND ILLUSION AS A WAY TO REDUCE COSTS

    Directory of Open Access Journals (Sweden)

    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.

  17. Visual illusion of tool use recalibrates tactile perception.

    Science.gov (United States)

    Miller, Luke E; Longo, Matthew R; Saygin, Ayse P

    2017-02-11

    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.

  18. Creating illusions of past encounter through brief exposure.

    Science.gov (United States)

    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.

  19. Mind Reading in Stage Magic: The “Second Sight” Illusion, Media, and Mediums

    OpenAIRE

    Katharina Rein

    2015-01-01

    This article analyzes the late-nineteenth-century stage illusion “The Second Sight,” which seemingly demonstrates the performers’ telepathic abilities. The illusion is on the one hand regarded as an expression of contemporary trends in cultural imagination as it seizes upon notions implied by spiritualism as well as utopian and dystopian ideas associated with technical media. On the other hand, the spread of binary code in communication can be traced along with the development of the "Second ...

  20. Aristotle’s Illusion in Parkinson’s Disease: Evidence for Normal Interdigit Tactile Perception

    Science.gov (United States)

    Fiorio, Mirta; Marotta, Angela; Ottaviani, Sarah; Pozzer, Lara; Tinazzi, Michele

    2014-01-01

    Sensory alterations, a common feature of such movement disorders as Parkinson’s disease (PD) and dystonia, could emerge as epiphenomena of basal ganglia dysfunction. Recently, we found a selective reduction of tactile perception (Aristotle’s illusion, the illusory doubling sensation of one object when touched with crossed fingers) in the affected hand of patients with focal hand dystonia. This suggests that reduced tactile illusion might be a specific feature of this type of dystonia and could be due to abnormal somatosensory cortical activation. The aim of the current study was to investigate whether Aristotle’s illusion is reduced in the affected hand of patients with PD. We tested 15 PD patients, in whom motor symptoms were mainly localised to one side of the body, and 15 healthy controls. Three pairs of fingers were tested in crossed (evoking the illusion) or parallel position (not evoking the illusion). A sphere was placed in the contact point between the two fingers and the blindfolded participants had to say whether they felt one or two stimuli. Stimuli were applied on the affected and less or unaffected side of the PD patients. We found no difference in illusory perception between the PD patients and the controls, nor between the more affected and less/unaffected side, suggesting that Aristotle’s illusion is preserved in PD. The retained tactile illusion in PD and its reduction in focal hand dystonia suggest that the basal ganglia, which are dysfunctional in both PD and dystonia, may not be causally involved in this function. Instead, the level of activation between digits in the somatosensory cortex may be more directly involved. Finally, the similar percentage of illusion in the more affected and less or unaffected body sides indicates that the illusory perception is not influenced by the presence or amount of motor symptoms. PMID:24523929

  1. Aristotle's illusion in Parkinson's disease: evidence for normal interdigit tactile perception.

    Science.gov (United States)

    Fiorio, Mirta; Marotta, Angela; Ottaviani, Sarah; Pozzer, Lara; Tinazzi, Michele

    2014-01-01

    Sensory alterations, a common feature of such movement disorders as Parkinson's disease (PD) and dystonia, could emerge as epiphenomena of basal ganglia dysfunction. Recently, we found a selective reduction of tactile perception (Aristotle's illusion, the illusory doubling sensation of one object when touched with crossed fingers) in the affected hand of patients with focal hand dystonia. This suggests that reduced tactile illusion might be a specific feature of this type of dystonia and could be due to abnormal somatosensory cortical activation. The aim of the current study was to investigate whether Aristotle's illusion is reduced in the affected hand of patients with PD. We tested 15 PD patients, in whom motor symptoms were mainly localised to one side of the body, and 15 healthy controls. Three pairs of fingers were tested in crossed (evoking the illusion) or parallel position (not evoking the illusion). A sphere was placed in the contact point between the two fingers and the blindfolded participants had to say whether they felt one or two stimuli. Stimuli were applied on the affected and less or unaffected side of the PD patients. We found no difference in illusory perception between the PD patients and the controls, nor between the more affected and less/unaffected side, suggesting that Aristotle's illusion is preserved in PD. The retained tactile illusion in PD and its reduction in focal hand dystonia suggest that the basal ganglia, which are dysfunctional in both PD and dystonia, may not be causally involved in this function. Instead, the level of activation between digits in the somatosensory cortex may be more directly involved. Finally, the similar percentage of illusion in the more affected and less or unaffected body sides indicates that the illusory perception is not influenced by the presence or amount of motor symptoms.

  2. Alpha-band oscillations reflect altered multisensory processing of the McGurk illusion in schizophrenia

    Directory of Open Access Journals (Sweden)

    Yadira eRoa Romero

    2016-02-01

    Full Text Available The formation of coherent multisensory percepts requires integration of stimuli across the multiple senses. Patients with schizophrenia (ScZ often experience a loss of coherent perception and hence, they might also show dysfunctional multisensory processing. In this high-density electroencephalography study we investigated the neural signatures of the McGurk illusion, as a phenomenon of speech-specific multisensory processing. In the McGurk illusion lip movements are paired with incongruent auditory syllables, which can induce a fused percept. In ScZ patients and healthy controls we compared neural oscillations and event-related potentials (ERPs to congruent audiovisual speech stimuli and McGurk illusion trials, where a visual /ga/ and an auditory /pa/ was often perceived as /ka/. There were no significant group differences in illusion rates. However, we found larger short latency ERPs to McGurk illusion compared with congruent trials in controls, whereas they were reduced in ScZ patients, indicating an early audiovisual processing deficit. Moreover, we observed stronger suppression of medio-central alpha-band power (8-10 Hz, 550-700 ms in response to McGurk illusion compared with control trials in the control group. The reversed pattern was found in SCZ patients. Within groups, alpha-band suppression was negatively correlated with the McGurk illusion rate in ScZ patients, while the correlation tended to be positive in controls. The topography of alpha-band effects suggests an involvement of auditory and/or frontal structures. Our study suggests that early ERPs and later alpha-band oscillations reflect abnormal multisensory processing of the McGurk illusion in schizophrenia.

  3. The impact of visual illusions on perception, action planning, and motor performance.

    Science.gov (United States)

    Wood, Greg; Vine, Samuel J; Wilson, Mark R

    2013-07-01

    The present study extended recent research revealing that illusions can influence performance in golf putting (Witt, Linkenauger, & Proffitt Psychological Science, 23, 397-399, 2012), by exploring the potential mediating roles of attention and action planning. Glover and Dixon's (Journal of Experimental Psychology. Human Perception and Performance, 27, 560-572, 2001) planning-control model suggests that both perceptual and movement-planning processes are prone to illusion-based bias. We therefore predicted that both the perception of target size and a measure of attentional control related to movement planning in golf putting (the quiet eye) would be influenced by the illusion. Moreover, as performance could not be corrected using online control (once the ball was struck), we predicted that these biases would also influence performance. We therefore proposed a three-stage process by which illusory context biases perceptual processes, which in turn bias subsequent attentional control related to movement planning, which in turn biases motor performance. Forty novice golfers completed an Ebbinghaus illusion putting task that was designed to manipulate their perceptions of target size, while quiet eye duration and performance (mean radial error) were measured. The results indicated that the illusion was effective in facilitating differences in perceived target size, with perceptually bigger holes promoting longer quiet eye durations and more accurate putting. Follow-up mediation analyses revealed that illusion-based differences in size perception partially mediated illusion-based differences in both quiet eye duration and performance. Moreover, the relationship between illusion-based differences in quiet eye duration and performance was also significant. Future research should further test this three-stage process of bias in other far-aiming tasks in which online control cannot be used.

  4. Fiscal illusion and the shadow economy: Two sides of the same coin?

    OpenAIRE

    Buehn, Andreas; DELL'ANNO, Roberto; Schneider, Friedrich

    2013-01-01

    This paper presents an empirical analysis of the relationship between fiscal illusion and the shadow economy for 104 countries over the period 1989–2009. We argue that both unobservable phenomena are closely linked to each other, as the creation of a fiscal illusion may be helpful if governments want to control shadow economic activities. Using a MIMIC model with two latent variables we confirm previous findings on the driving forces of the shadow economy and identify the main determinants an...

  5. A Film Buff’s Paradox: The Evolution of Illusion vs. Reality

    Directory of Open Access Journals (Sweden)

    Armand Amini

    2015-07-01

    Full Text Available In this cinematic realm, the concept of illusion vs. reality is a theme that has attracted artistic exploration, and has proven to be an enduring and significant storytelling framework in the realm of contemporary cinema. This theme of illusion vs. reality is witnessed in films from as far back as George Méliès 1902 A Trip to the Moon, to the 1964 version of Mary Poppins, to contemporary offerings such as The Matrix in 1999.

  6. Audition influences color processing in the sound-induced visual flash illusion

    OpenAIRE

    Mishra, Jyoti; Martinez, Antigona; Hillyard, Steven A.

    2013-01-01

    Multisensory interactions can lead to illusory percepts, as exemplified by the sound-induced extra flash illusion (SIFI: Shams et al., 2000, 2002). In this illusion, an audio-visual stimulus sequence consisting of two pulsed sounds and a light flash presented within a 100 ms time window generates the visual percept of two flashes. Here, we used colored visual stimuli to investigate whether concurrent auditory stimuli can affect the perceived features of the illusory flash. Zero, one or two pu...

  7. Individual Differences in the Multisensory Temporal Binding Window Predict Susceptibility to Audiovisual Illusions

    OpenAIRE

    Stevenson, Ryan A.; Raquel K Zemtsov; Wallace, Mark T.

    2012-01-01

    Human multisensory systems are known to bind inputs from the different sensory modalities into a unified percept, a process that leads to measurable behavioral benefits. This integrative process can be observed through multisensory illusions, including the McGurk effect and the sound-induced flash illusion, both of which demonstrate the ability of one sensory modality to modulate perception in a second modality. Such multisensory integration is highly dependent upon the temporal relationship ...

  8. Aristotle's illusion in Parkinson's disease: evidence for normal interdigit tactile perception.

    Directory of Open Access Journals (Sweden)

    Mirta Fiorio

    Full Text Available Sensory alterations, a common feature of such movement disorders as Parkinson's disease (PD and dystonia, could emerge as epiphenomena of basal ganglia dysfunction. Recently, we found a selective reduction of tactile perception (Aristotle's illusion, the illusory doubling sensation of one object when touched with crossed fingers in the affected hand of patients with focal hand dystonia. This suggests that reduced tactile illusion might be a specific feature of this type of dystonia and could be due to abnormal somatosensory cortical activation. The aim of the current study was to investigate whether Aristotle's illusion is reduced in the affected hand of patients with PD. We tested 15 PD patients, in whom motor symptoms were mainly localised to one side of the body, and 15 healthy controls. Three pairs of fingers were tested in crossed (evoking the illusion or parallel position (not evoking the illusion. A sphere was placed in the contact point between the two fingers and the blindfolded participants had to say whether they felt one or two stimuli. Stimuli were applied on the affected and less or unaffected side of the PD patients. We found no difference in illusory perception between the PD patients and the controls, nor between the more affected and less/unaffected side, suggesting that Aristotle's illusion is preserved in PD. The retained tactile illusion in PD and its reduction in focal hand dystonia suggest that the basal ganglia, which are dysfunctional in both PD and dystonia, may not be causally involved in this function. Instead, the level of activation between digits in the somatosensory cortex may be more directly involved. Finally, the similar percentage of illusion in the more affected and less or unaffected body sides indicates that the illusory perception is not influenced by the presence or amount of motor symptoms.

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

    Directory of Open Access Journals (Sweden)

    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”.

  10. Seeing size and feeling weight: the size-weight illusion in natural and virtual reality.

    Science.gov (United States)

    Heineken, Edgar; Schulte, Frank P

    2007-02-01

    We experimentally tested the degree that the size-weight illusion depends on perceptual conditions allowing the observer to assume that both the visual and the kinesthetic stimuli of a weight seen and lifted emanate from the same object. We expected that the degree of the illusion depended on the "realism" provided by different kinds of virtual reality (VR) used when the weights are seen in virtual reality and at the same time lifted in natural reality. Welch and Warren (1980) reported that an intermodal influence can be expected only if perceptual information of different modalities is compellingly related to only one object. Objects of different sizes and weights were presented to 50 participants in natural reality or in four virtual realities: two immersive head-mounted display VRs (with or without head tracking) and two nonimmersive desktop VRs (with or without screening from input of the natural environment using a visor). The objects' heaviness was scaled using the magnitude estimation method. Data show that the degree of the illusion is largest in immersive and lowest in nonimmersive virtual realities. The higher the degree of the illusion is, the more compelling the situation is perceived and the more the observed data are in correspondence with the data predicted for the illusion in natural reality. This shows that the kind of mediating technology used strongly influences the presence experienced. The size-weight illusion's sensitivity to conditions that affect the sense of presence makes it a promising objective presence measure.

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

    Directory of Open Access Journals (Sweden)

    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.

  12. Sad mood increases pain sensitivity upon thermal grill illusion stimulation: implications for central pain processing.

    Science.gov (United States)

    Boettger, Michael Karl; Schwier, Christiane; Bär, Karl-Jürgen

    2011-01-01

    In different fields of neuroscience research, illusions have successfully been used to unravel underlying mechanisms of stimulus processing. One such illusion existing for the field of pain research is the so-called thermal grill illusion. Here, painful sensations are elicited by interlacing warm and cold bars, with stimulus intensities (temperatures) of these bars being below the respective heat pain or cold pain thresholds. To date, the underlying mechanisms of this phenomenon are not completely understood. There is some agreement, however, that the sensation evoked by this stimulation is generated by central nervous interactions. Therefore, we followed two approaches in this study: firstly, we aimed at developing and validating a water-driven device which might be used in fMRI scanners in future studies - subject to minor adaptations. Secondly, we aimed to interfere with this illusion by induction of a sad mood state, a procedure which is suggested to influence central nervous structures that are also involved in pain processing. The newly developed device induced thermal grill sensations similar to those reported in the literature. Induction of sad, but not neutral mood states, resulted in higher pain and unpleasantness ratings of the painful illusion. These findings might be of importance for the understanding of pain processing in healthy volunteers, but putatively even more so in patients with major depressive disorder. Moreover, our results might indicate that central nervous structures involved in the affective domain or cognitive domain of pain processing might be involved in the perception of the illusion.

  13. Rotating Snakes Illusion-Quantitative Analysis Reveals a Region in Luminance Space With Opposite Illusory Rotation.

    Science.gov (United States)

    Atala-Gérard, Lea; Bach, Michael

    2017-01-01

    The Rotating Snakes Illusion employs patterns with repetitive asymmetric luminance steps forming a "snake wheel." In the underlying luminance sequence {black, dark grey, white, light grey}, coded as {0, g1, 100, g2}, we varied g1 and g2 and measured illusion strength via nulling: Saccades were performed next to a "snake wheel" that rotated physically; observers adjusted rotation until a stationary percept obtained. Observers performed the perceptual nulling of the seeming rotation reliably. Typical settings for (g1, g2), measured from images by Kitaoka, are around (20%, 60%). Indeed, we found a marked illusion in the region (g1≈{0%-25%}, g2≈{20%-75%}) with a rotation speed of ≈1°/s. Surprisingly, we detected a second "island" around (70%, 95%) with opposite direction of the illusory rotation and weaker illusion. Our quantitative measurements of illusion strength confirmed the optimal luminance choices of the standard snake wheel and, unexpectedly, revealed an opposite rotation illusion.

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

    Science.gov (United States)

    Zeman, Astrid; Obst, Oliver; Brooks, Kevin R; Rich, Anina N

    2013-01-01

    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.

  15. Do rhesus monkeys (Macaca mulatta) perceive the Zöllner illusion?

    Science.gov (United States)

    Agrillo, Christian; Parrish, Audrey E; Beran, Michael J

    2014-08-01

    A long-standing debate surrounds the issue of whether human and nonhuman animals share the same perceptual mechanisms. In humans, the Zöllner illusion occurs when two parallel lines appear to be convergent when oblique crosshatching lines are superimposed. Although one baboon study suggests that they too might perceive this illusion, the results of that study were unclear, whereas two recent studies suggest that birds see this illusion in the opposite direction from humans. It is currently unclear whether these mixed results are an artifact of the experimental design or reflect a peculiarity of birds' visual system or, instead, a wider phenomenon shared among nonhuman mammals. Here, we trained 6 monkeys to select the narrower of two gaps at the end of two convergent lines. Three different conditions were set up: control (no crosshatches), perpendicular (crosshatches not inducing the illusion), and Zöllner (crosshatches inducing the illusion in humans). During training, the degrees of convergence between the two lines ranged from 15° to 12°. Monkeys that reached the training criterion were tested with more difficult discriminations (11°-1°), including probe trials with parallel lines (0°). The results showed that monkeys perceived the Zöllner illusion in the same direction as humans. Comparison of these data with the data from bird studies points toward the existence of different orientation-tuned mechanisms between primate and nonprimate species.

  16. An auditory illusion reveals the role of streaming in the temporal misallocation of perceptual objects.

    Science.gov (United States)

    Mehta, Anahita H; Jacoby, Nori; Yasin, Ifat; Oxenham, Andrew J; Shamma, Shihab A

    2017-02-19

    This study investigates the neural correlates and processes underlying the ambiguous percept produced by a stimulus similar to Deutsch's 'octave illusion', in which each ear is presented with a sequence of alternating pure tones of low and high frequencies. The same sequence is presented to each ear, but in opposite phase, such that the left and right ears receive a high-low-high … and a low-high-low … pattern, respectively. Listeners generally report hearing the illusion of an alternating pattern of low and high tones, with all the low tones lateralized to one side and all the high tones lateralized to the other side. The current explanation of the illusion is that it reflects an illusory feature conjunction of pitch and perceived location. Using psychophysics and electroencephalogram measures, we test this and an alternative hypothesis involving synchronous and sequential stream segregation, and investigate potential neural correlates of the illusion. We find that the illusion of alternating tones arises from the synchronous tone pairs across ears rather than sequential tones in one ear, suggesting that the illusion involves a misattribution of time across perceptual streams, rather than a misattribution of location within a stream. The results provide new insights into the mechanisms of binaural streaming and synchronous sound segregation.This article is part of the themed issue 'Auditory and visual scene analysis'.

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

    Directory of Open Access Journals (Sweden)

    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.

  18. 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

  19. The effect of age on the haptic horizontal-vertical curvature illusion with raised-line shapes.

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    Ballesteros, Soledad; Mayas, Julia; Reales, José Manuel; Heller, Morton

    2012-01-01

    In the present study, we investigated the effect of age in the haptic horizontal-vertical curvature illusion from adolescence to old age. Blindfolded participants explored raised-line convex curves with one finger and two fingers (Experiment 1). They judged the size of the curves (horizontal/vertical), using two sliding rulers. The results suggest that young and older haptic explorers overestimated the vertical. Adolescents did not show the haptic illusion. In Experiment 2, adolescents performed the task visually showing a stronger horizontal-vertical illusion. The findings suggest that the illusion develops later in touch than in vision. The theoretical implications of the results are discussed.

  20. 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

    2016-01-01

    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 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. PMID:27654174

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

    Science.gov (United States)

    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.

