Haptic perceptual illusions

Visual illusions occur around us all the time, which present in nature and appear when you least expect it. It is well known that visual illusions can have a dramatic effect upon our visual perception of an object 's size and position. However, whether visual illusions have a similar influence on visual guided action or not, it remains the subject of much debate. The purpose of this study is to explore whether the visual information used to identify and categorize an object would be similar to the visual information used to plan and control visually guided movements directed toward that object. The outcome of this study will be helpful for designers to understand our visual information system and apply that knowledge to the design practice. In order to achieve the purpose of this study mentioned above, three visual illusions as the experiment's apparatus are applied to examine the relative effect of visual illusions on both the visual perceived center of an object and the position of a grasp on that object when a balanced lift is required. The results of the experiment show that (1) Illusions influence both the perceived and the grasped estimates of the center position, but the grasp center is more veridical; (2) Judd-illusion, one of the three visual illusions, has a bigger degree of effect than two other illusions on both the perceived and the grasped estimates of the center position; (3) By providing the participants with a mean to guide their visual perception of these illusions, the errors from the estimation of the center position can be significantly reduced.

Luria (Luria, Cognitive development: Its cultural and social foundations, Harvard University Press, 1976) famously observed that people who never learnt to read and write do not perceive visual illusions. We conducted a conceptual replication of the Luria study of the effect of literacy on the processing of visual illusions. We designed two carefully controlled experiments with 161 participants with varying literacy levels ranging from complete illiterates to high literates in Chennai, India. Accuracy and reaction time in the identification of visual shape and color illusions and the identification of appropriate control images were measured. Separate statistical analyses of Experiments 1 and 2 as well as pooled analyses of both experiments do not provide any support for the notion that literacy affects the perception of visual illusions. Our large sample, carefully controlled study strongly suggests that literacy does not meaningfully affect the identification of visual illusions and raises some questions about other reports of cultural effects on illusion perception.

Optical illusions have long been used in behavioural studies to investigate the perceptual mechanisms underlying vision in animals. So far, three studies have focused on ungulates, providing evidence that they may be susceptible to some optical illusions, in a way similar to humans. Here, we used two food-choice tasks to study susceptibility to the Müller-Lyer and Delboeuf illusions in 17 captive individuals belonging to four ungulate species (Lama guanicoe, Lama glama, Ovis aries, Capra hircus). At the group level, there was a significant preference for the longer/larger food over the shorter/smaller one in control trials. Additionally, the whole group significantly preferred the food stick between two inward arrowheads over an identical one between two outward arrowheads in experimental trials of the Müller-Lyer task, and also preferred the food on the smaller circle over an identical one on the larger circle in the experimental trials of the Delboeuf task. Group-level analyses further showed no significant differences across species, although at the individual level we found significant variation in performance. Our findings suggest that, in line with our predictions, ungulates are overall susceptible to the Müller-Lyer and the Delboeuf illusions, and indicate that the perceptual mechanisms underlying size estimation in artiodactyls might be similar to those of other species, including humans.

Systematic review of visual illusions in schizophrenia

Visual illusions are fascinating because visual perception misjudges the actual physical properties of an image or a scene. This paper examines the perception of visual illusions in three-dimensional space. Six diverse visual illusions were implemented for both immersive virtual reality and monitor based environments. A user-study with 30 healthy participants took place in laboratory conditions comparing the perceptual effects of the two different mediums. Experimental data were collected from both a simple ordering method and electrical activity of the brain. Results showed unexpected outcomes indicating that only some of the illusions have a stronger effect in immersive virtual reality, others in monitor based environments while the rest with no significant effects.

The perception and imagery of landmarks activate similar content‐dependent brain areas, including occipital and temporo‐medial brain regions. However, how these areas interact during visual perception and imagery of scenes, especially when recollecting their spatial location, remains unknown. Here, we combined functional magnetic resonance imaging (fMRI), resting‐state functional connectivity (rs‐fc), and effective connectivity to assess spontaneous fluctuations and task‐induced modulation of signals among regions entailing scene‐processing, the primary visual area and the hippocampus (HC), responsible for the retrieval of stored information. First, we functionally defined the scene‐selective regions, that is, the occipital place area (OPA), the retrosplenial complex (RSC) and the parahippocampal place area (PPA), by using the face/scene localizer, observing that two portions of the PPA—anterior and posterior PPA—were consistently activated in all subjects. Second, the rs‐fc analysis (n = 77) revealed a connectivity pathway similar to the one described in macaques, showing separate connectivity routes linking the anterior PPA with RSC and HC, and the posterior PPA with OPA. Third, we used dynamic causal modelling to evaluate whether the dynamic couplings among these regions differ between perception and imagery of familiar landmarks during a fMRI task (n = 16). We found a positive effect of HC on RSC during the retrieval of imagined places and an effect of occipital regions on both RSC and pPPA during the perception of scenes. Overall, we propose that under similar functional architecture at rest, different neural interactions take place between regions in the occipito‐temporal higher‐level visual cortex and the HC, subserving scene perception and imagery.

