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

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.

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.

The way we experience space has a direct relationship to the way we perceive it, as evidenced by the ways that space has been represented in painting throughout history. My research is concerned with the representation of space in contemporary painting. Contemporary experiences of space through new media screens offer painters a unique challenge that requires them to think about representing space in new ways. My research focuses on the role of the window in painting, a device that has confirmed painters’ preoccupation with representing space on a two-dimensional plane. I provide an historical overview that establishes the window as an important spatial and metaphorical concern within painting. I draw a connection between the window and Plato’s cave as a frame of representation. In the context of this research, ‘space’ refers to a painterly space which includes both illusory space and actual physical/material space. Whereas Gilles Deleuze defines these different kinds of space as either ‘haptic’ or ‘optic space’, I use the term ‘unstable space’ to describe that which occurs when both ‘haptic’ and ‘optic space’ coexist on a picture plane. In considering Plato’s cave as a window or frame of representation, I recognise the demarcation of key spatial and representational concepts related to the window in painting. As with Plato’s cave, the window demarcates binary opposites that have structured much subsequent thinking about art, such as interiority/exteriority, nature/culture, illusion/reality. Through Plato’s theories, I specifically draw attention to the dualist structure of his belief system that posits tensions between interior and exterior, reality and illusion, nature and culture. I establish the term ‘unstable space’ through examining the theories of Deleuze and Jacques Derrida that deconstruct Plato’s writing. Their theories offer a means by which to construct new meanings within the space of painting, as they emphasise the instability of the binaries afforded by Plato’s philosophy and instead suggest the possibilities of multiplicity. The contemporary ‘windows’ of media screens significantly shift the metaphor of the singular window to the multiplicity of windows within windows. This multiplicity reflects the way we currently experience space and the effect this has on the thinking of space in contemporary painting practice. In this way, painting’s material dimension and illusory space can be explored not in terms of binary oppositions but as complementaries. Having traced the development of the window as an important representational device in painting, I propose that the window can be used as a mechanism to explore the ‘unstable space’ through painting. This space operates between spatial and representational theory. Through the analysis of specific works of art by contemporary artists chosen as exemplars in the field of painting, I argue that the unstable space can be created solely in the medium of paint. My research extends understandings of space as represented within the limits of a two-dimensional surface. The representation of space within my painting practice results from my reimagining of the window as an unstable space, my exploring of the perception and representation of ambiguous space, and my engaging with pictorial illusion through abstraction. Explicitly, the studio research found that the screen or window was able to act as a metaphor for the body and as such effectively articulate the experience of interiority and exteriority, surface and figure, ground and distance.

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.

A Correlational evaluation of the misapplied constancy theory of geometric optical illusions

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.

Visuospatial assessment by virtual 3D radial optic flow illusion in healthy aging, mild Alzheimer’s Disease (AD), and Pre-Deep-Brain Stimulation (DBS) Parkinson’s disease (PD) subjects

The brain represents the state of the world around us based upon a stream of ambiguous sensory data. This requires the integration of different sources of information, including information received from different sense modalities, and information drawn from past experience. Bayesian theories of perception provide an approach to characterising how systematic differences in the probabilistic integration of information in the brain may underlie the differences that occur between individuals in their perceptual experience. The present thesis explores how perceptual, motor and social aspects of autism spectrum disorder (ASD) may emerge from variation in the neurocognitive processes described by Bayesian theories. A focus is on the predictive processing model of brain function, which links Bayesian theories of perception to neural mechanisms. The thesis includes empirical studies that examine perceptual, sensorimotor and cognitive aspects of ASD. ASD and nonclinical autistic traits are first examined in the context of body perception; concerning, specifically, how the brain represents the state of the limbs based on visual, tactile and proprioceptive information, and how this sensory information is integrated with prior expectations regarding the body. These processes are investigated using a multisensory perceptual illusion: the rubber hand illusion. ASD is associated with a largely typical perceptual experience of this illusion, indicating intact multisensory integration in the context of body representation. A reduced influence of the illusion on motor function, however, supports a difference in ASD in the integration of expectations for limb position (influenced by the illusion) with conflicting sensory (proprioceptive) signals. The integration of incoming information with existing expectations about the environment is also examined in the context of statistical learning. A computerised task is developed to assess the integration of iterative feedback with prior information as participants predict the location of a noisy set of visual markers. The hypothesis tested is that features of ASD are associated with a persistently higher weighting of incoming information in driving inference, at the expense of expectations developed from recent experience; in this more cognitive context, these data provide evidence against this hypothesis, suggesting that a more context-dependent atypicality in information processing in ASD is more likely than that initially hypothesised. The thesis also develops theoretical and philosophically-relevant treatments of how the symptoms of ASD may emerge from differences in brain function characterised within a Bayesian framework. This includes drawing on recent theoretical developments regarding the role of volatility processing and action in maintaining optimal inference on the environment. In addition, models of Bayesian inference in the brain can be extended to the social domain. For instance, the process of representing the mental states of other people (i.e., theory of mind) can be cast in terms of implicit inference on the external causes of sensory signals. In light of these expanded models of predictive processing, the differences in information processing hypothesised to occur in ASD have implications not just for perception, but also for motor behaviours, social cognition and social interaction. The overall view that emerges is that diverse aspects of ASD may be captured in terms of how incoming sensory signals are integrated, in a probabilistic manner, with the brain’s hierarchical and multimodal model of its environment. A promising direction for this field is in developing this idea in the context of action (i.e., active inference) and more recent models of how the brain estimates the optimal weighting of sensory information. This area of research has the potential to provide a nuanced perspective on the neurocognitive basis of ASD and the relationship between sensory mechanisms and autistic behaviours.

Perceptual illusions refer to systematically oriented errors in the perception of figures or scenes, and these errors are observed in almost all people. For centuries, they have been called ‘opto-geometric illusions’ because it was thought that they concerned only visual perception. Although visual errors are relatively rare, comments and questions about visual illusions are found as early as in the Greek and Roman literature. In scientific psychology, the theoretical and practical problems raised by these deformations have been intensively studied since the end of the 19th Century, and the elements of the figure inducing each error are now identified. However, there is no general theory explaining all the visual illusions. Instead, each figure must be analysed in order to determine the specific processes leading to the error. KeywordsVisual IllusionPerceptual ErrorHaptic PerceptionExploratory MovementPonzo IllusionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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.

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.

Systematic review of visual illusions in schizophrenia

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 effect of unilateral brain lesions on perception of visual illusions

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.