  2. Visual illusions, delayed grasping, and memory: no shift from dorsal to ventral control.

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    Franz, V H; Hesse, C; Kollath, S

    2009-05-01

    We tested whether a delay between stimulus presentation and grasping leads to a shift from dorsal to ventral control of the movement, as suggested by the perception-action theory of Milner and Goodale (Milner, A.D., & Goodale, M.A. (1995). The visual brain in action. Oxford: Oxford University Press.). In this theory the dorsal cortical stream has a short memory, such that after a few seconds the dorsal information is decayed and the action is guided by the ventral stream. Accordingly, grasping should become responsive to certain visual illusions after a delay (because only the ventral stream is assumed to be deceived by these illusions). We used the Müller-Lyer illusion, the typical illusion in this area of research, and replicated the increase of the motor illusion after a delay. However, we found that this increase is not due to memory demands but to the availability of visual feedback during movement execution which leads to online corrections of the movement. Because such online corrections are to be expected if the movement is guided by one single representation of object size, we conclude that there is no evidence for a shift from dorsal to ventral control in delayed grasping of the Müller-Lyer illusion. We also performed the first empirical test of a critique Goodale (Goodale, M.A. (2006, October 27). Visual duplicity: Action without perception in the human visual system. The XIV. Kanizsa lecture, Triest, Italy.) raised against studies finding illusion effects in grasping: Goodale argued that these studies used methods that lead to unnatural grasping which is guided by the ventral stream. Therefore, these studies might never have measured the dorsal stream, but always the ventral stream. We found clear evidence against this conjecture.

  3. 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.

  4. 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.

  5. The Two-Wrongs model explains perception-action dissociations for illusions driven by distortions of the egocentric reference frame

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    Paul eDassonville

    2015-03-01

    Full Text Available Several studies have demonstrated a dissociation of the effects of illusion on perception and action, with perception generally reported to be susceptible to illusions, while actions are seemingly immune. These findings have been interpreted to support Milner and Goodale's Two Visual Systems model, which proposes the existence of separate visual processing streams for perception and action. However, an alternative interpretation suggests that this type of behavioral dissociation will occur for any illusion that is caused by a distortion of the observer's egocentric reference frame, without requiring the existence of separate perception and action systems that are differently affected by the illusion. In this scenario, movements aimed at illusory targets will be accurate if they are guided within the same distorted reference frame used for target encoding, since the error of motor guidance will cancel with the error of encoding (hence, for actions, two wrongs do make a right. We further test this Two-Wrongs model by examining two illusions for which the hypothesis makes very different predictions: the rod-and-frame illusion (which affects perception but not actions and the simultaneous-tilt illusion (which affects perception and actions equally. We demonstrate that the rod-and-frame illusion is caused by a distortion of the observer's egocentric reference frame suitable for the cancellation of errors predicted by the Two-Wrongs model. In contrast, the simultaneous-tilt illusion is caused by local interactions between stimulus elements within an undistorted reference frame, precluding the cancellation of errors associated with the Two-Wrongs model such that the illusion is reflected in both perception and actions. These results provide evidence for a class of illusions that lead to dissociations of perception and action through distortions of the observer's spatial reference frame, rather than through the actions of functionally separate visual

  6. Belief in the unstructured interview: The persistence of an illusion

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    Jason Dana

    2013-09-01

    Full Text Available Unstructured interviews are a ubiquitous tool for making screening decisions despite a vast literature suggesting that they have little validity. We sought to establish reasons why people might persist in the illusion that unstructured interviews are valid and what features about them actually lead to poor predictive accuracy. In three studies, we investigated the propensity for ``sensemaking'' - the ability for interviewers to make sense of virtually anything the interviewee says---and ``dilution''---the tendency for available but non-diagnostic information to weaken the predictive value of quality information. In Study 1, participants predicted two fellow students' semester GPAs from valid background information like prior GPA and, for one of them, an unstructured interview. In one condition, the interview was essentially nonsense in that the interviewee was actually answering questions using a random response system. Consistent with sensemaking, participants formed interview impressions just as confidently after getting random responses as they did after real responses. Consistent with dilution, interviews actually led participants to make worse predictions. Study 2 showed that watching a random interview, rather than personally conducting it, did little to mitigate sensemaking. Study 3 showed that participants believe unstructured interviews will help accuracy, so much so that they would rather have random interviews than no interview. People form confident impressions even interviews are defined to be invalid, like our random interview, and these impressions can interfere with the use of valid information. Our simple recommendation for those making screening decisions is not to use them.

  7. The Thatcher illusion: rotating the viewer instead of the picture.

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    Lobmaier, Janek S; Mast, Fred W

    2007-01-01

    Faces are difficult to recognise when presented upside down. This effect of face inversion was effectively demonstrated with the 'Thatcher illusion' by Thompson (1980 Perception 9 483-484). It has been tacitly assumed that this effect is due to inversion relative to retinal coordinates. Here we tested whether it is due to egocentric (i.e. retinal) inversion or whether the orientation of the body with respect to gravity also influences the face-inversion effect. A 3-D human turntable was used to test subjects in 5 different body-tilt (roll) orientations: 0 degree, 45 degrees, 90 degrees, 135 degrees, and 180 degrees. The stimuli consisted of 4 'normal' and 4 'thatcherised' faces and were presented in 8 different orientations in the picture plane. The subjects had to decide in a yes-no task whether the faces were 'normal' or 'thatcherised'. Analysis of the d' values revealed a significant effect of stimulus orientation and body tilt. The significant effect of body tilt was due to a drop in d' values in the 135 degrees orientation. This result is compared to findings of studies on the subjective visual vertical, where larger errors occurred in body-tilt orientations between 90 degrees and 180 degrees. The present findings suggest that the face-inversion effect relies mainly on retinal coordinates, but that in head-down body-tilt orientations around 135 degrees the gravitational reference frame has a major influence on the perception of faces.

  8. New motion illusion caused by pictorial motion lines.

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    Kawabe, Takahiro; Miura, Kayo

    2008-01-01

    Motion lines (MLs) are a pictorial technique used to represent object movement in a still picture. This study explored how MLs contribute to motion perception. In Experiment 1, we reported the creation of a motion illusion caused by MLs: random displacements of objects with MLs on each frame were perceived as unidirectional global motion along the pictorial motion direction implied by MLs. In Experiment 2, we showed that the illusory global motion in the peripheral visual field captured the perceived motion direction of random displacement of objects without MLs in the central visual field, and confirmed that the results in Experiment 1 did not stem simply from response bias, but resulted from perceptual processing. In Experiment 3, we showed that the spatial arrangement of orientation information rather than ML length is important for the illusory global motion. Our results indicate that the ML effect is based on perceptual processing rather than response bias, and that comparison of neighboring orientation components may underlie the determination of pictorial motion direction with MLs.

  9. The Enfacement Illusion Is Not Affected by Negative Facial Expressions.

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    Beck, Brianna; Cardini, Flavia; Làdavas, Elisabetta; Bertini, Caterina

    2015-01-01

    Enfacement is an illusion wherein synchronous visual and tactile inputs update the mental representation of one's own face to assimilate another person's face. Emotional facial expressions, serving as communicative signals, may influence enfacement by increasing the observer's motivation to understand the mental state of the expresser. Fearful expressions, in particular, might increase enfacement because they are valuable for adaptive behavior and more strongly represented in somatosensory cortex than other emotions. In the present study, a face was seen being touched at the same time as the participant's own face. This face was either neutral, fearful, or angry. Anger was chosen as an emotional control condition for fear because it is similarly negative but induces less somatosensory resonance, and requires additional knowledge (i.e., contextual information and social contingencies) to effectively guide behavior. We hypothesized that seeing a fearful face (but not an angry one) would increase enfacement because of greater somatosensory resonance. Surprisingly, neither fearful nor angry expressions modulated the degree of enfacement relative to neutral expressions. Synchronous interpersonal visuo-tactile stimulation led to assimilation of the other's face, but this assimilation was not modulated by facial expression processing. This finding suggests that dynamic, multisensory processes of self-face identification operate independently of facial expression processing.

  10. Enhancing the mirror illusion with transcranial direct current stimulation.

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    Jax, Steven A; Rosa-Leyra, Diana L; Coslett, H Branch

    2015-05-01

    Visual feedback has a strong impact on upper-extremity movement production. One compelling example of this phenomena is the mirror illusion (MI), which has been used as a treatment for post-stroke movement deficits (mirror therapy). Previous research indicates that the MI increases primary motor cortex excitability, and this change in excitability is strongly correlated with the mirror's effects on behavioral performance of neurologically-intact controls. Based on evidence that primary motor cortex excitability can also be increased using transcranial direct current stimulation (tDCS), we tested whether bilateral tDCS to the primary motor cortices (anode right-cathode left and anode left-cathode right) would modify the MI. We measured the MI using a previously-developed task in which participants make reaching movements with the unseen arm behind a mirror while viewing the reflection of the other arm. When an offset in the positions of the two limbs relative to the mirror is introduced, reaching errors of the unseen arm are biased by the reflected arm's position. We found that active tDCS in the anode right-cathode left montage increased the magnitude of the MI relative to sham tDCS and anode left-cathode right tDCS. We take these data as a promising indication that tDCS could improve the effect of mirror therapy in patients with hemiparesis. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. A phase mixing model for the frequency-doubling illusion.

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    Wielaard, James; Smith, R Theodore

    2013-10-01

    We introduce a temporal phase mixing model for a description of the frequency-doubling illusion (FDI). The model is generic in the sense that it can be set to refer to retinal ganglion cells, lateral geniculate cells, as well as simple cells in the primary visual cortex (V1). Model parameters, however, strongly suggest that the FDI originates in the cortex. The model shows how noise in the response phases of cells in V1, or in further processing of these phases, easily produces observed behavior of FDI onset as a function of spatiotemporal frequencies. It also shows how this noise can accommodate physiologically plausible spatial delays in comparing neural signals over a distance. The model offers an explanation for the disappearance of the FDI at sufficiently high spatial frequencies via increasingly correlated coding of neighboring grating stripes. Further, when the FDI is equated to vanishing perceptual discrimination between asynchronous contrast-reversal gratings, the model proposes the possibility that the FDI shows a resonance behavior at sufficiently high spatial frequencies, by which it is alternately perceived and not perceived in sequential temporal frequency bands.

  12. Do You Hear More Piano or Drum Sounds? An Auditory Version of the Solitaire Illusion.

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    Prpic, Valter; Luccio, Riccardo

    2016-10-03

    The solitaire illusion is an illusion of numerosity proposed by Frith and Frith. In the original version, an apparent number of elements was determined by the spatial arrangement of two kinds of elements (black and white marbles). In our study, an auditory version of the solitaire illusion was demonstrated. Participants were asked to judge if they perceived more drum or piano sounds. When half of the piano tones were perceived as lower in pitch than a drum sound and the other half higher, piano tones appeared to be arranged in small units, leading to numerosity underestimation. Conversely, when all piano tones were perceived to be higher in pitch than the drum sounds, they appeared to be arranged in a single large unit, leading to numerosity overestimation. Comparable to the visual version of the solitaire illusion, the clustering seems to be determined by Gestalt principles. In our auditory version, a clear reversal of the illusion (numerosity overestimation or underestimation) was observed when piano tones appeared to be arranged in a single large cluster or in several small clusters, respectively. © The Author(s) 2016.

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

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    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.

  14. How the Thatcher illusion reveals evolutionary differences in the face processing of primates.

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    Weldon, Kimberly B; Taubert, Jessica; Smith, Carolynn L; Parr, Lisa A

    2013-09-01

    Face recognition in humans is a complex cognitive skill that requires sensitivity to unique configurations of eyes, mouth, and other facial features. The Thatcher illusion has been used to demonstrate the importance of orientation when processing configural information within faces. Transforming an upright face so that the eyes and mouth are inverted renders the face grotesque; however, when this "Thatcherized" face is inverted, the effect disappears. Due to the use of primate models in social cognition research, it is important to determine the extent to which specialized cognitive functions like face processing occur across species. To date, the Thatcher illusion has been explored in only a few species with mixed results. Here, we used computerized tasks to examine whether nonhuman primates perceive the Thatcher illusion. Chimpanzees and rhesus monkeys were required to discriminate between Thatcherized and unaltered faces presented upright and inverted. Our results confirm that chimpanzees perceived the Thatcher illusion, but rhesus monkeys did not, suggesting species differences in the importance of configural information in face processing. Three further experiments were conducted to understand why our results differed from previously published accounts of the Thatcher illusion in rhesus monkeys.

  15. Processing of the Müller-Lyer illusion by a Grey parrot (Psittacus erithacus).

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    Pepperberg, Irene M; Vicinay, Jennifer; Cavanagh, Patrick

    2008-01-01

    Alex, a Grey parrot (Psittacus erithacus) who identifies the bigger or smaller of two objects by reporting its color or matter using a vocal English label and who states "none" if they do not differ in size, was presented with two-dimensional Müller-Lyer figures (Brentano form) in which the central lines were of contrasting colors. His responses to "What color bigger/ smaller?" demonstrated that he saw the standard length illusion in the Müller-Lyer figures in 32 of 50 tests where human observers would also see the illusion and reported the reverse direction only twice. He did not report the illusion when (a) arrows on the shafts were perpendicular to the shafts or closely approached perpendicularity, (b) shafts were 6 times thicker than the arrows, or (c) after being tested with multiple exposures conditions that also lessen or eliminate the illusion for human observers. These data suggest that parrot and human visual systems process the Müller-Lyer figure in analogous ways despite a 175-fold difference in the respective sizes of their brain volumes. The similarity in results also indicates that parrots with vocal abilities like Alex's can be reliably tested on visual illusions with paradigms similar to those used on human subjects.

  16. Directional organization and shape formation: New illusions and Helmholtz’s Square

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    Baingio ePinna

    2015-03-01

    Full Text Available According to Helmholtz’s Square illusion, a square appears wider when it is filled with vertical lines and higher when filled with horizontal lines (Helmholtz, 1866. Recently, Pinna (2010a demonstrat- ed that the grouping of small squares on the basis of the similarity principle influences also percep- tion of their shape and of the whole emerging shapes. The direction imparted by grouping is the main attribute that influences the shape by polarizing it in the same direction both globally and locally. The rectangle illusion is opposite to what expected on the basis of Helmholtz’s Square illusion. Aim of this work is to solve the antinomy between the two sets of illusions and to demonstrate a common explanation based on the interaction between different sources of directional organization. This was accomplished by introducing some new phenomena and through phenomenological experiments proving the role played by the directional shape organization in shape formation. According to our results, Helmholtz’s square illusion shows at least two synergistic sources of directional organization: the direction of the grouping of the lines due to their similarity of the luminance contrast and the di- rection of the grouping of the lines due to the good continuation.

  17. 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.

  18. Implementation and Assessment of an Intervention to Debias Adolescents against Causal Illusions

    Science.gov (United States)

    Barberia, Itxaso; Blanco, Fernando; Cubillas, Carmelo P.; Matute, Helena

    2013-01-01

    Researchers have warned that causal illusions are at the root of many superstitious beliefs and fuel many people’s faith in pseudoscience, thus generating significant suffering in modern society. Therefore, it is critical that we understand the mechanisms by which these illusions develop and persist. A vast amount of research in psychology has investigated these mechanisms, but little work has been done on the extent to which it is possible to debias individuals against causal illusions. We present an intervention in which a sample of adolescents was introduced to the concept of experimental control, focusing on the need to consider the base rate of the outcome variable in order to determine if a causal relationship exists. The effectiveness of the intervention was measured using a standard contingency learning task that involved fake medicines that typically produce causal illusions. Half of the participants performed the contingency learning task before participating in the educational intervention (the control group), and the other half performed the task after they had completed the intervention (the experimental group). The participants in the experimental group made more realistic causal judgments than did those in the control group, which served as a baseline. To the best of our knowledge, this is the first evidence-based educational intervention that could be easily implemented to reduce causal illusions and the many problems associated with them, such as superstitions and belief in pseudoscience. PMID:23967189

  19. Implementation and assessment of an intervention to debias adolescents against causal illusions.

    Directory of Open Access Journals (Sweden)

    Itxaso Barberia

    Full Text Available Researchers have warned that causal illusions are at the root of many superstitious beliefs and fuel many people's faith in pseudoscience, thus generating significant suffering in modern society. Therefore, it is critical that we understand the mechanisms by which these illusions develop and persist. A vast amount of research in psychology has investigated these mechanisms, but little work has been done on the extent to which it is possible to debias individuals against causal illusions. We present an intervention in which a sample of adolescents was introduced to the concept of experimental control, focusing on the need to consider the base rate of the outcome variable in order to determine if a causal relationship exists. The effectiveness of the intervention was measured using a standard contingency learning task that involved fake medicines that typically produce causal illusions. Half of the participants performed the contingency learning task before participating in the educational intervention (the control group, and the other half performed the task after they had completed the intervention (the experimental group. The participants in the experimental group made more realistic causal judgments than did those in the control group, which served as a baseline. To the best of our knowledge, this is the first evidence-based educational intervention that could be easily implemented to reduce causal illusions and the many problems associated with them, such as superstitions and belief in pseudoscience.

  20. The accentuation principle of visual organization and the illusion of musical suspension.

    Science.gov (United States)

    Pinna, Baingio; Sirigu, Luca

    2011-01-01

    The aim of this work is to demonstrate a new principle of grouping and shape formation that we called the accentuation principle, stating that, all else being equal, the elements tend to group in the same oriented direction of the element discontinuity placed within a whole set of continuous/homogeneous components. The discontinuous element is like an accent, i.e., a visual emphasis within a whole. We showed that this principle is independent from other gestalt principles. In fact, it shows vectorial properties not present in the other principles. It can be pitted against them. Furthermore, it is not only a grouping principle but it also influences shape formation, by inducing effects like the square/diamond and the rectangle illusions. Finally, the accentuation operates under stroboscopic conditions and manifests filling-in properties and long range effects. Through experimental phenomenology, it was shown that the accentuation principle can influence grouping and shape formation not only in space but also in time and, therefore, not only in vision but also in music perception. This was suggested by phenomenally linking visual and musical accents and by demonstrating a new illusion of musical suspension, related with its opposite effect, the downbeat illusion. This kind of illusions can be appreciated in two solo piano compositions respectively by Debussy and Chopin-Rêverie and Nocturne, op. 27 no. 1. Variations in the note where the accent is placed and in the kind of accent demonstrated their basic role in inducing the illusion of musical suspension.

  1. Mishaps, errors, and cognitive experiences: on the conceptualization of perceptual illusions

    Science.gov (United States)

    Zavagno, Daniele; Daneyko, Olga; Actis-Grosso, Rossana

    2015-01-01

    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. PMID:25918504

  2. Brain process for perception of the "out of the body" tactile illusion for virtual object interaction.

    Science.gov (United States)

    Lee, Hye Jin; Lee, Jaedong; Kim, Chi Jung; Kim, Gerard J; Kim, Eun-Soo; Whang, Mincheol

    2015-04-01

    "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).

  3. The Onset Time of the Ownership Sensation in the Moving Rubber Hand Illusion

    Science.gov (United States)

    Kalckert, Andreas; Ehrsson, H. H.