Recently MR (Mixed Reality) techniques are used in many fields, and one of them is work support. Work support using MR techniques can display work instructions directly in the work space and help user to work effectively especially in assembling tasks. MR work support for assembling tasks often uses HMD (Head Mounted Display) to construct MR environment. However, there are some problems for the use of HMD, such as a burden to the head, a narrow view and a motion picture sickness. One of the techniques to solve such problems is pepper's ghost which is an optical illusion using a glass. In this paper, we propose the naked eye MR work supporting system for assembling tasks using pepper's ghost. This system enables a beginner to assemble some blocks into one object by the naked eye with a few burdens.

Visual illusions have been studied in many non-human species, spanning a wide range of biological and methodological variables. While early reviews have proved useful in providing an overview of the field, they have not been accompanied by quantitative analysis to systematically evaluate the contribution of biological and methodological moderators on the proportion of illusory choice. In the current meta-analytical study, we confirm that geometrical visual illusion perception is a general phenomenon among non-human animals. Additionally, we found that studies testing birds report stronger illusion perception compared to other classes, as do those on animals with lateral-positioned eyes compared to animals with forward-facing eyes. In terms of methodological choices, we found a positive correlation between the number of trials during training or testing and the effect sizes, while studies with larger samples report smaller effect sizes. Despite studies that trained animals with artificial stimuli showing larger effect sizes compared with those using spontaneous testing with naturalistic stimuli, like food, we found more recent studies prefer spontaneous choice over training. We discuss the challenges and bottlenecks in this area of study, which, if addressed, could lead to more successful advances in the future.

The strength of certain visual illusions, including contrast-contrast and apparent motion, is weakened in individuals with schizophrenia. Such phenomena have been interpreted as the impaired integration of inhibitory and excitatory neural responses, and impaired top-down feedback mechanisms. To investigate whether and how these factors influence the perceived contrast-contrast and apparent motion illusions in individuals with schizophrenia, we propose a two-layer network, with top-down feedback from layer 2 to layer 1 that can model visual receptive fields (RFs) and their inhibitory and excitatory subfields. Our neural model suggests that illusion perception changes in individuals with schizophrenia can be influenced by altered top-down mechanisms and the organization of the on-center off-surround receptive fields. Alteration of the RF inhibitory surround and/or the excitatory center can replicate the difference of illusion precepts between individuals with schizophrenia within certain clinical states and normal controls. The results show that the simulated top-down feedback modulation enlarges the difference of the model illusion representations, replicating the difference between the two groups. We propose that the heterogeneity of visual and in general sensory processing in certain clinical states of schizophrenia can be largely explained by the degree of top-down feedback reduction, emphasizing the critical role of top-down feedback in illusion perception, and to a lesser extent on the imbalance of excitation/inhibition. Our neural model provides a mechanistic explanation for the modulated visual percepts of contrast-contrast and apparent motion in schizophrenia with findings that can explain a broad range of visual perceptual observations in previous studies. The two-layer motif of the current model provides a general framework that can be tailored to investigate subcortico-cortical (such as thalamocortical) and cortico-cortical networks, bridging neurobiological changes in schizophrenia and perceptual processing.