    2017-01-01

    The rubber hand illusion (RHI) is a perceptual illusion whereby a model hand is perceived as part of one’s own body. This illusion has been extensively studied, but little is known about the temporal evolution of this perceptual phenomenon, i.e., how long it takes until participants start to experience ownership over the model hand. In the present study, we investigated a version of the rubber hand experiment based on finger movements and measured the average onset time in active and passive movement conditions. This comparison enabled us to further explore the possible role of intentions and motor control processes that are only present in the active movement condition. The results from a large group of healthy participants (n = 117) showed that the illusion of ownership took approximately 23 s to emerge (active: 22.8; passive: 23.2). The 90th percentile occurs in both conditions within approximately 50 s (active: 50; passive: 50.6); therefore, most participants experience the illusion within the first minute. We found indirect evidence of a facilitatory effect of active movements compared to passive movements, and we discuss these results in the context of our current understanding of the processes underlying the moving RHI. PMID:28344566

  4. 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..

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

    Directory of Open Access Journals (Sweden)

    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.

  6. Field Dependence, Efficiency of Information Processing in Working Memory and Susceptibility to Orientation Illusions among Architects

    Directory of Open Access Journals (Sweden)

    Młyniec Agnieszka

    2016-04-01

    Full Text Available This study examined cognitive predictors of susceptibility to orientation illusions: Poggendorff, Ponzo, and Zöllner. It was assumed that lower efficiency of information processing in WM and higher field dependence are conducive to orientation illusions. 61 architects (30 women aged M = 29, +/- 1.6, and 49 university students (29 women aged M = 23.53, +/- 4.24, were tested with Witkin’s EFT to assess their field dependence; the SWATT method was used as a measure of WM efficiency, and susceptibility to visual illusions was verified with a series of computer tasks. We obtained a small range of the explained variance in the regression models including FDI and WM indicators. On the basis of WM efficiency indicators, we managed to confirm the existence of memory predictors of susceptibility to illusions (they are rather weak, as they explain from 6% to 14% of the variance of the dependent variable. Among the architects, lower efficiency of WM processing (weaker inhibition, task-switching and higher field dependence are responsible for greater susceptibility to orientation illusions.

  7. Mishaps, errors, and cognitive experiences: on the conceptualization of perceptual illusions.

    Science.gov (United States)

    Zavagno, Daniele; Daneyko, Olga; Actis-Grosso, Rossana

    2015-01-01

    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.

  8. Dentists make larger holes in teeth than they need to if the teeth present a visual illusion of size.

    Directory of Open Access Journals (Sweden)

    Robert P O'Shea

    Full Text Available BACKGROUND: Health care depends, in part, on the ability of a practitioner to see signs of disease and to see how to treat it. Visual illusions, therefore, could affect health care. Yet there is very little prospective evidence that illusions can influence treatment. We sought such evidence. METHODS AND RESULTS: We simulated treatment using dentistry as a model system. We supplied eight, practicing, specialist dentists, endodontists, with at least 21 isolated teeth each, randomly sampled from a much larger sample of teeth they were likely to encounter. Teeth contained holes and we asked the endodontists to cut cavities in preparation for filling. Each tooth presented a more or less potent version of a visual illusion of size, the Delboeuf illusion, that made the holes appear smaller than they were. Endodontists and the persons measuring the cavities were blind to the parameters of the illusion. We found that the size of cavity endodontists made was linearly related to the potency of the Delboeuf illusion (p<.01 with an effect size (Cohen's d of 1.41. When the illusion made the holes appear smaller, the endodontists made cavities larger than needed. CONCLUSIONS: The visual context in which treatment takes place can influence the treatment. Undesirable effects of visual illusions could be counteracted by a health practitioner's being aware of them and by using measurement.

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

    Science.gov (United States)

    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.

  10. Multisensory integration in hemianopia and unilateral spatial neglect: Evidence from the sound induced flash illusion.

    Science.gov (United States)

    Bolognini, Nadia; Convento, Silvia; Casati, Carlotta; Mancini, Flavia; Brighina, Filippo; Vallar, Giuseppe

    2016-07-01

    Recent neuropsychological evidence suggests that acquired brain lesions can, in some instances, abolish the ability to integrate inputs from different sensory modalities, disrupting multisensory perception. We explored the ability to perceive multisensory events, in particular the integrity of audio-visual processing in the temporal domain, in brain-damaged patients with visual field defects (VFD), or with unilateral spatial neglect (USN), by assessing their sensitivity to the 'Sound-Induced Flash Illusion' (SIFI). The study yielded two key findings. Firstly, the 'fission' illusion (namely, seeing multiple flashes when a single flash is paired with multiple sounds) is reduced in both left- and right-brain-damaged patients with VFD, but not in right-brain-damaged patients with left USN. The disruption of the fission illusion is proportional to the extent of the occipital damage. Secondly, a reliable 'fusion' illusion (namely, seeing less flashes when a single sound is paired with multiple flashes) is evoked in USN patients, but neither in VFD patients nor in healthy participants. A control experiment showed that the fusion, but not the fission, illusion is lost in older participants (>50 year-old), as compared with younger healthy participants (illusions are dissociable multisensory phenomena, altered differently by impairments of visual perception (i.e. VFD) and spatial attention (i.e. USN). The occipital cortex represents a key cortical site for binding auditory and visual stimuli in the SIFI, while damage to right-hemisphere areas mediating spatial attention and awareness does not prevent the integration of audio-visual inputs in the temporal domain.

  11. Connectedness underlies the underestimation of the horizontal vertical illusion in L-shaped configurations.

    Science.gov (United States)

    Cai, Yongchun; Wang, Ci; Song, Chao; Li, Zhi

    2017-05-01

    L-shaped configuration is a commonly used stimulus configuration in studying horizontal vertical illusion. Here, we report that the horizontal vertical illusion is substantially underestimated when the L-shaped configuration is used for evaluating the illusion. Experiment 1 found that, in a length perception task, the perceived length of a vertical bar was about 10% longer than that of a horizontal bar with the same physical size. Similar amount of HVI was found in a length comparison task, in which the length of a horizontal bar was compared to that of a vertical bar and the two bars were presented separately in space or in time. In contrast, when the length comparison task was conducted with the two bars being arranged in a connected L-shape, the illusion was halved in strength. Experiment 2 and 3 studied what might be the cause of this L-shape induced HVI-underestimation. Two factors were investigated: the connectedness of the two lines, and the 45° absolute orientation or the 45° inner angle information embedded in the upright isosceles L-shape. The results showed that the HVI strength was not much affected when the 45° absolute orientation and the 45° angle information was made useless for the length comparison task. In contrast, the illusion was significantly reduced in strength whenever the two lines were separated as compared to when they were connected. These results suggested that the connectedness of the two lines must underlie the underestimation of the horizontal vertical illusion in the L-shaped configurations.

  12. The illusion of control and the importance of community in health care organizations.

    Science.gov (United States)

    Pitts, T

    1993-01-01

    The complexity of our health care environment and organizations requires a management style that moves beyond control to empowerment. Even though this complexity minimizes our ability to control events, many organizations are still preoccupied with the illusion of control. This restrains the performance of our health care organizations. Some of the contributing factors supporting this illusion are bureaucracy, scientific methodology, individualism, and our confusion of management with leadership. The concept of "community" is discussed from an organizational perspective. It is suggested that we can improve the performance of our organizations by rediscovering the values of community.

  13. Limitations of the Oriented Difference of Gaussian Filter in Special Cases of Brightness Perception Illusions.

    Science.gov (United States)

    Bakshi, Ashish; Roy, Sourya; Mallick, Arijit; Ghosh, Kuntal

    2016-03-01

    The Oriented Difference of Gaussian (ODOG) filter of Blakeslee and McCourt has been successfully employed to explain several brightness perception illusions which include illusions of both brightness-contrast type, for example, Simultaneous Brightness Contrast and Grating Induction and the brightness-assimilation type, for example, the White effect and the shifted White effect. Here, we demonstrate some limitations of the ODOG filter in predicting perceived brightness by comparing the ODOG responses to various stimuli (generated by varying two parameters, namely, test patch length and spatial frequency) with experimental observations of the same.

  14. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  16. Rumination and interoceptive accuracy predict the occurrence of the thermal grill illusion of pain

    OpenAIRE

    Scheuren, Raymonde; Sütterlin, Stefan; Anton, Fernand

    2014-01-01

    Background: While the neurophysiological mechanisms underlying the thermal grill illusion of pain (TGI) have been thoroughly studied, psychological determinants largely remain unknown. The present study aimed to investigate whether cognitive and affective personality traits encompassing rumination, interoception, and suggestibility may be identified as characteristics favouring the elicitation of paradoxical pain experiences. Methods: The dominant hand of 54 healthy volunteers was...

  17. Perceptual and Decisional Factors Influencing the Discrimination of Inversion in the Thatcher Illusion

    Science.gov (United States)

    Cornes, Katherine; Donnelly, Nick; Godwin, Hayward; Wenger, Michael J.

    2011-01-01

    The Thatcher illusion (Thompson, 1980) is considered to be a prototypical illustration of the notion that face perception is dependent on configural processes and representations. We explored this idea by examining the relative contributions of perceptual and decisional processes to the ability of observers to identify the orientation of two…

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

    DEFF Research Database (Denmark)

    Engsted, Tom; Pedersen, Thomas Quistgaard

    In long-term US data the stock market dividend yield is a strong predictor of long-horizon inflation with a negative slope coefficient. This finding is puzzling in light of the traditional Modigliani-Cohn money illusion hypothesis according to which the dividend yield varies positively with expec...

  19. Remembering Makes Evidence Compelling: Retrieval from Memory Can Give Rise to the Illusion of Truth

    Science.gov (United States)

    Ozubko, Jason D.; Fugelsang, Jonathan

    2011-01-01

    The "illusion of truth" is traditionally described as the increase in perceived validity of statements when they are repeated (Hasher, Goldstein, & Toppino, 1977). However, subsequent work has demonstrated that the effect can arise due to the increased familiarity or fluency afforded by repetition and not necessarily to repetition…

  20. Remembering Makes Evidence Compelling: Retrieval from Memory Can Give Rise to the Illusion of Truth

    Science.gov (United States)

    Ozubko, Jason D.; Fugelsang, Jonathan

    2011-01-01

    The "illusion of truth" is traditionally described as the increase in perceived validity of statements when they are repeated (Hasher, Goldstein, & Toppino, 1977). However, subsequent work has demonstrated that the effect can arise due to the increased familiarity or fluency afforded by repetition and not necessarily to repetition…

  1. The criminal profiling illusion : What’s Behind the Smoke and Mirrors?

    NARCIS (Netherlands)

    Snook, Brent; Cullen, Richard M.; Bennell, Craig; Taylor, Paul J.; Gendreau, Paul

    2008-01-01

    There is a belief that criminal profilers can predict a criminal's characteristics from crime scene evidence. In this article, the authors argue that this belief may be an illusion and explain how people may have been misled into believing that criminal profiling (CP) works despite no sound

  2. 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

  3. Defining filled and empty space: reassessing the filled space illusion for active touch and vision.

    Science.gov (United States)

    Collier, Elizabeth S; Lawson, Rebecca

    2016-09-01

    In the filled space illusion, an extent filled with gratings is estimated as longer than an equivalent extent that is apparently empty. However, researchers do not seem to have carefully considered the terms filled and empty when describing this illusion. Specifically, for active touch, smooth, solid surfaces have typically been used to represent empty space. Thus, it is not known whether comparing gratings to truly empty space (air) during active exploration by touch elicits the same illusionary effect. In Experiments 1 and 2, gratings were estimated as longer if they were compared to smooth, solid surfaces rather than being compared to truly empty space. Consistent with this, Experiment 3 showed that empty space was perceived as longer than solid surfaces when the two were compared directly. Together these results are consistent with the hypothesis that, for touch, the standard filled space illusion only occurs if gratings are compared to smooth, solid surfaces and that it may reverse if gratings are compared to empty space. Finally, Experiment 4 showed that gratings were estimated as longer than both solid and empty extents in vision, so the direction of the filled space illusion in vision was not affected by the nature of the comparator. These results are discussed in relation to the dual nature of active touch.

  4. Charity donations and the Euro introduction: some quasi-experimental evidence on money illusion

    NARCIS (Netherlands)

    Kooreman, P.; Faber, R.; Hofmans, H.

    2004-01-01

    We compare the revenues of a house-to-house collection for a charity before and after the introduction of the euro in a ceteris paribus setting. We find strong evidence of money illusion, supplementing earlier econometric, experimental, and survey evidence on its existence.

  5. Illusory Tactile Motion Perception: An Analog of the Visual Filehne Illusion.

    Science.gov (United States)

    Moscatelli, Alessandro; Hayward, Vincent; Wexler, Mark; Ernst, Marc O

    2015-09-28

    We continually move our body and our eyes when exploring the world, causing our sensory surfaces, the skin and the retina, to move relative to external objects. In order to estimate object motion consistently, an ideal observer would transform estimates of motion acquired from the sensory surface into fixed, world-centered estimates, by taking the motion of the sensor into account. This ability is referred to as spatial constancy. Human vision does not follow this rule strictly and is therefore subject to perceptual illusions during eye movements, where immobile objects can appear to move. Here, we investigated whether one of these, the Filehne illusion, had a counterpart in touch. To this end, observers estimated the movement of a surface from tactile slip, with a moving or with a stationary finger. We found the perceived movement of the surface to be biased if the surface was sensed while moving. This effect exemplifies a failure of spatial constancy that is similar to the Filehne illusion in vision. We quantified this illusion by using a Bayesian model with a prior for stationarity, applied previously in vision. The analogy between vision and touch points to a modality-independent solution to the spatial constancy problem.

  6. Coolness both underlies and protects against the painfulness of the thermal grill illusion.

    Science.gov (United States)

    Harper, Daniel E; Hollins, Mark

    2014-04-01

    We investigated the contributions of warm and cool signals in generating the thermal grill illusion (TGI), a phenomenon in which interlaced warm and cool bars generate an experience of burning, and under some conditions painful, heat. Each subject underwent 3 runs, 2 of which tested the effects of preadapting subjects to the grill's warm or cool bars (while the interlaced bars were thermally neutral) on the subsequent intensity of the illusion. In a control run, all bars were neutral during the adaptation phase. Thermal visual analogue scale ratings during the warm and cool adaptation periods revealed significant and equivalent adaptation to the 2 temperatures. Adaptation to the grill's cool bars significantly reduced pain and perceived thermal intensity of the TGI, compared to the control condition, while adaptation to the grill's warm bars had little effect. These results suggest that the cool stimulus triggers the pain signals that produce the illusion. The inability of warm adaptation to attenuate the TGI is at odds with theories suggesting that the illusion depends upon a simple addition of warm and cool signals. While the grill's cool bars are necessary for the TGI's painfulness, we also observed that the more often a participant reported feeling coolness or coldness, the less pain he or she experienced from the TGI. These results are consistent with research showing that cool temperatures generate activity in both thermoreceptive-specific, pain-inhibitory neurons and nociceptive dorsal horn neurons.

  7. Factors affecting the haptic filled-space illusion for dynamic touch

    NARCIS (Netherlands)

    Sanders, A.F.J.; Kappers, A.M.L.

    2009-01-01

    In the haptic filled-space illusion for active dynamic touch, observers move their fingertip across an unfilled extent or an extent filled with intermediate stimulations. Previous researchers have reported lengths of filled extents to be overestimated, but the parameters affecting the strength of th

  8. 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…

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

    NARCIS (Netherlands)

    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 lan

  10. The Vanishing Ball Illusion: A new perspective on the perception of dynamic events.

    Science.gov (United States)

    Kuhn, Gustav; Rensink, Ronald A

    2016-03-01

    Our perceptual experience is largely based on prediction, and as such can be influenced by knowledge of forthcoming events. This susceptibility is commonly exploited by magicians. In the Vanishing Ball Illusion, for example, a magician tosses a ball in the air a few times and then pretends to throw the ball again, whilst secretly concealing it in his hand. Most people claim to see the ball moving upwards and then vanishing, even though it did not leave the magician's hand (Kuhn & Land, 2006; Triplett, 1900). But what exactly can such illusions tell us? We investigated here whether seeing a real action before the pretend one was necessary for the Vanishing Ball Illusion. Participants either saw a real action immediately before the fake one, or only a fake action. Nearly one third of participants experienced the illusion with the fake action alone, while seeing the real action beforehand enhanced this effect even further. Our results therefore suggest that perceptual experience relies both on long-term knowledge of what an action should look like, as well as exemplars from the immediate past. In addition, whilst there was a forward displacement of perceived location in perceptual experience, this was not found for oculomotor responses, consistent with the proposal that two separate systems are involved in visual perception.

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

    Science.gov (United States)

    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.

  12. Fooling the eyes: the influence of a sound-induced visual motion illusion on eye movements.

    Directory of Open Access Journals (Sweden)

    Alessio Fracasso

    Full Text Available The question of whether perceptual illusions influence eye movements is critical for the long-standing debate regarding the separation between action and perception. To test the role of auditory context on a visual illusion and on eye movements, we took advantage of the fact that the presence of an auditory cue can successfully modulate illusory motion perception of an otherwise static flickering object (sound-induced visual motion effect. We found that illusory motion perception modulated by an auditory context consistently affected saccadic eye movements. Specifically, the landing positions of saccades performed towards flickering static bars in the periphery were biased in the direction of illusory motion. Moreover, the magnitude of this bias was strongly correlated with the effect size of the perceptual illusion. These results show that both an audio-visual and a purely visual illusion can significantly affect visuo-motor behavior. Our findings are consistent with arguments for a tight link between perception and action in localization tasks.

  13. 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…

  14. Holistic Processing of Faces as Measured by the Thatcher Illusion Is Intact in Autism Spectrum Disorders

    Science.gov (United States)

    Cleary, Laura; Brady, Nuala; Fitzgerald, Michael; Gallagher, Louise

    2015-01-01

    Impaired face perception in autism spectrum disorders is thought to reflect a perceptual style characterized by componential rather than configural processing of faces. This study investigated face processing in adolescents with autism spectrum disorders using the Thatcher illusion, a perceptual phenomenon exhibiting "inversion effects"…

  15. Differential Effects of the Rod-and-Frame Illusion on the Timing of Forearm Rotations

    NARCIS (Netherlands)

    Lommertzen, J.; Zuijlen, A.M.J. van; Meulenbroek, R.G.J.; Lier, R.J. van

    2009-01-01

    The present study focused on the time course of the effects of the Rod-and-Frame Illusion (RFI) on the kinematics of targeted forearm rotations. Participants were asked to reproduce perceived rod orientations by propelling a hand-held cylinder forward while rotating it to the target orientation. Rod

  16. The "Illusion of Life" Rhetorical Perspective: An Integrated Approach to the Study of Music as Communication.

    Science.gov (United States)

    Sellnow, Deanna; Sellnow, Timothy

    2001-01-01

    Suggests the "illusion of life" rhetorical perspective increases understanding about how discursive linguistic symbols and non-discursive aesthetic symbols function together to communicate and persuade in didactic music. Argues that lyrics and music work together to offer messages comprised of both conceptual and emotional content through the…

  17. Here's Looking at You: Visual Similarity Exacerbates the Moses Illusion for Semantically Similar Celebrities

    Science.gov (United States)

    Davis, Danielle K.; Abrams, Lise

    2016-01-01

    When people read questions like "How many animals of each kind did Moses take on the ark?", many mistakenly answer "2" despite knowing that Noah sailed the ark. This "Moses illusion" occurs when names share semantic features. Two experiments examined whether shared "visual" concepts (facial features)…

  18. Remembering Makes Evidence Compelling: Retrieval from Memory Can Give Rise to the Illusion of Truth

    Science.gov (United States)

    Ozubko, Jason D.; Fugelsang, Jonathan

    2011-01-01

    The "illusion of truth" is traditionally described as the increase in perceived validity of statements when they are repeated (Hasher, Goldstein, & Toppino, 1977). However, subsequent work has demonstrated that the effect can arise due to the increased familiarity or fluency afforded by repetition and not necessarily to repetition per se. We…

  19. Applying the Helmholtz illusion to fashion: horizontal stripes won't make you look fatter.

    Science.gov (United States)

    Thompson, Peter; Mikellidou, Kyriaki

    2011-01-01

    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.

  20. The Roles of Encoding and Retrieval Processes in Associative and Categorical Memory Illusions

    Science.gov (United States)

    Dewhurst, Stephen A.; Bould, Emma; Knott, Lauren M.; Thorley, Craig

    2009-01-01

    Four experiments investigated the origin of associative and categorical memory illusions by comparing the effects of study and test associations on Deese/Roediger-McDermott (DRM) and categorized lists. Experiments 1 and 2 found that levels of false recognition with both list types were increased by manipulations that facilitated the generation of…

  1. The Rubber Hand Illusion Reveals Proprioceptive and Sensorimotor Differences in Autism Spectrum Disorders

    Science.gov (United States)

    Paton, Bryan; Hohwy, Jakob; Enticott, Peter G.

    2012-01-01

    Autism spectrum disorder (ASD) is characterised by differences in unimodal and multimodal sensory and proprioceptive processing, with complex biases towards local over global processing. Many of these elements are implicated in versions of the rubber hand illusion (RHI), which were therefore studied in high-functioning individuals with ASD and a…

  2. 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.

  3. Ice cream illusions - Bowls, spoons, and self-served portion sizes

    NARCIS (Netherlands)

    Wansink, Brian; van Ittersum, Koert; Painter, James E.

    2006-01-01

    Background: Because people eat most of what they serve themselves, any contextual cues that lead them to over-serve should lead them to over-eat. In building on the size-contrast illusion, this research examines whether the size of a bowl or serving spoon unknowingly biases how much a person serves

  4. Enlarged temporal integration window in schizophrenia indicated by the double-flash illusion

    NARCIS (Netherlands)

    Haß, Katharina; Sinke, Christopher; Reese, Tanya; Roy, Mandy; Wiswede, Daniel; Dillo, Wolfgang; Oranje, Bob; Szycik, Gregor R.

    2017-01-01

    Introduction: In the present study we were interested in the processing of audio-visual integration in schizophrenia compared to healthy controls. The amount of sound-induced double-flash illusions served as an indicator of audio-visual integration. We expected an altered integration as well as a

  5. Measurement of eye size illusion caused by eyeliner, mascara, and eye shadow.

    Science.gov (United States)

    Matsushita, Soyogu; Morikawa, Kazunori; Yamanami, Haruna

    2015-01-01

    Do eyeliner, mascara, and eye shadow actually make the eyes appear larger than they really are? If so, by what percentage? To answer these questions, we used psychophysical experiments. Experiment 1 manipulated the degree of eyeliner (four levels) and mascara (five levels), and measured perceived eye size using a psychophysical procedure called the staircase method. The results showed that both eyeliner and mascara make the eyes appear larger than they really are by up to 6% (13% in area), but their effects are not additive. Eyeliner increased perceived eye size only in the absence of mascara. In the presence of mascara, however, eyeliner has no additional effect. Experiment 2 measured perceived eye size with or without eye shadow and demonstrated that eye shadow increases perceived eye size by about 5% (10% in area). These findings indicate that one mechanism by which makeup and cosmetics alter facial appearances involves inducing visual illusions. In addition, it is suggested that the eye size illusion caused by eyeliner, mascara, and eye shadow uses the same mechanism as that of the Delboeuf illusion, a geometric illusion of assimilation.

  6. Nous, animaux fabulateurs et nos technologies de l’illusion

    Directory of Open Access Journals (Sweden)

    Lorenzo Soccavo

    2014-12-01

    Full Text Available La propagation plastique des mythes au sein des civilisations humaines et au fil du temps inscrit leur puissance mémétique dans la conscience des hommes. Nous sommes pris dans le filet tissé par l’évolutionnisme et le créationnisme, deux récits qui présupposent, pour le premier une loi immanente, pour le second une loi transcendante. Ce dualisme là est opérant, il bipolarise comme tout ce qui relève d’une double nature. La pensée mythique s’y originerait dans la faculté exceptionnelle du langage humain à se découpler du réel et à se référer à des réalités de l’espace intérieur et non plus du monde extérieur. L’animal fabulateur qu’est l’être humain a toujours inventé des machines à produire des simulacres, les récits mythiques et les livres en sont. Or, ces technologies de l’illusion fonctionnent trop bien. Elles nous maintiennent dans la croyance que ce que nous appelons du nom de “Réel” serait dans les réalités extérieures. Davantage qu’une matrice sémantique, le corpus mythique doit être envisagé comme une grossesse : un état transitoire entre un moment passé de fécondation, et celui, encore à venir de l’accouchement. Et là où la mythanalyse pourrait se concevoir comme une navigation pour remonter à la source d’un fleuve, la prospective de la lecture s’offre elle comme la quête d’un détroit de Magellan vers un océan intérieur : deux approches complémentaires pour les animaux fabulateurs que nous sommes.

  7. Georges Sagnac: A life for optics

    Science.gov (United States)

    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"

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Science.gov (United States)

    Apthorp, Deborah; Nagle, Fintan; Palmisano, Stephen

    2014-01-01

    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.

  11. The invisibility cloak illusion: People (incorrectly) believe they observe others more than others observe them.

    Science.gov (United States)

    Boothby, Erica J; Clark, Margaret S; Bargh, John A

    2017-04-01

    Whether at a coffee shop, in a waiting room, or riding the bus, people frequently observe the other people around them. Yet they often fail to realize how much other people engage in the same behavior, and that they, therefore, also are being observed. Because it is logically impossible that people, on average, are the subjects of observation more than they are objects of it, the belief that one watches others more than one is watched is an illusion. Several studies show that people incorrectly believe that they observe others more than other people observe them. We call this mistaken belief the "invisibility cloak illusion." People believe that they observe others more than do other people and that they are generally observed less than are others (Studies 1-3, 5, 6). The illusion persists both among strangers in the same vicinity (Study 2) and among friends interacting with one another (Study 3), and it cannot be explained away as yet another general better-than-average bias nor is it the result of believing one has more thoughts, in general, than do other people (Studies 2-3). The illusion is supported by a failure to catch others watching oneself (Studies 1b, 4) and it is manifest in the specific contents of people's thoughts about one another (Studies 5 and 6). Finally, rendering a feature of one's appearance salient to oneself fails to interrupt the illusion despite increasing one's belief that others are paying more attention specifically to that salient feature (Study 6). (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  12. 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.

  13. A sensational illusion: vision-touch synaesthesia and the rubber hand paradigm.

    Science.gov (United States)

    Aimola Davies, Anne M; White, Rebekah C

    2013-03-01

    For individuals with vision-touch synaesthesia, the sight of touch on another person elicits synaesthetic tactile sensation on the observer's own body. Here we used the traditional rubber hand paradigm (Botvinick and Cohen, 1998) and a no-touch rubber hand paradigm to investigate and to authenticate synaesthetic tactile sensation. In the traditional rubber hand paradigm, the participant views a prosthetic hand being touched by the Examiner while the participant's hand - hidden from view - is also touched by the Examiner. Synchronous stimulation of the prosthetic hand and the participant's hidden hand elicits the rubber hand illusion. It may seem to the participant that she is feeling touch at the location of the viewed prosthetic hand - visual capture of touch, and that the prosthetic hand is the participant's own hand - illusion of ownership. Thus, for participants who experience the traditional rubber hand illusion, tactile sensation on the participant's hidden hand is referred to the prosthetic hand. In our no-touch rubber hand paradigm, the participant views a prosthetic hand being touched by the Examiner but the participant's hand - hidden from view - is not touched by the Examiner. Questionnaire ratings indicated that only individuals with vision-touch synaesthesia experienced the no-touch rubber hand illusion. Thus, synaesthetic tactile sensation on the (untouched) hidden hand was referred to the prosthetic hand. These individuals also demonstrated proprioceptive drift (a change, from baseline, in proprioceptively perceived position) of the hidden hand towards the location of the prosthetic hand, and a pattern of increased proprioceptive drift with increased trial duration (60 sec, 180 sec, 300 sec). The no-touch rubber hand paradigm was an excellent method to authenticate vision-touch synaesthesia because participants were naïve about the rubber hand illusion, and they could not have known how they were expected to perform on either the traditional or the

  14. Size matters: a single representation underlies our perceptions of heaviness in the size-weight illusion.

    Directory of Open Access Journals (Sweden)

    Gavin Buckingham

    Full Text Available In the size-weight illusion (SWI, a small object feels heavier than an equally-weighted larger object. It is thought that this illusion is a consequence of the way that we internally represent objects' properties--lifters expect one object to outweigh the other, and the subsequent illusion reflects a contrast with their expectations. Similar internal representations are also thought to guide the application of fingertip forces when we grip and lift objects. To determine the nature of the representations underpinning how we lift objects and perceive their weights, we examined weight judgments in addition to the dynamics and magnitudes of the fingertip forces when individuals lifted small and large exemplars of metal and polystyrene cubes, all of which had been adjusted to have exactly the same mass. Prior to starting the experiment, subjects expected the density of the metal cubes to be higher than that of the polystyrene cubes. Their illusions, however, did not reflect their conscious expectations of heaviness; instead subjects experienced a SWI of the same magnitude regardless of the cubes' material. Nevertheless, they did report that the polystyrene cubes felt heavier than the metal ones (i.e. they experienced a material-weight illusion. Subjects persisted in lifting the large metal cube with more force than the small metal cube, but lifted the large polystyrene cube with roughly the same amount of force that they used to lift the small polystyrene cube. These findings suggest that our perceptual and sensorimotor representations are not only functionally independent from one another, but that the perceptual system represents a more single, simple size-weight relationship which appears to drive the SWI itself.

  15. 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

    Full Text Available BACKGROUND: 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. METHODOLOGY/PRINCIPAL FINDINGS: 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. CONCLUSIONS/SIGNIFICANCE: 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

  16. Personality traits and perception of Müller-Lyer illusion in male Chinese military soldiers and university students

    National Research Council Canada - National Science Library

    Yingchun Zhang; Jing Liu; Yongli Wang; Jingyi Huang; Lili Wei; Bingren Zhang; Wei Wang; Wei Chen

    2017-01-01

    In military men, performance such as gun-shooting precision relies on factors such as the ability to resist visual illusion, and this misperception of visual stimulus might be linked with sensation...

  17. 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.

  18. 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.

  19. Broadband phase-preserved optical elevator

    CERN Document Server

    Luo, Yuan; Zhang, Baile; Qiu, Cheng-Wei; Barbastathis, George

    2011-01-01

    Phase-preserved optical elevator is an optical device to lift up an entire plane virtually without distortion in light path or phase. Using transformation optics, we have predicted and observed the realization of such a broadband phase-preserved optical elevator, made of a natural homogeneous birefringent crystal without resorting to absorptive and narrowband metamaterials involving time-consuming nano-fabrication. In our demonstration, the optical elevator is designed to lift a sheet upwards, and the phase is verified to be preserved always. The camouflage capability is also demonstrated in the presence of adjacent objects of the same scale at will. The elevating device functions in different surrounding media over the wavelength range of 400-700 nm. Our work opens up prospects for studies of light trapping, solar energy, illusion optics, communication, and imaging.

  20. How illusory is the solitaire illusion? Assessing the degree of misperception of numerosity in adult humans

    Directory of Open Access Journals (Sweden)

    Christian Agrillo

    2016-10-01

    Full Text Available The Solitaire illusion occurs when the spatial arrangement of items influences the subjective estimation of their quantity. Unlike other illusory phenomena frequently reported in humans and often also in non-human animals, evidence of the Solitaire illusion in species other than humans remains weak. However, before concluding that this perceptual bias affects quantity judgments differently in human and non-human animals, further investigations on the strength of the Solitaire illusion is required. To date, no study has assessed the exact misperception of numerosity generated by the Solitaire arrangement, and the possibility exists that the numerical effects generated by the illusion are too subtle to be detected by non-human animals.The present study investigated the strength of this illusion in adult humans. In a relative numerosity task, participants were required to select which array contained more blue items in the presence of two arrays made of identical blue and yellow items. Participants perceived the Solitaire illusion as predicted, overestimating the Solitaire array with centrally clustered blue items as more numerous than the Solitaire array with blue items on the perimeter. Their performance in the presence of the Solitaire array was similar to that observed in control trials with numerical ratios larger than 0.67, suggesting that the illusory array produces a substantial overestimation of the number of blue items in one array relative to the other. This aspect was more directly investigated in a numerosity identification task in which participants were required to estimate the number of blue items when single arrays were presented one at a time. In the presence of the Solitaire array, participants slightly overestimated the number of items when they were centrally located while they underestimated the number of items when those items were located on the perimeter. Items located on the perimeter were perceived to be 76% as numerous

  1. Simulation of vestibular flight illusions on the ground%前庭性飞行错觉地面模拟

    Institute of Scientific and Technical Information of China (English)

    黄炜; 于立身; 季思菊; 李交杰; 张刚林; 黄佳怡; 马志超

    2012-01-01

    Objective To promote the pilot's experience on vestibular flight illusions under simulated flying environment and to investigate the illusion induced rate and the result of vestibular illusion simulation on the ground.Methods Forty-six pilots experienced vestibular flight illusions by the simulator that was according to the mechanism of generating vestibular flight illusions.The orientation feeling,feedback of personal state,response of autonomic nervous system and the evaluation of training effect were recorded.Results The total vestibular illusion induced rate was 91.7%.The induced rate of absence of rotation illusion,opposite-rotation illusion,Coriolis illusion,somatogravic illusion,G-excess illusion and nystagmus effect was respectively 100.0%,100.0%,91.7%,78.6%,94.4% and 100.0%.All pilots reported experienced vestibular flight illusions.In the analysis of assessing induced acute motion sickness only 4 person-times showed transient reflex at MⅡ level,and no reflex more severe than M Ⅲ or MS level was observed.Pilots assessed such experience was helpful in knowing illusions and preventing spatial disorientation accidents.Conclusion The flight illusion simulator can effectively keep pilots experiencing flight vestibular illusions upon high induced rate,proper stimulation and notable effects.%目的 让飞行员在地面上体验模拟飞行条件下的前庭性飞行错觉,观察错觉的诱发率和地面模拟前庭性飞行错觉的效果. 方法 根据前庭性飞行错觉的发生机制,利用飞行错觉模拟器模拟飞行错觉.46名歼(强)击机飞行员进行错觉体验,记录其空间感觉主诉、对自身状态的反馈、自主神经反应及对训练效果的评价. 结果 前庭性错觉总诱发率为91.7%;不旋转错觉诱发率100.0%,反旋转错觉100.0%,Coriolis错觉91.7%,躯体重力错觉78.6%,超重错觉94.4%,眼震效应100.0%.本组飞行员错觉体验率为100.0%.在飞行错觉体验过程

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

    Science.gov (United States)

    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.

  3. Mind Reading in Stage Magic: The “Second Sight” Illusion, Media, and Mediums

    Directory of Open Access Journals (Sweden)

    Katharina Rein

    2015-09-01

    Full Text Available This article analyzes the late-nineteenth-century stage illusion “The Second Sight,” which seemingly demonstrates the performers’ telepathic abilities. The illusion is on the one hand regarded as an expression of contemporary trends in cultural imagination as it seizes upon notions implied by spiritualism as well as utopian and dystopian ideas associated with technical media. On the other hand, the spread of binary code in communication can be traced along with the development of the "Second Sight," the latter being outlined by means of three examples using different methods to obtain a similar effect. While the first version used a speaking code to transmit information, the other two were performed silently, relying on other ways of communication. The article reveals how stage magic, technical media, spiritualism, and mind reading were interconnected in the late nineteenth century, and drove each other forward.

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

    Directory of Open Access Journals (Sweden)

    Christine Veras

    2017-03-01

    Full Text Available 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.

  5. The moon illusion and size-distance scaling--evidence for shared neural patterns.

    Science.gov (United States)

    Weidner, Ralph; Plewan, Thorsten; Chen, Qi; Buchner, Axel; Weiss, Peter H; Fink, Gereon R

    2014-08-01

    A moon near to the horizon is perceived larger than a moon at the zenith, although--obviously--the moon does not change its size. In this study, the neural mechanisms underlying the "moon illusion" were investigated using a virtual 3-D environment and fMRI. Illusory perception of an increased moon size was associated with increased neural activity in ventral visual pathway areas including the lingual and fusiform gyri. The functional role of these areas was further explored in a second experiment. Left V3v was found to be involved in integrating retinal size and distance information, thus indicating that the brain regions that dynamically integrate retinal size and distance play a key role in generating the moon illusion.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Science.gov (United States)

    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).

  8. Helmholtz illusion makes you look fit only when you are already fit, but not for everyone.

    Science.gov (United States)

    Ashida, Hiroshi; Kuraguchi, Kana; Miyoshi, Kiyofumi

    2013-01-01

    A square filled with horizontal stripes is perceived as thinner than one with vertical stripes (Helmholtz illusion). This is not consistent with a common belief that horizontally striped clothing makes a person look fatter, and studies on this problem have shown inconsistent results. Here, we demonstrate three factors that could have complicated the issue. First, the Helmholtz effect is stronger for a thin figure than for a fat one, with possible reversal for the latter. Second, we found large variability across participants, suggesting dependence on features to attend. Third, there was strong hysteresis as to the order of testing fat and thin figures, suggesting the effect of surrounding people in daily life. There can be yet other factors, but we should note that this apparently simple case of application of a geometrical illusion in daily perception should be taken as a rather complex phenomenon.

  9. 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.

  10. Orientation enhancement in early visual processing can explain time course of brightness contrast and White's illusion.

    Science.gov (United States)

    Karmakar, Subhajit; Sarkar, Sandip

    2013-06-01

    Dynamics of orientation tuning in V1 indicates that computational model of V1 should not only comprise of bank of static spatially oriented filters but also include the contribution for dynamical response facilitation or suppression along orientation. Time evolution of orientation response in V1 can emerge due to time- dependent excitation and lateral inhibition in the orientation domain. Lateral inhibition in the orientation domain suggests that Ernst Mach's proposition can be applied for the enhancement of initial orientation distribution that is generated due to interaction of visual stimulus with spatially oriented filters and subcortical temporal filter. Oriented spatial filtering that appears much early (explain experimentally observed temporal dynamics of brightness contrast illusion. But, enhancement of orientation response at early phase of visual processing is the key mechanism that can guide visual system to predict the brightness by "Max-rule" or "Winner Takes All" (WTA) estimation and thus producing White's illusions at any exposure.