The Journal of Scottish Philosophy, 1 (2) 2003, 117–133 ISSN 1479-6651 Reid maintained that the perceptions that we obtain from the senses of smell, taste, hearing, and touch are “suggested” by corresponding sensations. However, he made an exception for the sense of vision. According to Reid, our perceptions of the real figure, position, and magnitude of bodies are suggested by their visible appearances, which are not sensations but objects of perception in their own right. These visible appearances have figure, position, and magnitude, as well as “colour”, and up to now, the standard view among Reid scholars (including one of us) has been that Reid maintained that our perceptions of visible figure, position, and magnitude are also not suggested by any sensation. They are instead suggested by the material impression made by light on the retina. In what follows, we refer to this as the “standard interpretation” of Reid’s position on the perception of visible figure. Gideon Yaffe challenges the standard interpretation. According to Yaffe, Reid believed that our perceptions of visible figure are suggested by corresponding visual sensations, specifically, by sensations of color. This is a good thing, according to Yaffe, because the standard interpretation is “implausible”. The most valuable feature of Yaffe’s paper is the attention it draws to a number of passages that pose problems for proponents of the standard interpretation. Yaffe shows that the passages that appear to endorse the standard interpretation contain incidental comments that render their interpretation questionable, and he also shows that there are passages where Reid appears to endorse what we call (for the sake of contrast), the Yaffe interpretation – that our perceptions of visible figure are suggested by sensations of color. At the very least, therefore, Yaffe has posed an interpretative difficulty for those wishing to endorse the standard interpretation. We do not think that this difficulty is insuperable, however. We also think that the Yaffe interpretation could not possibly be correct. In what follows we do two main things: First, we look at the problem of the perception of visible figure independently of reference to the texts where Reid

Animated optical illusions – how to effectively create them and how they are perceived

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

Understanding how the human visual system recognizes objects is one of the key challenges in neuroscience. Inspired by a large body of physiological evidence, a general class of recognition models has emerged, which is based on a hierarchical organization of visual processing, with succeeding stages being sensitive to image features of increasing complexity. However, these models appear to be incompatible with some well-known psychophysical results. Prominent among these are experiments investigating recognition impairments caused by vertical inversion of images, especially those of faces. It has been reported that faces that differ 'featurally' are much easier to distinguish when inverted than those that differ 'configurally'; a finding that is difficult to reconcile with the physiological models. Here, we show that after controlling for subjects' expectations, there is no difference between 'featurally' and 'configurally' transformed faces in terms of inversion effect. This result reinforces the plausibility of simple hierarchical models of object representation and recognition in the cortex.

The spatial context in which we view a visual stimulus strongly determines how we perceive the stimulus. In the visual tilt illusion, the perceived orientation of a visual grating is affected by the orientation signals in its surrounding context. Conceivably, the spatial context in which a visual grating is perceived can be defined by interactive multisensory information rather than visual signals alone. Here, we tested the hypothesis that tactile signals engage the neural mechanisms supporting visual contextual modulation. Because tactile signals also convey orientation information and touch can selectively interact with visual orientation perception, we predicted that tactile signals would modulate the visual tilt illusion. We applied a bias-free method to measure the tilt illusion while testing visual-only, tactile-only or visuo-tactile contextual surrounds. We found that a tactile context can influence visual tilt perception. Moreover, combining visual and tactile orientation information in the surround results in a larger tilt illusion relative to the illusion achieved with the visual-only surround. These results demonstrate that the visual tilt illusion is subject to multisensory influences and imply that non-visual signals access the neural circuits whose computations underlie the contextual modulation of vision.

This paper presents a systematic exposition of the general structure of visual constancies and illusions, including the introduction of a number of conceptual distinctions, illustrated by many examples. The study of these phenomena involves the distal, the proximal, and the phenomenal domain. The relations of concordance and discordance between pairs of domains are defined, followed by the definitions of four visual modes (concordant, proximal, constancy, illusion) as particular constellations of concordance-discordance relations between all three domains. Constancies and illusions are characterized by proximal-phenomenal discordance. Attributes of entities of visual domains are divided into the geometric (size, shape, location, orientation) and the photometric (reflectance, illumination) class. The phenomenal domain involves two types of attributes, one group distally and the other proximally focused. Research on both constancies and illusions can be described as involving the study of the effects of two independent variables on a dependent variable. The first independent variable (target variable) is a distal attribute, such as size, shape etc. In constancy studies, the second independent variable (confound variable), is a variable such as distance, orientation etc, that, together with the confound variable, affects the corresponding proximal variable (such as proximal size, shape etc). In illusion studies, confound variables do not affect the proximal variables, but do affect the corresponding phenomenal variables. The main part of the paper consists in the descriptions of studies of constancies and illusions of size, shape, location, orientation, and achromatic and chromatic color, all presented in a common format, which facilitates the comparison of their similarities and differences. The importance of presentation conditions (full-cue versus reduced cue) and instruction type (distally versus proximally focused) is stressed. Finally, salient cases are pointed out in which relations between phenomenal variables tend to take a form qualitatively similar to the relation of the corresponding non-phenomenal variables.