  11. Scoring men: vasectomies and the totemic illusion of male sexuality in Oaxaca.

    Science.gov (United States)

    Gutmann, Matthew C

    2005-03-01

    This paper discusses research on men's reproductive health and sexuality in Oaxaca, Mexico, and specifically why some men there choose to be sterilized. Men who opt for vasectomies do so after considering numerous cultural, historical, physiological, commercial, and other concerns. Men and women in Oaxaca negotiate certain cultural folk beliefs about supposed male sexual desires and practices before arriving at the decision to get the operation. Vasectomy as a method of birth control is chosen despite folk beliefs that take the form of a totemic illusion which treats male sexuality as naturalized, something fixed, and as entirely distinct from female sexuality. Among its many consequences, this totemic illusion serves to conceal inequalities in the sphere of reproductive health and sexuality in relation to contraception.

  12. Aniseikonia Tests: The Role of Viewing Mode, Response Bias, and Size–Color Illusions

    Science.gov (United States)

    García-Pérez, Miguel A.; Peli, Eli

    2015-01-01

    Purpose: To identify the factors responsible for the poor validity of the most common aniseikonia tests, which involve size comparisons of red–green stimuli presented haploscopically. Methods: Aniseikonia was induced by afocal size lenses placed before one eye. Observers compared the sizes of semicircles presented haploscopically via color filters. The main factor under study was viewing mode (free viewing versus short presentations under central fixation). To eliminate response bias, a three-response format allowed observers to respond if the left, the right, or neither semicircle appeared larger than the other. To control decisional (criterion) bias, measurements were taken with the lens-magnified stimulus placed on the left and on the right. To control for size–color illusions, measurements were made with color filters in both arrangements before the eyes and under binocular vision (without color filters). Results: Free viewing resulted in a systematic underestimation of lens-induced aniseikonia that was absent with short presentations. Significant size–color illusions and decisional biases were found that would be mistaken for aniseikonia unless appropriate action is taken. Conclusions: To improve their validity, aniseikonia tests should use short presentations and include control conditions to prevent contamination from decisional/response biases. If anaglyphs are used, presence of size–color illusions must be checked for. Translational relevance: We identified optimal conditions for administration of aniseikonia tests and appropriate action for differential diagnosis of aniseikonia in the presence of response biases or size–color illusions. Our study has clinical implications for aniseikonia management. PMID:26101722

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

    Directory of Open Access Journals (Sweden)

    Antonella eMaselli

    2014-09-01

    Full Text Available 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

  14. Temporal Binding Window of the Sound-Induced Flash Illusion in Amblyopia.

    Science.gov (United States)

    Narinesingh, Cindy; Goltz, Herbert C; Wong, Agnes M F

    2017-03-01

    Amblyopia is a neurodevelopmental visual disorder caused by abnormal visual experience in childhood. In addition to known visual deficits, there is evidence for changes in audiovisual integration in amblyopia using explicit tasks. We examined audiovisual integration in amblyopia using an implicit task that is more relevant in a real-world context. A total of 11 participants with amblyopia and 16 controls were tested binocularly and monocularly on the sound-induced flash illusion, in which flashes and beeps are presented concurrently and the perceived number of flashes is influenced by the number of beeps. The task used 1 to 2 rapid peripheral flashes presented with 0 to 2 beeps, at 5 stimulus onset asynchronies, that is, beep (-200 milliseconds, -100 milliseconds) or flash leading (100 milliseconds, 200 milliseconds) or simultaneous (0 milliseconds). Participants reported the number of perceived flashes. Susceptibility was indicated by a "2 flashes" response to "fission" (1 flash, 2 beeps) or "1 flash" to "fusion" (2 flashes, 1 beep). For fission with the beep leading during binocular viewing, controls showed an expected decrease in illusion strength as stimulus onset asynchronies increased, whereas the illusion strength remained constant in participants with amblyopia, indicating a wider temporal binding window in amblyopia (P = 0.007). For fusion, participants with amblyopia showed reduced illusion strength during amblyopic eye viewing (P = 0.044) with the flash leading. Amblyopia is associated with the widening of the temporal binding window, specifically for fission when viewing binocularly with the beep leading. This suggests a developmental adaptation to delayed amblyopic eye visual processing to optimize audiovisual integration.

  15. An experimental test of two mathematical models applied to the size-weight illusion.

    Science.gov (United States)

    Sarris, V; Heineken, E

    1976-05-01

    Two quantitative models, which make different quantitative predictions for the amount of the size-weight illusion, were tested according to the psychophysical methods employed by the respective authors (magnitude estimation versus category ratings). Both models with their corresponding method were supported. This causes uncertainty over Anderson's chaim that the validity of both a model and the applied scale used is sufficiently test by the socalled joint testing procedure.

  16. The role of configurality in the Thatcher illusion: an ERP study.

    Science.gov (United States)

    Mestry, Natalie; Menneer, Tamaryn; Wenger, Michael J; Benikos, Nicholas; McCarthy, Rosaleen A; Donnelly, Nick

    2015-04-01

    The Thatcher illusion (Thompson in Perception, 9, 483-484, 1980) is often explained as resulting from recognising a distortion of configural information when 'Thatcherised' faces are upright but not when inverted. However, recent behavioural studies suggest that there is an absence of perceptual configurality in upright Thatcherised faces (Donnelly et al. in Attention, Perception & Psychophysics, 74, 1475-1487, 2012) and both perceptual and decisional sources of configurality in behavioural tasks with Thatcherised stimuli (Mestry, Menneer et al. in Frontiers in Psychology, 3, 456, 2012). To examine sources linked to the behavioural experience of the illusion, we studied inversion and Thatcherisation of faces (comparing across conditions in which no features, the eyes, the mouth, or both features were Thatcherised) on a set of event-related potential (ERP) components. Effects of inversion were found at the N170, P2 and P3b. Effects of eye condition were restricted to the N170 generated in the right hemisphere. Critically, an interaction of orientation and eye Thatcherisation was found for the P3b amplitude. Results from an individual with acquired prosopagnosia who can discriminate Thatcherised from typical faces but cannot categorise them or perceive the illusion (Mestry, Donnelly et al. in Neuropsychologia, 50, 3410-3418, 2012) only differed from typical participants at the P3b component. Findings suggest the P3b links most directly to the experience of the illusion. Overall, the study showed evidence consistent with both perceptual and decisional sources and the need to consider both in relation to configurality.

  17. The spinning dancer illusion and spontaneous brain fluctuations: an fMRI study.

    Science.gov (United States)

    Bernal, Byron; Guillen, Magno; Marquez, Juan Camilo

    2014-01-01

    The brain activation associated with the Spinning Dancer Illusion, a cognitive visual illusion, is not entirely known. Inferences from other study modalities point to the involvement of the dorso-parieto-occipital areas in the spontaneous switchings of perception in other bistable non-kinetic illusions. fMRI is a mature technique used to investigate the brain responses associated with mental changes. Resting-state fMRI is a novel technique that may help ascertain the effects of spontaneous brain changes in the top-down regulation of visual perception. The purpose of this report is to describe the brain activation associated with the subjective illusory changes of perception of a kinetic bistable stimulus. We hypothesize that there is a relationship between the perception phases with the very slow cortical spontaneous fluctuations, recently described. A single normal subject who was trained to produce voluntarily perception phase switches underwent a series of fMRI studies whose blocks were either defined post-hoc or accordingly with a predefined timeline to assess spontaneous and voluntarily evoked visual perception switches, respectively. Correlation of findings with resting-state fMRI and independent component analysis of the task series was sought. Phases of the rotation direction were found associated with right parietal activity. Independent component analysis of the task series and their comparison with basal resting-state components suggest that this activity is related to one of the very slow spontaneous brain fluctuations. The spontaneous fluctuations of the cortical activity may explain the subjective changes in perception of direction of the Spinning Dancer Illusion. This observation is a proof-of-principle, suggesting that the spontaneous brain oscillations may influence top-down sensory regulation.

  18. Directional organization and shape formation: new illusions and Helmholtz’s square

    OpenAIRE

    2015-01-01

    According to Helmholtz’s Square illusion, a square appears wider when it is filled with vertical lines and higher when filled with horizontal lines (Helmholtz, 1866). Recently, Pinna (2010a) demonstrat- ed that the grouping of small squares on the basis of the similarity principle influences also percep- tion of their shape and of the whole emerging shapes. The direction imparted by grouping is the main attribute that influences the shape by polarizing it in the same direction both globally a...

  19. The Rubber Hand Illusion: feeling of ownership and proprioceptive drift do not go hand in hand.

    Science.gov (United States)

    Rohde, Marieke; Di Luca, Massimiliano; Ernst, Marc O

    2011-01-01

    In the Rubber Hand Illusion, the feeling of ownership of a rubber hand displaced from a participant's real occluded hand is evoked by synchronously stroking both hands with paintbrushes. A change of perceived finger location towards the rubber hand (proprioceptive drift) has been reported to correlate with this illusion. To measure the time course of proprioceptive drift during the Rubber Hand Illusion, we regularly interrupted stroking (performed by robot arms) to measure perceived finger location. Measurements were made by projecting a probe dot into the field of view (using a semi-transparent mirror) and asking participants if the dot is to the left or to the right of their invisible hand (Experiment 1) or to adjust the position of the dot to that of their invisible hand (Experiment 2). We varied both the measurement frequency (every 10 s, 40 s, 120 s) and the mode of stroking (synchronous, asynchronous, just vision). Surprisingly, with frequent measurements, proprioceptive drift occurs not only in the synchronous stroking condition but also in the two control conditions (asynchronous stroking, just vision). Proprioceptive drift in the synchronous stroking condition is never higher than in the just vision condition. Only continuous exposure to asynchronous stroking prevents proprioceptive drift and thus replicates the differences in drift reported in the literature. By contrast, complementary subjective ratings (questionnaire) show that the feeling of ownership requires synchronous stroking and is not present in the asynchronous stroking condition. Thus, subjective ratings and drift are dissociated. We conclude that different mechanisms of multisensory integration are responsible for proprioceptive drift and the feeling of ownership. Proprioceptive drift relies on visuoproprioceptive integration alone, a process that is inhibited by asynchronous stroking, the most common control condition in Rubber Hand Illusion experiments. This dissociation implies that

  20. The Rubber Hand Illusion: feeling of ownership and proprioceptive drift do not go hand in hand.

    Directory of Open Access Journals (Sweden)

    Marieke Rohde

    Full Text Available In the Rubber Hand Illusion, the feeling of ownership of a rubber hand displaced from a participant's real occluded hand is evoked by synchronously stroking both hands with paintbrushes. A change of perceived finger location towards the rubber hand (proprioceptive drift has been reported to correlate with this illusion. To measure the time course of proprioceptive drift during the Rubber Hand Illusion, we regularly interrupted stroking (performed by robot arms to measure perceived finger location. Measurements were made by projecting a probe dot into the field of view (using a semi-transparent mirror and asking participants if the dot is to the left or to the right of their invisible hand (Experiment 1 or to adjust the position of the dot to that of their invisible hand (Experiment 2. We varied both the measurement frequency (every 10 s, 40 s, 120 s and the mode of stroking (synchronous, asynchronous, just vision. Surprisingly, with frequent measurements, proprioceptive drift occurs not only in the synchronous stroking condition but also in the two control conditions (asynchronous stroking, just vision. Proprioceptive drift in the synchronous stroking condition is never higher than in the just vision condition. Only continuous exposure to asynchronous stroking prevents proprioceptive drift and thus replicates the differences in drift reported in the literature. By contrast, complementary subjective ratings (questionnaire show that the feeling of ownership requires synchronous stroking and is not present in the asynchronous stroking condition. Thus, subjective ratings and drift are dissociated. We conclude that different mechanisms of multisensory integration are responsible for proprioceptive drift and the feeling of ownership. Proprioceptive drift relies on visuoproprioceptive integration alone, a process that is inhibited by asynchronous stroking, the most common control condition in Rubber Hand Illusion experiments. This dissociation implies

  1. An auditory illusion of infinite tempo change based on multiple temporal levels.

    Directory of Open Access Journals (Sweden)

    Guy Madison

    Full Text Available Humans and a few select insect and reptile species synchronise inter-individual behaviour without any time lag by predicting the time of future events rather than reacting to them. This is evident in music performance, dance, and drill. Although repetition of equal time intervals (i.e. isochrony is the central principle for such prediction, this simple information is used in a flexible and complex way that accommodates both multiples, subdivisions, and gradual changes of intervals. The scope of this flexibility remains largely uncharted, and the underlying mechanisms are a matter for speculation. Here I report an auditory illusion that highlights some aspects of this behaviour and that provides a powerful tool for its future study. A sound pattern is described that affords multiple alternative and concurrent rates of recurrence (temporal levels. An algorithm that systematically controls time intervals and the relative loudness among these levels creates an illusion that the perceived rate speeds up or slows down infinitely. Human participants synchronised hand movements with their perceived rate of events, and exhibited a change in their movement rate that was several times larger than the physical change in the sound pattern. The illusion demonstrates the duality between the external signal and the internal predictive process, such that people's tendency to follow their own subjective pulse overrides the overall properties of the stimulus pattern. Furthermore, accurate synchronisation with sounds separated by more than 8 s demonstrate that multiple temporal levels are employed for facilitating temporal organisation and integration by the human brain. A number of applications of the illusion and the stimulus pattern are suggested.

  2. Electrical Brain Responses to an Auditory Illusion and the Impact of Musical Expertise

    OpenAIRE

    Ioannaou, Christos I; Pereda, Ernesto; Lindsen, Job P.; Bhattacharya, Joydeep

    2015-01-01

    The presentation of two sinusoidal tones, one to each ear, with a slight frequency mismatch yields an auditory illusion of a beating frequency equal to the frequency difference between the two tones; this is known as binaural beat (BB). The effect of brief BB stimulation on scalp EEG is not conclusively demonstrated. Further, no studies have examined the impact of musical training associated with BB stimulation, yet musicians' brains are often associated with enhanced auditory processing. In ...

  3. The Closing of the Gender Gap as a Roy Model Illusion

    OpenAIRE

    Casey B. Mulligan; Yona Rubinstein

    2004-01-01

    Rising wage inequality within-gender since 1975 has created the illusion of rising wage equality between genders. In the 1970's, women were relatively equal (to each other) in terms of their earnings potential, so that nonwage factors may have dominated female labor supply decisions and nonworking women actually had more earnings potential than working women. By 1990, wages had become unequal enough that they dominated nonwage factors, so that nonworking women tended to be the ones with less ...

  4. Optical illusion alters M1 excitability after mirror therapy: a TMS study.

    Science.gov (United States)

    Läppchen, C H; Ringer, T; Blessin, J; Seidel, G; Grieshammer, S; Lange, R; Hamzei, F

    2012-11-01

    The contralesional primary motor cortex (M1) has been suggested to be involved in the motor recovery after mirror therapy, but whether the ipsilesional M1 is influenced by the contralesional M1 via transcallosal interhemispheric inhibition (IHI) is still unclear. The present study investigated the change of IHI as well as the intracortical inhibition and intracortical facilitation of both M1 induced by training in a mirror with the use of transcranial magnetic stimulation (TMS). In this 2 × 2 factorial design (time × group), healthy subjects exercised standardized motor skills with their right hand on four consecutive days. Either a mirror (mirror group) or a board (control group) was positioned between their hands. Before and after training TMS was applied along with training tests of both hands. Tests were the same motor skills exercised daily by both groups. Tests of the untrained left hand improved significantly more in the mirror group than in the control group after training (P = 0.02) and showed a close correlation with an increase of intracortical inhibition of M1(left). IHI did not show any difference between investigation time points and groups. The present study confirms the previous suggestion of the involvement of the "contralesional" left-side (ipsilateral to the hand behind the mirror) M1 after mirror therapy, which is not mediated by IHI. Even with the same motor skill training (both groups performed same motor skills) but with different visual information, different networks are involved in training-induced plasticity.

  5. 视错觉与建筑设计%Optical illusion and architectural design

    Institute of Scientific and Technical Information of China (English)

    张彧辉; 任晓峰

    2002-01-01

    视错觉普遍存在,不当的视错觉会干扰人对建筑物尺度、形状和深度的认识.如何避免视错觉和如何利用视错觉,在建筑设计上有十分重要的意义和价值.与建筑设计相关的形象错觉的种类有多种多样,应具体区分并恰当利用,利用得好可以弄拙成巧,反之,则弄巧成拙.

  6. "Soft-Engineering" Students Learning Math during Project Work on Optical Illusions

    DEFF Research Database (Denmark)

    Timcenko, Olga; Triantafyllou, Evangelia

    2015-01-01

    Media Technology is a study line between engineering, art and humanities, situated at Faculty of Engineering and Science of Aalborg University. Although formally students of engineering, Media Technology students show even greater difficulties with entry-level mathematical knowledge than typical ...

  7. The mirror illusion: does proprioceptive drift go hand in hand with sense of agency?

    Directory of Open Access Journals (Sweden)

    Daisuke eTAJIMA

    2015-02-01

    Full Text Available Vection can be regarded as the illusion of ‘whole-body’ position perception. In contrast, the mirror illusion is that of ‘body-part’ position perception. When participants viewed their left hands in a mirror positioned along the midsaggital axis while moving both hands synchronously, they hardly noticed the spatial offset between the hand in the mirror and the obscured real right hand. This illusion encompasses two phenomena: proprioceptive drift and sense of agency. Proprioceptive drift represented a perceptual change in the position of the obscured hand relative to that of the hand in the mirror. Sense of agency referred to the participants’ subjective sense of controlling body image as they would their own bodies. We examined the spatial offset between these two phenomena. Participants responded to a two-alternative forced choice (2AFC question regarding the subjective position of their right hands and questionnaires regarding sense of agency at various positions of the right hand. We analysed the 2AFC data using a support vector machine and compared its classification result and the questionnaire results. Our data analysis suggested that the two phenomena were observed in concentric space, but the estimated range of the proprioceptive drift was slightly narrower than the range of agency. Although this outcome can be attributed to differences in measurement or analysis, to our knowledge, this is the first report to suggest that proprioceptive drift and sense of agency are concentric and almost overlap.

  8. Neurophysiological Correlates of the Rubber Hand Illusion in Late Evoked and Alpha/Beta Band Activity

    Directory of Open Access Journals (Sweden)

    Isa S. Rao

    2017-07-01

    Full Text Available The rubber hand illusion (RHI allows insights into how the brain resolves conflicting multisensory information regarding body position and ownership. Previous neuroimaging studies have reported a variety of neurophysiological correlates of illusory hand ownership, with conflicting results likely originating from differences in experimental parameters and control conditions. Here, we overcome these limitations by using a fully automated and precisely-timed visuo-tactile stimulation setup to record evoked responses and oscillatory responses in participants who felt the RHI. Importantly, we relied on a combination of experimental conditions to rule out confounds of attention, body-stimulus position and stimulus duration and on the combination of two control conditions to identify neurophysiological correlates of illusory hand ownership. In two separate experiments we observed a consistent illusion-related attenuation of ERPs around 330 ms over frontocentral electrodes, as well as decreases of frontal alpha and beta power during the illusion that could not be attributed to changes in attention, body-stimulus position or stimulus duration. Our results reveal neural correlates of illusory hand ownership in late and likely higher-order rather than early sensory processes, and support a role of premotor and possibly intraparietal areas in mediating illusory body ownership.

  9. Directionally hiding objects and creating illusions above a carpet-like device by reflection holography

    Science.gov (United States)

    Cheng, Qiluan; Wu, Kedi; Shi, Yile; Wang, Hui; Wang, Guo Ping

    2015-02-01

    Realization of a perfect invisibility cloak still challenges the current fabricating technologies. Most experiments, if not all, are hence focused on carpet cloaks because of their relatively low requirements to material properties. Nevertheless, present invisibility carpets are used to hide beneath objects. Here, we report a carpet-like device to directionally conceal objects and further to create illusions above it. The device is fabricated through recording a reflection hologram of objects and is used to produce a time-reversed signal to compensate for the information of the objects and further to create light field of another object so as to realize both functions of hiding the objects and creating illusions, respectively. The carpet-like device can work for macroscopic objects at visible wavelength as the distance between objects and device is at decimeter scale. Our carpet-like device to realizing invisibility and creating illusions may provide a robust way for crucial applications of magic camouflaging and anti-detection etc.

  10. Neural representation of reward probability: evidence from the illusion of control.

    Science.gov (United States)

    Kool, Wouter; Getz, Sarah J; Botvinick, Matthew M

    2013-06-01

    To support reward-based decision-making, the brain must encode potential outcomes both in terms of their incentive value and their probability of occurrence. Recent research has made it clear that the brain bears multiple representations of reward magnitude, meaning that a single choice option may be represented differently-and even inconsistently-in different brain areas. There are some hints that the same may be true for reward probability. Preliminary evidence hints that, even as systematic distortions of probability are expressed in behavior, these may not always be uniformly reflected at the neural level: Some neural representations of probability may be immune from such distortions. This study provides new evidence consistent with this possibility. Participants in a behavioral experiment displayed a classic "illusion of control," providing higher estimates of reward probability for gambles they had chosen than for identical gambles that were imposed on them. However, an fMRI study of the same task revealed that neural prediction error signals, arising when gamble outcomes were revealed, were unaffected by the illusion of control. The resulting behavioral-neural dissociation reinforces the case for multiple, inconsistent internal representations of reward probability, while also prompting a reinterpretation of the illusion of control effect itself.

  11. Exploring the subjective experience of the “rubber hand” illusion

    Science.gov (United States)

    Valenzuela Moguillansky, Camila; O'Regan, J. Kevin; Petitmengin, Claire

    2013-01-01

    Despite the fact that the rubber hand illusion (RHI) is an experimental paradigm that has been widely used in the last 14 years to investigate different aspects of the sense of bodily self, very few studies have sought to investigate the subjective nature of the experience that the RHI evokes. The present study investigates the phenomenology of the RHI through a specific elicitation method. More particularly, this study aims at assessing whether the conditions usually used as control in the RHI have an impact in the sense of body ownership and at determining whether there are different stages in the emergence of the illusion. The results indicate that far from being “all or nothing,” the illusion induced by the RHI protocol involves nuances in the type of perceptual changes that it creates. These perceptual changes affect not only the participants' perception of the rubber hand but also the perception of their real hand. In addition, perceptual effects may vary greatly between participants and, importantly, they evolve over time. PMID:24167480

  12. The mirror illusion: does proprioceptive drift go hand in hand with sense of agency?

    Science.gov (United States)

    Tajima, Daisuke; Mizuno, Tota; Kume, Yuichiro; Yoshida, Takako

    2015-01-01

    Vection can be regarded as the illusion of "whole-body" position perception. In contrast, the mirror illusion is that of "body-part" position perception. When participants viewed their left hands in a mirror positioned along the midsaggital axis while moving both hands synchronously, they hardly noticed the spatial offset between the hand in the mirror and the obscured real right hand. This illusion encompasses two phenomena: proprioceptive drift and sense of agency. Proprioceptive drift represented a perceptual change in the position of the obscured hand relative to that of the hand in the mirror. Sense of agency referred to the participants' subjective sense of controlling body image as they would their own bodies. We examined the spatial offset between these two phenomena. Participants responded to a two-alternative forced choice (2AFC) question regarding the subjective position of their right hands and questionnaires regarding sense of agency at various positions of the right hand. We analyzed the 2AFC data using a support vector machine and compared its classification result and the questionnaire results. Our data analysis suggested that the two phenomena were observed in concentric space, but the estimated range of the proprioceptive drift was slightly narrower than the range of agency. Although this outcome can be attributed to differences in measurement or analysis, to our knowledge, this is the first report to suggest that proprioceptive drift and sense of agency are concentric and almost overlap.

  13. Neural Correlate of the Thatcher Face Illusion in a Monkey Face-Selective Patch.

    Science.gov (United States)

    Taubert, Jessica; Van Belle, Goedele; Vanduffel, Wim; Rossion, Bruno; Vogels, Rufin

    2015-07-01

    Compelling evidence that our sensitivity to facial structure is conserved across the primate order comes from studies of the "Thatcher face illusion": humans and monkeys notice changes in the orientation of facial features (e.g., the eyes) only when faces are upright, not when faces are upside down. Although it is presumed that face perception in primates depends on face-selective neurons in the inferior temporal (IT) cortex, it is not known whether these neurons respond differentially to upright faces with inverted features. Using microelectrodes guided by functional MRI mapping, we recorded cell responses in three regions of monkey IT cortex. We report an interaction in the middle lateral face patch (ML) between the global orientation of a face and the local orientation of its eyes, a response profile consistent with the perception of the Thatcher illusion. This increased sensitivity to eye orientation in upright faces resisted changes in screen location and was not found among face-selective neurons in other areas of IT cortex, including neurons in another face-selective region, the anterior lateral face patch. We conclude that the Thatcher face illusion is correlated with a pattern of activity in the ML that encodes faces according to a flexible holistic template.

  14. Speech and non-speech audio-visual illusions: a developmental study.

    Directory of Open Access Journals (Sweden)

    Corinne Tremblay

    Full Text Available It is well known that simultaneous presentation of incongruent audio and visual stimuli can lead to illusory percepts. Recent data suggest that distinct processes underlie non-specific intersensory speech as opposed to non-speech perception. However, the development of both speech and non-speech intersensory perception across childhood and adolescence remains poorly defined. Thirty-eight observers aged 5 to 19 were tested on the McGurk effect (an audio-visual illusion involving speech, the Illusory Flash effect and the Fusion effect (two audio-visual illusions not involving speech to investigate the development of audio-visual interactions and contrast speech vs. non-speech developmental patterns. Whereas the strength of audio-visual speech illusions varied as a direct function of maturational level, performance on non-speech illusory tasks appeared to be homogeneous across all ages. These data support the existence of independent maturational processes underlying speech and non-speech audio-visual illusory effects.

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

    Science.gov (United States)

    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.

  16. Visuo-haptic interactions in unilateral spatial neglect: the crossmodal Judd illusion

    Directory of Open Access Journals (Sweden)

    Flavia eMancini

    2011-11-01

    Full Text Available Unilateral spatial neglect has been mainly investigated in the visual modality; only a few studies compared spatial neglect in different sensory modalities, and explored their multisensory interactions, with controversial results. We investigated the integration between vision and haptics, through a bisection task of a crossmodal length illusion, the Judd variant of the Müller-Lyer illusion. We examined right-brain-damaged patients with (n=7 and without (n=7 left unilateral spatial neglect, and neurologically unimpaired participants (n=14 in the bisection of Judd stimuli under visual, haptic, and visuo-haptic presentation. Neglect patients showed the characteristic rightward bias in the bisection of a baseline stimulus in the visual modality, but not in the haptic and visuo-haptic conditions. The illusory effects were preserved in each group and in each modality, indicating that the processing of the length illusion is independent of the presence of deficits of spatial attention and representation. Spatial neglect can be modality-specific, but visual and tactile sensory inputs are properly integrated.

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

    Science.gov (United States)

    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.

  18. Perceiving and acting upon weight illusions in the absence of somatosensory information.

    Science.gov (United States)

    Buckingham, Gavin; Michelakakis, Elizabeth Evgenia; Cole, Jonathan

    2016-04-01

    When lifting novel objects, individuals' fingertip forces are influenced by a variety of cues such as volume and apparent material. This means that heavy-looking objects tend to be lifted with more force than lighter-looking objects, even when they weigh the same amount as one another. Expectations about object weight based on visual appearance also influence how heavy an object feels when it is lifted. For instance, in the "size-weight illusion," small objects feel heavier than equally weighted large objects. Similarly, in the "material-weight illusion," objects that seem to be made from light-looking materials feel heavier than objects of the same weight that appear to be made from heavy-looking materials. In this study, we investigated these perceptual and sensorimotor effects in IW, an individual with peripheral deafferentation (i.e., a loss of tactile and proprioception feedback). We examined his perceptions of heaviness and fingertip force application over repeated lifts of objects that varied in size or material properties. Despite being able to report real weight differences, IW did not appear to experience the size- or material-weight illusions. Furthermore, he showed no evidence of sensorimotor prediction based on size and material cues. The results are discussed in the context of forward models and their possible influence on weight perception and fingertip force control.

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

    Directory of Open Access Journals (Sweden)

    Zane Z Zheng

    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.

  20. Illusion of agency in patients with Gilles de la Tourette Syndrome.

    Science.gov (United States)

    Delorme, Cécile; Salvador, Alexandre; Voon, Valerie; Roze, Emmanuel; Vidailhet, Marie; Hartmann, Andreas; Worbe, Yulia

    2016-04-01

    The sense of agency refers to the conscious experience of authorship and control over actions. The voluntary or involuntary nature of tics, which are the hallmark of Gilles de la Tourette Syndrome (GTS), is unclear. Here, we studied metacognitive processing of agency in an explicit agency task on non-medicated and medicated GTS patients compared to matched controls. In this task, the participants made judgements of control and performance after completion of a computerized game where they had to catch targets with a cursor by moving the computer mouse. The task included several conditions, where the objective control over the cursor could be normal, disrupted or artificially enhanced. We show that GTS patients, independently of medication status, based their judgments of agency predominantly on the matching between their intention and the outcome, i.e., had an illusion of agency in the task condition where their performance was artificially enhanced. Nevertheless, they recognized not to be fully in control in conditions of disrupted control. The propensity to illusions of agency was negatively correlated with global disease severity. Our findings suggest alterations of metacognition of agency in GTS patients. This illusion of agency could reflect a compensatory mechanism related to tic control, but is more likely to be related to deviant brain maturation in GTS.

  1. The Content of Imagined Sounds Changes Visual Motion Perception in the Cross-Bounce Illusion

    Science.gov (United States)

    Berger, Christopher C.; Ehrsson, H. Henrik

    2017-01-01

    Can what we imagine hearing change what we see? Whether imagined sensory stimuli are integrated with external sensory stimuli to shape our perception of the world has only recently begun to come under scrutiny. Here, we made use of the cross-bounce illusion in which an auditory stimulus presented at the moment two passing objects meet promotes the perception that the objects bounce off rather than cross by one another to examine whether the content of imagined sound changes visual motion perception in a manner that is consistent with multisensory integration. The results from this study revealed that auditory imagery of a sound with acoustic properties typical of a collision (i.e., damped sound) promoted the bounce-percept, but auditory imagery of the same sound played backwards (i.e., ramped sound) did not. Moreover, the vividness of the participants’ auditory imagery predicted the strength of this imagery-induced illusion. In a separate experiment, we ruled out the possibility that changes in attention (i.e., sensitivity index d′) or response bias (response bias index c) were sufficient to explain this effect. Together, these findings suggest that this imagery-induced multisensory illusion reflects the successful integration of real and imagined cross-modal sensory stimuli, and more generally, that what we imagine hearing can change what we see. PMID:28071707

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

    Directory of Open Access Journals (Sweden)

    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'.

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

    Science.gov (United States)

    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.

  4. Pronunciation difficulty, temporal regularity, and the speech-to-song illusion.

    Science.gov (United States)

    Margulis, Elizabeth H; Simchy-Gross, Rhimmon; Black, Justin L

    2015-01-01

    The speech-to-song illusion (Deutsch et al., 2011) tracks the perceptual transformation from speech to song across repetitions of a brief spoken utterance. Because it involves no change in the stimulus itself, but a dramatic change in its perceived affiliation to speech or to music, it presents a unique opportunity to comparatively investigate the processing of language and music. In this study, native English-speaking participants were presented with brief spoken utterances that were subsequently repeated ten times. The utterances were drawn either from languages that are relatively difficult for a native English speaker to pronounce, or languages that are relatively easy for a native English speaker to pronounce. Moreover, the repetition could occur at regular or irregular temporal intervals. Participants rated the utterances before and after the repetitions on a 5-point Likert-like scale ranging from "sounds exactly like speech" to "sounds exactly like singing." The difference in ratings before and after was taken as a measure of the strength of the speech-to-song illusion in each case. The speech-to-song illusion occurred regardless of whether the repetitions were spaced at regular temporal intervals or not; however, it occurred more readily if the utterance was spoken in a language difficult for a native English speaker to pronounce. Speech circuitry seemed more liable to capture native and easy-to-pronounce languages, and more reluctant to relinquish them to perceived song across repetitions.

  5. 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.

  6. The Literature Review of Money Illusion%货币错觉研究文献综述

    Institute of Scientific and Technical Information of China (English)

    陈亮; 顾乃康

    2016-01-01

    货币错觉是指人们在考虑经济决策的时候,仅仅关注货币名义上的价值,而不去理会货币的实际购买力的一种心理错觉,是货币政策的通货膨胀效应。本文从货币错觉的内涵、对货币错觉理论的认知以及货币错觉实证研究进展三个方面对货币错觉的国内外相关文献进行了较为全面的梳理,并给出了一个文献研究的评述,目的是为基于货币错觉的行为金融理论与实证研究指明方向。%Money illusion refers to people in economic decision -making when considering only the nominal value of the currency concerned , and not to ignore the currency of a psychological illusion of real purchasing power , inflation effects of monetary policy. Based on the nature of the money illusion , money illusion theory and monetary cognitive illusion Empirical Studies of three aspects of the money illusion of relevant literature for a more comprehensive analysis and gives a literature reviewed , with the aim give directions for the conduct of financial theory and empirical research on money illusion.

  7. Aristotle's illusion reveals interdigit functional somatosensory alterations in focal hand dystonia.

    Science.gov (United States)

    Tinazzi, Michele; Marotta, Angela; Fasano, Alfonso; Bove, Francesco; Bentivoglio, Anna Rita; Squintani, Giovanna; Pozzer, Lara; Fiorio, Mirta

    2013-03-01

    In focal hand dystonia, the cortical somatosensory representation of the fingers is abnormal, with overlapping receptive fields and reduced interdigit separation. These abnormalities are associated with deficits in sensory perception, as previously demonstrated by applying tactile stimuli to one finger at a time. What is still unknown is whether the sensory deficits can be observed when tactile perception involves more than one finger. To address this issue, we applied 'Aristotle's illusion' to 15 patients with focal hand dystonia, 15 patients with dystonia not affecting the hand (blepharospasm and cervical dystonia) and 15 healthy control subjects. In this illusion, one object touching the contact point of two crossed fingertips is perceived as two objects by a blindfolded subject. The same object placed between two parallel fingertips is correctly perceived as one. The illusory doubling sensation is because of the fact that the contact point between the crossed fingers consists of non-adjacent and functionally unrelated skin regions, which usually send sensory signals to separate spots in the somatosensory cortex. In our study, participants were touched by one sphere between the second-third digits, the second-fourth digits and the fourth-fifth digits of both hands, either in crossed or in parallel position, and had to refer whether they felt one or two stimuli. The percentage of 'two stimuli' responses was an index of the illusory doubling. Both healthy control subjects and dystonic patients presented Aristotle's illusion when the fingers were crossed. However, patients with focal hand dystonia presented a significant reduction of the illusion when the sphere was placed between the crossed fourth and fifth digits of the affected hand. This reduction correlated with the severity of motor disease at the fingers. Similar findings were not observed in non-hand dystonia and control groups. The reduction of Aristotle's illusion in non-affected fingers and its

  8. 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.

  9. Ageing and the Moses illusion: older adults fall for Moses but if asked directly, stick with Noah.

    Science.gov (United States)

    Umanath, Sharda; Dolan, Patrick O; Marsh, Elizabeth J

    2014-01-01

    Many people respond "two" to the question "How many animals of each kind did Moses take on the ark?", even though they know the reference should be to Noah. The Moses Illusion demonstrates a failure to apply stored knowledge (Erickson & Mattson, 1981). Of interest was whether older adults' robust knowledge bases would protect them from vulnerability to this illusion. Of secondary interest were any age differences in the memorial consequences of the illusion, and whether older adults' prior knowledge would protect them from later reproducing information from distorted questions (e.g., later saying that Moses took two animals of each kind on the ark). Surprisingly, older adults fell for the Moses Illusion more often than did younger adults. However, falling for the illusion did not affect older adults' later memory; they were less suggestible than young adults. Most importantly, older adults were more likely to recover from exposure to distorted questions and respond correctly. Explanations of these findings, drawing on theories of cognitive ageing, are discussed.

  10. 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.

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

    Science.gov (United States)

    Lee, Hye Jin; Lee, Jaedong; Kim, Chi Jung; Kim, Gerard J.; Kim, Eun-Soo; Whang, Mincheol

    2015-01-01

    “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). PMID:25835301

  12. 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.

  13. 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.

  14. My Body Had a Mind of Its Own: On Teaching, the Illusion of Control, and the Terrifying Limits of Governmentality (Part I)

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    Koza, Julia Eklund

    2009-01-01

    This essay examines control discourse in and out of educational settings, arguing that illusions of control are among the means by which governance is accomplished in domains far from schools. The tactical productivity of such illusions in non-school settings "necessitates" and explicates their prevalence in education. The first installment of…

  15. How visual illusions illuminate complementary brain processes: illusory depth from brightness and apparent motion of illusory contours.

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    Grossberg, Stephen

    2014-01-01

    Neural models of perception clarify how visual illusions arise from adaptive neural processes. Illusions also provide important insights into how adaptive neural processes work. This article focuses on two illusions that illustrate a fundamental property of global brain organization; namely, that advanced brains are organized into parallel cortical processing streams with computationally complementary properties. That is, in order to process certain combinations of properties, each cortical stream cannot process complementary properties. Interactions between these streams, across multiple processing stages, overcome their complementary deficiencies to compute effective representations of the world, and to thereby achieve the property of complementary consistency. The two illusions concern how illusory depth can vary with brightness, and how apparent motion of illusory contours can occur. Illusory depth from brightness arises from the complementary properties of boundary and surface processes, notably boundary completion and surface-filling in, within the parvocellular form processing cortical stream. This illusion depends upon how surface contour signals from the V2 thin stripes to the V2 interstripes ensure complementary consistency of a unified boundary/surface percept. Apparent motion of illusory contours arises from the complementary properties of form and motion processes across the parvocellular and magnocellular cortical processing streams. This illusion depends upon how illusory contours help to complete boundary representations for object recognition, how apparent motion signals can help to form continuous trajectories for target tracking and prediction, and how formotion interactions from V2-to-MT enable completed object representations to be continuously tracked even when they move behind intermittently occluding objects through time.

  16. Body ownership and experiential ownership in the self-touching illusion

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    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.

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

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    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

  18. Size-weight illusion and anticipatory grip force scaling following unilateral cortical brain lesion.

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    Li, Yong; Randerath, Jennifer; Goldenberg, Georg; Hermsdörfer, Joachim

    2011-04-01

    The prediction of object weight from its size is an important prerequisite of skillful object manipulation. Grip and load forces anticipate object size during early phases of lifting an object. A mismatch between predicted and actual weight when two different sized objects have the same weight results in the size-weight illusion (SWI), the small object feeling heavier. This study explores whether lateralized brain lesions in patients with or without apraxia alter the size-weight illusion and impair anticipatory finger force scaling. Twenty patients with left brain damage (LBD, 10 with apraxia, 10 without apraxia), ten patients with right brain damage (RBD), and matched control subjects lifted two different-sized boxes in alternation. All subjects experienced a similar size-weight illusion. The anticipatory force scaling of all groups was in correspondence with the size cue: higher forces and force rates were applied to the big box and lower forces and force rates to the small box during the first lifts. Within few lifts, forces were scaled to actual object weight. Despite the lack of significant differences at group level, 5 out of 20 LBD patients showed abnormal predictive scaling of grip forces. They differed from the LBD patients with normal predictive scaling by a greater incidence of posterior occipito-parietal lesions but not by a greater incidence of apraxia. The findings do not support a more general role for the motor-dominant left hemisphere, or an influence of apraxia per se, in the scaling of finger force according to object properties. However, damage in the vicinity of the parietal-occipital junction may be critical for deriving predictions of weight from size.

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

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    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.

  20. The effect of the Ebbinghaus illusion on grasping behaviour of children.

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    Hanisch, C; Konczak, J; Dohle, C

    2001-03-01

    Within the context of the Ebbinghaus illusion, adults regularly misjudge the physical size of a centre disc, yet scale their hand aperture according to its actual size. Separate visual pathways for perception and action are assumed to account for this finding. The dorsal visual stream is said to elaborate on egocentric (visuomotor), while the ventral stream is involved in allocentric transformations (object recognition). This study examines the ontogenetic development of this dissociation between perception and action in 35 children between the ages of 5 and 12 years. We report four major results. First, when children judged object size without grasping the disc, their judgements were deceived by the illusion to the same extent as adults. However, when asked to estimate size and then to grasp the disc, young children's (5-7 years) perceptual judgements became unreliable, while adults were still reliably deceived by the illusion in 80% of their trials. Second, the younger the children, the more their aperture was affected by the illusional surround. Discs of the same size were grasped with a smaller aperture when surrounded by a small annulus, although they were perceived as being larger. Third, young children used the largest safety margin during grasping. Fourth, the reliance on visual feedback decreased with increasing age, which was documented by shorter movement times and earlier maximum hand opening during grasping in the older children (feedforward control). Our results indicate that grasping behaviour in children is subject to an interaction between ventral and dorsal processes. Both pathways seem not to be functionally segregated in early and middle childhood. The data are inconclusive about whether young children predominantly use a specific visual stream for either a perceptual or motor task. However, our data demonstrate that children were relying on both visual processing streams during perceptual as well as visuomotor tasks. We found that children used

  1. Audition influences color processing in the sound-induced visual flash illusion.

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    Mishra, Jyoti; Martinez, Antigona; Hillyard, Steven A

    2013-12-18

    Multisensory interactions can lead to illusory percepts, as exemplified by the sound-induced extra flash illusion (SIFI: Shams, Kamitani, & Shimojo, 2000, 2002). In this illusion, an audio-visual stimulus sequence consisting of two pulsed sounds and a light flash presented within a 100 ms time window generates the visual percept of two flashes. Here, we used colored visual stimuli to investigate whether concurrent auditory stimuli can affect the perceived features of the illusory flash. Zero, one or two pulsed sounds were presented concurrently with either a red or green flash or with two flashes of different colors (red followed by green) in rapid sequence. By querying both the number and color of the participants' visual percepts, we found that the double flash illusion is stimulus specific: i.e., two sounds paired with one red or one green flash generated the percept of two red or two green flashes, respectively. This implies that the illusory second flash is induced at a level of visual processing after perceived color has been encoded. In addition, we found that the presence of two sounds influenced the integration of color information from two successive flashes. In the absence of any sounds, a red and a green flash presented in rapid succession fused to form a single orange percept, but when accompanied by two sounds, this integrated orange percept was perceived to flash twice on a significant proportion of trials. In addition, the number of concurrent auditory stimuli modified the degree to which the successive flashes were integrated to an orange percept vs. maintained as separate red-green percepts. Overall, these findings show that concurrent auditory input can affect both the temporal and featural properties of visual percepts. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. 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

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

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    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.

  4. Women in Illusion:An Analysis of Women Characters in The Glass Menagerie

    Institute of Scientific and Technical Information of China (English)

    王冬梅

    2009-01-01

    The paper tries to analyze women characters in Tennessee Williams' Drama The Glass Menagerie.Laura and Amanda,the daughter and the mother,represent the delicate and fragile southern female images.They both feel desper-ate about the reality and retreat to their own world of illusions.Laura,because of her crippled body,cannot face the or-dinary problems of life and withdraws into the world of glass animals.Amanda Wingfield is unable to face the harsh struggle for survival,constantly retreats to her past memories.

  5. Visual illusions and ethnocentrism: exemplars for teaching cross-cultural concepts.

    Science.gov (United States)

    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.

  6. [What am I and (which are) the illusions of my self consciousness?].

    Science.gov (United States)

    Agrest, Martín

    2008-01-01

    Departing from Daniel Dennett's and Douglas Hofstadter's ideas, the present paper explores what the self and consciousness are and puts forward a possible explanation of their relationship with the brain. The paper deconstructs the illusions of my self and those of my consciousness, how they are produced and which the key elements to understand our reluctance to see ourselves as brains are. The self is considered a powerful myth but, at the same time, from a functionalist perspective, also an indispensable device in our daily life and in our explanations about others and about ourselves.

  7. The illusion of presence influences VR distraction: effects on cold-pressor pain.

    Science.gov (United States)

    Gutierrez-Martinez, Olga; Gutierrez-Maldonado, Jose; Cabas-Hoyos, Kattia; Loreto, Desirée

    2010-01-01

    This study investigated whether VR presence influences how effectively VR distraction reduces pain intensity during a cold-pressor experience. Thirty-seven healthy students underwent a cold pressor task while interacting with a VR distraction world. After the VR cold-pressor experience, each subject provided VAS ratings of the most intense pain experienced during the hand immersion and rated their illusion of having been inside the virtual world. Results showed that the amount of VR presence reported correlated significantly and negatively with ratings of pain intensity. The importance of using an appropriately designed VR to achieve effective VR analgesia is highlighted.

  8. Multisensory stimulation can induce an illusion of larger belly size in immersive virtual reality.

    Directory of Open Access Journals (Sweden)

    Jean-Marie Normand

    Full Text Available BACKGROUND: Body change illusions have been of great interest in recent years for the understanding of how the brain represents the body. Appropriate multisensory stimulation can induce an illusion of ownership over a rubber or virtual arm, simple types of out-of-the-body experiences, and even ownership with respect to an alternate whole body. Here we use immersive virtual reality to investigate whether the illusion of a dramatic increase in belly size can be induced in males through (a first person perspective position (b synchronous visual-motor correlation between real and virtual arm movements, and (c self-induced synchronous visual-tactile stimulation in the stomach area. METHODOLOGY: Twenty two participants entered into a virtual reality (VR delivered through a stereo head-tracked wide field-of-view head-mounted display. They saw from a first person perspective a virtual body substituting their own that had an inflated belly. For four minutes they repeatedly prodded their real belly with a rod that had a virtual counterpart that they saw in the VR. There was a synchronous condition where their prodding movements were synchronous with what they felt and saw and an asynchronous condition where this was not the case. The experiment was repeated twice for each participant in counter-balanced order. Responses were measured by questionnaire, and also a comparison of before and after self-estimates of belly size produced by direct visual manipulation of the virtual body seen from the first person perspective. CONCLUSIONS: The results show that first person perspective of a virtual body that substitutes for the own body in virtual reality, together with synchronous multisensory stimulation can temporarily produce changes in body representation towards the larger belly size. This was demonstrated by (a questionnaire results, (b the difference between the self-estimated belly size, judged from a first person perspective, after and before the

  9. Two Left Hands, Ten Interlaced Fingers: A New Rubber Hand Illusion.

    Science.gov (United States)

    White, Rebekah C; Bowen, Dillon; Dumbalska, Tsvetomira; Hoeger, Katharine; Mok, Anastasia Y S

    2016-03-01

    A variation on the rubber hand paradigm elicits an illusion in which the participant's sense of body ownership can switch back and forth between two viewed prosthetic hands. The interlaced fingers paradigm involves three prosthetic left hands: Two are positioned in full view of the participant, with their fingers interlaced, and the fingers of a third prosthetic hand are interlaced with the fingers of the participant's left hand, which is hidden from view. The examiner alternates brushstrokes to the two viewed prosthetic hands, while administering synchronous brushstrokes to the participant's hidden hand. Most participants experience ownership for the prosthetic hand that is being stroked at a given moment.

  10. Manchester's Magiscope: An Interesting Optics Puzzle

    Science.gov (United States)

    Lancor, Rachael; Lancor, Brian

    2017-02-01

    The Magiscope was an attraction at Manchester's department store in Madison, WI, in 1939 that allowed children to peek into Santa's workshop (as shown in Fig. 1). The "magiscope" was a telescope-like device that gave children the illusion they were looking at a distant Santa, when in fact they were looking at a fabricated workshop on an upper level of the department store. In this article, we describe how we used the puzzle of the magiscope as a final assessment for our optics unit in an introductory physics course.

  11. Influence of rhythmic grouping on duration perception: a novel auditory illusion.

    Directory of Open Access Journals (Sweden)

    Eveline Geiser

    Full Text Available This study investigated a potential auditory illusion in duration perception induced by rhythmic temporal contexts. Listeners with or without musical training performed a duration discrimination task for a silent period in a rhythmic auditory sequence. The critical temporal interval was presented either within a perceptual group or between two perceptual groups. We report the just-noticeable difference (difference limen, DL for temporal intervals and the point of subjective equality (PSE derived from individual psychometric functions based on performance of a two-alternative forced choice task. In musically untrained individuals, equal temporal intervals were perceived as significantly longer when presented between perceptual groups than within a perceptual group (109.25% versus 102.5% of the standard duration. Only the perceived duration of the between-group interval was significantly longer than its objective duration. Musically trained individuals did not show this effect. However, in both musically trained and untrained individuals, the relative difference limens for discriminating the comparison interval from the standard interval were larger in the between-groups condition than in the within-group condition (7.3% vs. 5.6% of the standard duration. Thus, rhythmic grouping affected sensitivity to duration changes in all listeners, with duration differences being harder to detect at boundaries of rhythm groups than within rhythm groups. Our results show for the first time that temporal Gestalt induces auditory duration illusions in typical listeners, but that musical experts are not susceptible to this effect of rhythmic grouping.

  12. Influence of rhythmic grouping on duration perception: a novel auditory illusion.

    Science.gov (United States)

    Geiser, Eveline; Gabrieli, John D E

    2013-01-01

    This study investigated a potential auditory illusion in duration perception induced by rhythmic temporal contexts. Listeners with or without musical training performed a duration discrimination task for a silent period in a rhythmic auditory sequence. The critical temporal interval was presented either within a perceptual group or between two perceptual groups. We report the just-noticeable difference (difference limen, DL) for temporal intervals and the point of subjective equality (PSE) derived from individual psychometric functions based on performance of a two-alternative forced choice task. In musically untrained individuals, equal temporal intervals were perceived as significantly longer when presented between perceptual groups than within a perceptual group (109.25% versus 102.5% of the standard duration). Only the perceived duration of the between-group interval was significantly longer than its objective duration. Musically trained individuals did not show this effect. However, in both musically trained and untrained individuals, the relative difference limens for discriminating the comparison interval from the standard interval were larger in the between-groups condition than in the within-group condition (7.3% vs. 5.6% of the standard duration). Thus, rhythmic grouping affected sensitivity to duration changes in all listeners, with duration differences being harder to detect at boundaries of rhythm groups than within rhythm groups. Our results show for the first time that temporal Gestalt induces auditory duration illusions in typical listeners, but that musical experts are not susceptible to this effect of rhythmic grouping.

  13. 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.

  14. Reporting a Remarkable Visual Illusion Due to Temporal Lobe Epilepsy and an Unusual Response to Lamotrigine

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    Mostafavi

    2016-01-01

    Full Text Available Introduction Visual illusions and hallucinations may accompany a wide variety of disorders with many various etiologies; therefore, they are nonspecific phenomena. In a partial seizure, a localized hyper synchronous neuronal discharge evolving into a partial seizure affecting a particular cortical region or cerebral subsystem can give rise to psychotic symptoms like visual hallucination. This case study introduces a patient with metamorphopsia, a rare visual illusion, that was treated with lamotrigine. Case Presentation This case study introduces a 34-year-old man with a history of falling. After a while, his seizures became accompanied with aura and, during the attack, he saw people and objects as bloody. He was asymptomatic between the attacks, with no visceral feeling and with dysphoric mood and borderline IQ. He was resistant to various treatments. After 6 months administration of lamotrigine, he has not had any seizure attacks and the psychotic symptoms have improved. Conclusions The psychotic symptoms due to temporal lobe epilepsy can be resolved with lamotrigine administration.

  15. The Thatcher illusion reveals orientation dependence in brain regions involved in processing facial expressions.

    Science.gov (United States)

    Psalta, Lilia; Young, Andrew W; Thompson, Peter; Andrews, Timothy J

    2014-01-01

    Although the processing of facial identity is known to be sensitive to the orientation of the face, it is less clear whether orientation sensitivity extends to the processing of facial expressions. To address this issue, we used functional MRI (fMRI) to measure the neural response to the Thatcher illusion. This illusion involves a local inversion of the eyes and mouth in a smiling face-when the face is upright, the inverted features make it appear grotesque, but when the face is inverted, the inversion is no longer apparent. Using an fMRI-adaptation paradigm, we found a release from adaptation in the superior temporal sulcus-a region directly linked to the processing of facial expressions-when the images were upright and they changed from a normal to a Thatcherized configuration. However, this release from adaptation was not evident when the faces were inverted. These results show that regions involved in processing facial expressions display a pronounced orientation sensitivity.

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

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    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.

  17. The illusion of nonmediation in telecommunication: voice intensity biases distance judgments to a communication partner.

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    Zhang, Chao; Lakens, Daniël; IJsselsteijn, Wijnand A

    2015-05-01

    The illusion of nonmediation is an experience in mediated communication where individuals respond as if the medium is not there. It is frequently associated with advanced media technology, such as virtual environments and teleconference systems. In this paper, we investigate whether people experience an illusion of nonmediation during interactions as simple as making a phone call. In three experiments, participants were asked to listen to someone's voice on a mobile phone (Experiment 1) or through VoIP software (Experiment 2 and 3) before guessing the location of the person and indicating this location on a map. Results consistently demonstrated that louder voices were judged to be closer, as if the technical mediation was ignored. Combining the three experiments, a small-scale meta-analysis yielded an effect size estimate of d=0.37 for the 'louder-as-closer' effect. Implications of the results and suggestions for future research are discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Decreased Corticospinal Excitability after the Illusion of Missing Part of the Arm.

    Science.gov (United States)

    Kilteni, Konstantina; Grau-Sánchez, Jennifer; Veciana De Las Heras, Misericordia; Rodríguez-Fornells, Antoni; Slater, Mel

    2016-01-01

    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.

  19. 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.

  20. The human touch: skin temperature during the rubber hand illusion in manual and automated stroking procedures.

    Directory of Open Access Journals (Sweden)

    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.

  1. 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.

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

    Science.gov (United States)

    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.

  3. Erroneous gambling-related beliefs as illusions of primary and secondary control: a confirmatory factor analysis.

    Science.gov (United States)

    Ejova, Anastasia; Delfabbro, Paul H; Navarro, Daniel J

    2015-03-01

    Different classification systems for erroneous beliefs about gambling have been proposed, consistently alluding to 'illusion of control' and 'gambler's fallacy' categories. None of these classification systems have, however, considered the how the illusion of control and the gambler's fallacy might be interrelated. In this paper, we report the findings of a confirmatory factor analysis that examines the proposal that most erroneous gambling-related beliefs can be defined in terms of Rothbaum et al.'s (J Pers Soc Psychol, doi: 10.1037/0022-3514.42.1.5 , 1982) distinction between 'primary' and 'secondary' illusory control, with the former being driven to a large extent by the well-known gambler's fallacy and the latter being driven by a complex of beliefs about supernatural forces such as God and luck. A survey consisting of 100 items derived from existing instruments was administered to 329 participants. The analysis confirmed the existence of two latent structures (beliefs in primary and secondary control), while also offering support to the idea that gambler's fallacy-style reasoning may underlie both perceived primary control and beliefs about the cyclical nature of luck, a form of perceived secondary control. The results suggest the need for a greater focus on the role of underlying processes or belief structures as factors that foster susceptibility to specific beliefs in gambling situations. Addressing and recognising the importance of these underlying factors may also have implications for cognitive therapy treatments for problem gambling.

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

    Science.gov (United States)

    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.

  5. The relationship between temporal phase discrimination ability and the frequency doubling illusion.

    Science.gov (United States)

    Vallam, Kunjam; Metha, Andrew B

    2007-12-20

    The frequency doubling illusion (FDI) occurs when a low spatial frequency sinusoidal grating is modulated at high temporal frequencies--its apparent spatial frequency increases. A recent study suggests that this illusion is perceived due to a frequency-dependent loss of temporal phase encoding ability. We sought to elucidate the relationship between temporal phase encoding and the FDI by exploring the spatiotemporal characteristics of temporal phase discrimination (TPD) thresholds using a novel stimulus comprising three grating patches presented simultaneously in a triangular pattern. A reference grating was presented superiorly, and six degrees below two gratings (one a copy of the reference) were each randomly presented in one of two fixed positions. The odd grating had abutting regions of spatial half-cycles with alternate half-cycles locked in temporal phase. The temporal phase difference between adjoining half-cycles was varied between 0 degrees and 180 degrees via QUEST staircase--subjects had to identify which lower stimulus appeared different from the reference grating. TPD thresholds were measured for 0.25, 0.50, and 2.20 cpd stimulus at six temporal frequencies (1 to 28 Hz) at 2x, 4x, and 8x orientation identification contrast thresholds. For all subjects, thresholds were variable at low contrasts. At higher contrasts, TPD thresholds increase for 0.25 and 0.50 cpd gratings with increasing flicker rate. These data support the idea that frequency-dependent loss of temporal phase encoding ability could possibly underlie the FDI.

  6. The Size-Weight Illusion is not anti-Bayesian after all: a unifying Bayesian account.

    Science.gov (United States)

    Peters, Megan A K; Ma, Wei Ji; Shams, Ladan

    2016-01-01

    When we lift two differently-sized but equally-weighted objects, we expect the larger to be heavier, but the smaller feels heavier. However, traditional Bayesian approaches with "larger is heavier" priors predict the smaller object should feel lighter; this Size-Weight Illusion (SWI) has thus been labeled "anti-Bayesian" and has stymied psychologists for generations. We propose that previous Bayesian approaches neglect the brain's inference process about density. In our Bayesian model, objects' perceived heaviness relationship is based on both their size and inferred density relationship: observers evaluate competing, categorical hypotheses about objects' relative densities, the inference about which is then used to produce the final estimate of weight. The model can qualitatively and quantitatively reproduce the SWI and explain other researchers' findings, and also makes a novel prediction, which we confirmed. This same computational mechanism accounts for other multisensory phenomena and illusions; that the SWI follows the same process suggests that competitive-prior Bayesian inference can explain human perception across many domains.

  7. Sensitivity to an Illusion of Sound Location in Human Auditory Cortex

    Directory of Open Access Journals (Sweden)

    Nathan C. Higgins

    2017-05-01

    Full Text Available Human listeners place greater weight on the beginning of a sound compared to the middle or end when determining sound location, creating an auditory illusion known as the Franssen effect. Here, we exploited that effect to test whether human auditory cortex (AC represents the physical vs. perceived spatial features of a sound. We used functional magnetic resonance imaging (fMRI to measure AC responses to sounds that varied in perceived location due to interaural level differences (ILD applied to sound onsets or to the full sound duration. Analysis of hemodynamic responses in AC revealed sensitivity to ILD in both full-cue (veridical and onset-only (illusory lateralized stimuli. Classification analysis revealed regional differences in the sensitivity to onset-only ILDs, where better classification was observed in posterior compared to primary AC. That is, restricting the ILD to sound onset—which alters the physical but not the perceptual nature of the spatial cue—did not eliminate cortical sensitivity to that cue. These results suggest that perceptual representations of auditory space emerge or are refined in higher-order AC regions, supporting the stable perception of auditory space in noisy or reverberant environments and forming the basis of illusions such as the Franssen effect.

  8. Light refraction by water as a rationale for the Poggendorff illusion

    CERN Document Server

    Bozhevolnyi, Sergey I

    2015-01-01

    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 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 7 participants, each analysing 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 il...

  9. Decreased Corticospinal Excitability after the Illusion of Missing Part of the Arm

    Science.gov (United States)

    Kilteni, Konstantina; Grau-Sánchez, Jennifer; Veciana De Las Heras, Misericordia; Rodríguez-Fornells, Antoni; Slater, Mel

    2016-01-01

    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. PMID:27148005

  10. The Human Touch: Skin Temperature during the Rubber Hand Illusion in Manual and Automated Stroking Procedures

    Science.gov (United States)

    Rohde, Marieke; Wold, Andrew; Karnath, Hans-Otto; Ernst, Marc O.

    2013-01-01

    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 (PHANToMTM 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. PMID:24260454

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

    Science.gov (United States)

    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.

  12. Musicians have enhanced audiovisual multisensory binding: experience-dependent effects in the double-flash illusion.

    Science.gov (United States)

    Bidelman, Gavin M

    2016-10-01

    Musical training is associated with behavioral and neurophysiological enhancements in auditory processing for both musical and nonmusical sounds (e.g., speech). Yet, whether the benefits of musicianship extend beyond enhancements to auditory-specific skills and impact multisensory (e.g., audiovisual) processing has yet to be fully validated. Here, we investigated multisensory integration of auditory and visual information in musicians and nonmusicians using a double-flash illusion, whereby the presentation of multiple auditory stimuli (beeps) concurrent with a single visual object (flash) induces an illusory perception of multiple flashes. We parametrically varied the onset asynchrony between auditory and visual events (leads and lags of ±300 ms) to quantify participants' "temporal window" of integration, i.e., stimuli in which auditory and visual cues were fused into a single percept. Results show that musically trained individuals were both faster and more accurate at processing concurrent audiovisual cues than their nonmusician peers; nonmusicians had a higher susceptibility for responding to audiovisual illusions and perceived double flashes over an extended range of onset asynchronies compared to trained musicians. Moreover, temporal window estimates indicated that musicians' windows (audiovisual binding. Collectively, findings indicate a more refined binding of auditory and visual cues in musically trained individuals. We conclude that experience-dependent plasticity of intensive musical experience extends beyond simple listening skills, improving multimodal processing and the integration of multiple sensory systems in a domain-general manner.

  13. An Auditory Illusion of Proximity of the Source Induced by Sonic Crystals.

    Directory of Open Access Journals (Sweden)

    Ignacio Spiousas

    Full Text Available In this work we report an illusion of proximity of a sound source created by a sonic crystal placed between the source and a listener. This effect seems, at first, paradoxical to naïve listeners since the sonic crystal is an obstacle formed by almost densely packed cylindrical scatterers. Even when the singular acoustical properties of these periodic composite materials have been studied extensively (including band gaps, deaf bands, negative refraction, and birrefringence, the possible perceptual effects remain unexplored. The illusion reported here is studied through acoustical measurements and a psychophysical experiment. The results of the acoustical measurements showed that, for a certain frequency range and region in space where the focusing phenomenon takes place, the sonic crystal induces substantial increases in binaural intensity, direct-to-reverberant energy ratio and interaural cross-correlation values, all cues involved in the auditory perception of distance. Consistently, the results of the psychophysical experiment revealed that the presence of the sonic crystal between the sound source and the listener produces a significant reduction of the perceived relative distance to the sound source.

  14. The Folded Paper Size Illusion: Evidence of Inability to Perceptually Integrate More Than One Geometrical Dimension

    Science.gov (United States)

    2016-01-01

    The folded paper-size illusion is as easy to demonstrate as it is powerful in generating insights into perceptual processing: First take two A4 sheets of paper, one original sized, another halved by folding, then compare them in terms of area size by centering the halved sheet on the center of the original one! We perceive the larger sheet as far less than double (i.e., 100%) the size of the small one, typically only being about two thirds larger—this illusion is preserved by rotating the inner sheet and even by aligning it to one or two sides, but is dissolved by aligning both sheets to three sides, here documented by 88 participants’ data. A potential explanation might be the general incapability of accurately comparing more than one geometrical dimension at once—in everyday life, we solve this perceptual-cognitive bottleneck by reducing the complexity of such a task via aligning parts with same lengths. PMID:27698977

  15. Optics/Optical Diagnostics Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Optics/Optical Diagnostics Laboratory supports graduate instruction in optics, optical and laser diagnostics and electro-optics. The optics laboratory provides...

  16. 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.

  17. 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.

  18. Fixating on the size-speed illusion of approaching railway trains: What we can learn from our eye movements.

    Science.gov (United States)

    Clark, Helen E; Perrone, John A; Isler, Robert B; Charlton, Samuel G

    2017-02-01

    Railway level crossing collisions have recently been linked to a size-speed illusion where larger objects such as trains appear to move slower than smaller objects such as cars. An explanation for this illusion has centred on observer eye movements - particularly in relation to the larger, longer train. A previous study (Clark et al., 2016) found participants tend to make initial fixations to locations around the visual centroid of a moving vehicle; however individual eye movement patterns tended to be either fixation-saccade-fixation type, or smooth pursuit. It is therefore unknown as to which type of eye movement contributes to the size-speed illusion. This study isolated fixation eye movements by requiring participants to view computer animated sequences in a laboratory setting, where a static fixation square was placed in the foreground at one of two locations on a train (front and centroid). Results showed that even with the square placed around the front location of a vehicle, participants still underestimated the speed of the train relative to the car and underestimation was greater when the square was placed around the visual centroid of the train. Our results verify that manipulation of eye movement behaviour can be effective in reducing the magnitude of the size-speed illusion and propose that interventions based on this manipulation should be designed and tested for effectiveness.

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  1. 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

  2. Differential effects of a visual illusion on online visual guidance in a stable environment and online adjustments to perturbations

    NARCIS (Netherlands)

    Caljouw, Simone R.; van der Kamp, John; Lijster, Moniek; Savelsbergh, Geert J. P.

    2011-01-01

    In the reported, experiment participants hit a ball to aim at the vertex of a Miiller-Lyer configuration. This configuration either remained stable, changed its shaft length or the orientation of the tails during movement execution. A significant illusion bias was observed in all perturbation condit

  3. Observational Learning from Animated Models: Effects of Studying-Practicing Alternation and Illusion of Control on Transfer

    NARCIS (Netherlands)

    Wouters, Pieter; Paas, Fred; Van Merriënboer, Jeroen

    2008-01-01

    Wouters, P. J. M., Paas, F., & Van Merriënboer, J. J. G. (2010). Observational learning from animated models: effects of studying-practicing alternation and illusion of control on transfer. Instructional Science, 38(1), 89-104. doi:10.1007/s11251-008-9079-0

  4. The neuronal correlates of mirror therapy: an fMRI study on mirror induced visual illusions in patients with stroke.

    Science.gov (United States)

    Michielsen, Marian E; Smits, Marion; Ribbers, Gerard M; Stam, Henk J; van der Geest, Jos N; Bussmann, Johannes B J; Selles, Ruud W

    2011-04-01

    To investigate the neuronal basis for the effects of mirror therapy in patients with stroke. 22 patients with stroke participated in this study. The authors used functional MRI to investigate neuronal activation patterns in two experiments. In the unimanual experiment, patients moved their unaffected hand, either while observing it directly (no-mirror condition) or while observing its mirror reflection (mirror condition). In the bimanual experiment, patients moved both hands, either while observing the affected hand directly (no-mirror condition) or while observing the mirror reflection of the unaffected hand in place of the affected hand (mirror condition). A two-factorial analysis with movement (activity vs rest) and mirror (mirror vs no mirror) as main factors was performed to assess neuronal activity resultant of the mirror illusion. Data on 18 participants were suitable for analysis. Results showed a significant interaction effect of movement×mirror during the bimanual experiment. Activated regions were the precuneus and the posterior cingulate cortex (pmirror illusion in patients with stroke, the authors showed that during bimanual movement, the mirror illusion increases activity in the precuneus and the posterior cingulate cortex, areas associated with awareness of the self and spatial attention. By increasing awareness of the affected limb, the mirror illusion might reduce learnt non-use. The fact that the authors did not observe mirror-related activity in areas of the motor or mirror neuron system questions popular theories that attribute the clinical effects of mirror therapy to these systems.

  5. The neuronal correlates of mirror illusion in children with spastic hemiparesis: a study with functional magnetic resonance imaging.

    Science.gov (United States)

    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 (pmirror illusion were observed in unimanual experiments and in healthy participants. Mirror illusion in children/adolescents with hemiparesis 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.

  6. The neuronal correlates of mirror illusion in children with spastic hemiparesis: a study with functional magnetic resonance imaging.

    OpenAIRE

    Weisstanner, C.; Saxer, S; Wiest, R.; Kaelin-Lang, A.; Newman, C J; Steinlin, M.; Grunt, S

    2017-01-01

    AIM 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. METHOD 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 ...

  7. 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

  8. 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

  9. The Rubber Hand Illusion in Children with Autism Spectrum Disorders: Delayed Influence of Combined Tactile and Visual Input on Proprioception

    Science.gov (United States)

    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…

  10. Determinants of the direction illusion: motion speed and dichoptic presentation interact to reveal systematic individual differences in sign.

    Science.gov (United States)

    Chen, Tony T; Maloney, Ryan T; Clifford, Colin W G

    2014-07-17

    When two fields of dots with different directions of movement are presented in tandem, the perceived direction of one is biased by the presence of the other. Although this ‘‘direction illusion’’ typically involves repulsion, with an exaggeration of the perceived angular difference in direction between the dot fields, attraction effects, where the perceived difference is reduced, have also been found under certain presentation conditions. Earlier literature has been inconsistent, and there is debate surrounding the nature of the interactions that facilitate the direction illusion, as well as whether they occur at a local or global stage of the motion processing hierarchy. Here we measured the operating characteristics of the direction illusion by parametrically varying inducer contrast and coherence while examining the effects of stimulus speed and dichoptic presentation. It was found that the magnitude and sign of the direction illusion differed substantially from earlier research. Furthermore, there appeared to be significant interindividual variability, with dichoptic presentation producing an attractive rather than repulsive direction illusion in some participants.

  11. 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.

  12. Prediction, postdiction, and perceptual length contraction: a Bayesian low-speed prior captures the cutaneous rabbit and related illusions

    Directory of Open Access Journals (Sweden)

    Daniel eGoldreich

    2013-05-01

    Full Text Available Illusions provide a window into the brain’s perceptual strategies. In certain illusions, an ostensibly task-irrelevant variable influences perception. For example, in touch as in audition and vision, the perceived distance between successive punctate stimuli reflects not only the actual distance but curiously the inter-stimulus time. Stimuli presented at different positions in rapid succession are drawn perceptually towards one another. This effect manifests in several illusions, among them the startling cutaneous rabbit, in which taps delivered to as few as two skin positions appear to hop progressively from one position to the next, landing in the process on intervening areas that were never stimulated. Here we provide an accessible step-by-step exposition of a Bayesian perceptual model that replicates the rabbit and related illusions. The Bayesian observer optimally joins uncertain estimates of spatial location with the expectation that stimuli tend to move slowly. We speculate that this expectation – a Bayesian prior – represents the statistics of naturally occurring stimuli, learned by humans through sensory experience. In its simplest form, the model contains a single free parameter, tau: a time constant for space perception. We show that the Bayesian observer incorporates both pre- and post-dictive inference. Directed spatial attention affects the prediction-postdiction balance, shifting the model’s percept towards the attended location, as observed experimentally in humans. Applying the model to the perception of multi-tap sequences, we show that the low-speed prior fits perception better than an alternative, low-acceleration prior. We discuss the applicability of our model to related tactile, visual, and auditory illusions. To facilitate future model-driven experimental studies, we present a convenient freeware computer program that implements the Bayesian observer; we invite investigators to use this program to create their own

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

    Directory of Open Access Journals (Sweden)

    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

  14. 视错觉在平面海报设计中的运用%The Application of Visual Illusion in Poster Design

    Institute of Scientific and Technical Information of China (English)

    达志翔

    2013-01-01

    视错觉在平面海报设计中以极富趣味性的简单图案造型形成了颠覆常态的视觉效果。几何视错觉、动态视错觉、光渗视错觉都可以在平面海报设计中给人以较强的视觉冲击力。%Visual illusion ,in flat poster design ,with its unique interests ,and simple pictures subverts the normal visual effects .Geometric visual illusion ,dynamic visual illusion and light visual illusion all can generate strong visual impact in flat poster design .

  15. An Exploratory Study of the Relationship Between Digit Ratio, Illusion of Control, and Risk-Taking Behavior Among Chinese College Students.

    Science.gov (United States)

    Lam, Desmond; Ozorio, Bernadete

    2015-12-01

    Previous studies on the relationship between digit ratio and risk-taking mainly focused on western subjects. Moreover, no researcher has examined the concurrent effect of digit ratio and illusion of control on gambling behavior. This exploratory study investigates the relationship between digit ratio, illusion of control and risk-taking behavior of Chinese subjects. Sixty-six students from a Chinese university were invited to answer a questionnaire and play a purposefully-designed betting game. The results show that the subjects' risk-taking level, measured in terms of average betting amount, is negatively correlated to their digit ratio but not to their illusion of control score. Moreover, there is no significant association between the subjects' digit ratio and illusion of control score. These preliminary findings will have useful implications to gaming regulators and businesses.

  16. A possible low-level explanation of "temporal dynamics of brightness induction and White's illusion"

    CERN Document Server

    Karmakar, Subhajit

    2009-01-01

    Based upon physiological observation on time dependent orientation selectivity in the cells of macaque's primary visual cortex together with the psychophysical studies on the tuning of orientation detectors in human vision we suggest that time dependence in brightness perception can be accommodated through the time evolution of cortical contribution to the orientation tuning of the ODoG filter responses. A set of Difference of Gaussians functions has been used to mimic the time dependence of orientation tuning. The tuning of orientation preference and its inversion at a later time have been considered in explaining qualitatively the temporal dynamics of brightness perception observed in "Brief presentations reveal the temporal dynamics of brightness induction and White's illusion" for 58 and 82 ms of stimulus exposure.

  17. Directionally Hiding Objects and Creating Illusions at Visible Wavelengths by Holography

    Science.gov (United States)

    Cheng, Qiluan; Wu, Kedi; Shi, Yile; Wang, Hui; Wang, Guo Ping

    2013-06-01

    Invisibility devices have attracted considerable attentions in the last decade. In addition to invisibility cloaks, unidirectional invisibility systems such as carpet-like cloaks and parity-time symmetric structures are also inspiring some specific researching interests due to their relatively simplifying design. However, unidirectional invisibility systems worked generally in just one certain illumination direction. Here, based on time-reversal principle, we present the design and fabrication of a kind of all-dielectric device that could directionally cancel objects and create illusions as the illuminating light was from different directions. Our devices were experimentally realized through holographic technology and could work for macroscopic objects with any reasonable size at visible wavelengths, and hence may take directional invisibility technology a big step towards interesting applications ranging from magic camouflaging, directional detection to super-resolution biomedical imaging.

  18. Illusion thermal device based on material with constant anisotropic thermal conductivity for location camouflage

    Science.gov (United States)

    Hou, Quanwen; Zhao, Xiaopeng; Meng, Tong; Liu, Cunliang

    2016-09-01

    Thermal metamaterials and devices based on transformation thermodynamics often require materials with anisotropic and inhomogeneous thermal conductivities. In this study, still based on the concept of transformation thermodynamics, we designed a planar illusion thermal device, which can delocalize a heat source in the device such that the temperature profile outside the device appears to be produced by a virtual source at another position. This device can be constructed by only one kind of material with constant anisotropic thermal conductivity. The condition which should be satisfied by the device is provided, and the required anisotropic thermal conductivity is then deduced theoretically. This study may be useful for the designs of metamaterials or devices since materials with constant anisotropic parameters have great facility in fabrication. A prototype device has been fabricated based on a composite composed by two naturally occurring materials. The experimental results validate the effectiveness of the device.

  19. “Exorcist Illusion”: Twisting Necks in the Hollow-Face and Hollow-Torso Illusions

    Directory of Open Access Journals (Sweden)

    Thomas V. Papathomas

    2012-12-01

    Full Text Available We combine a convex facial mask with a concave torso—or vice versa—thus creating a single rigid object with a transition area at the neck, where convexity changes to concavity. This combination creates stunning illusions when the rigid object is set to motion. The two simplest effects are (1 when the object is rotated about its axis, the head appears to twist with respect to the torso, as in “The Exorcist” film (2 when it is rotated around an axis parallel to the shoulders, the head appears to hinge around the torso. More complex illusory effects result from more complex motions. The involvement of higher-level perceptual processes may account for the illusory effects.

  20. Design of a 3-dimensional visual illusion speed reduction marking scheme.

    Science.gov (United States)

    Liang, Guohua; Qian, Guomin; Wang, Ye; Yi, Zige; Ru, Xiaolei; Ye, Wei

    2017-03-01

    To determine which graphic and color combination for a 3-dimensional visual illusion speed reduction marking scheme presents the best visual stimulus, five parameters were designed. According to the Balanced Incomplete Blocks-Law of Comparative Judgment, three schemes, which produce strong stereoscopic impressions, were screened from the 25 initial design schemes of different combinations of graphics and colors. Three-dimensional experimental simulation scenes of the three screened schemes were created to evaluate four different effects according to a semantic analysis. The following conclusions were drawn: schemes with a red color are more effective than those without; the combination of red, yellow and blue produces the best visual stimulus; a larger area from the top surface and the front surface should be colored red; and a triangular prism should be painted as the graphic of the marking according to the stereoscopic impression and the coordination of graphics with the road.