Visual Illusions Research Articles

A Study on the Relationship Between Spiral Motion Illusions and Anxiety Levels: A Comprehensive Analysis of Neural Activity and Visual Stimuli

Abstract. Spiral Motion Illusions (SMIs) are a fascinating phenomenon where static images create a compelling sense of motion, tricking the brain into perceiving movement where there is none. This study investigates the relationship between SMIs and anxiety levels, aiming to uncover how these visual illusions might influence emotional states. The experimental design involved exposing thirty-one participants to two distinct types of SMIsthe "rotating snakes" and "rotating ad-lib" imageswithin a controlled environment. Anxiety levels were assessed both before and after exposure using standardized questionnaires, while neural activity was continuously monitored through the ThinkGear ASIC Module (TGAM) to capture real-time brainwave patterns. The results revealed significant changes in anxiety levels, with each type of SMI eliciting unique neural responses. The "rotating snakes" illusion, characterized by dynamic color contrast, and the "rotating ad-lib" images, defined by contrasting colors, produced distinct patterns of anxiety-related brainwave activity. These findings provide valuable insights into the intricate ways that visual illusions can influence emotional states, particularly anxiety, and highlight the potential of SMIs as tools for both psychological research and therapeutic applications. This study advances our understanding of the neural mechanisms underlying anxiety and offers a new perspective on how visual stimuli can affect mental health.

Clinical and cognitive features associated with psychosis in Parkinson's disease: a longitudinal study

BackgroundParkinson's disease psychosis (PDPsy) is associated with increased nursing home placement and mortality and is closely linked with cognitive dysfunction.ObjectiveAssess the clinical and cognitive features associated with PDPsy in patients without dementia.MethodsWe prospectively recruited people with Parkinson's disease (PwP) without dementia for a 3-year, longitudinal study at an outpatient movement disorders clinic. Participants completed annual visits involving assessment of motor and non-motor symptoms including neuropsychological testing. PDPsy was defined as the recurring presence of visual illusions, sense of presence, hallucinations, or delusions for at least 1 month. Using generalized estimating equations, we conducted two sets of analyses to separately assess the clinical and the cognitive predictors of PDPsy.ResultsWe enrolled 105 participants. At baseline, mean age was 67.8 (SD = 8.0), median disease duration was 4.9 years (IQR: 3.4–7.7), and mean MoCA was 24.8 (SD = 2.3). Prevalence of PDPsy increased over 3 years from 31% (n = 32) to 39% (n = 26). Forty-five participants (43%) experienced PDPsy. Visual illusions were most common (70%, n = 84), followed by hallucinations (58.3%, n = 70). In multivariate analysis, of the clinical variables, only depressive symptoms [OR 1.09, 95% CI: (1.03, 1.16), p = 0.004] increased the odds of PDPsy; of the cognitive variables, only Trail Making Test B-A scores [OR 1.43, 95% CI: (1.06, 1.93), p = 0.018] significantly increased the odds of PDPsy.ConclusionsIn PwP without dementia, depressive symptoms were associated with increased risk of PDPsy. Executive/attentional dysfunction was also associated with PDPsy and may mark the transition from isolated minor hallucinations to more complex psychotic symptoms.

E Pur Si Move! Motion-Based Illusions, Perception and Depiction

ABSTRACT Can static pictures depict motion and temporal properties? This is an open question that is becoming increasingly discussed in both aesthetics and the philosophy of mind. Theorists working on this issue have mainly focused on static pictures of dynamic scenes and streaky images—such as futurists’ paintings or long-exposure photographs. And yet, we could ask: if there is some success in creating an illusory impression of movement in a static image—as is the case in optical illusions of movement, such as Bridget Riley’s Fall (1963: Tate, London), or Kitaoka’s Rotating Snakes Illusion—is this to say that such static images depict movement? As far as I know, no one working on the depiction of motion has specifically and systematically tackled motion-based illusions nor tried to answer this question. This paper considers two cases of optical illusions of movement and concludes that one of them is involved in the depiction of movement. While the declared goal of my analysis is to answer a quite circumscribed question, it is also the occasion to tackle motion-based illusions tout court—to account for the complex visual experiences they elicit and related phenomenology. Moreover, this account has interesting consequences for theorizing depiction and pictorial experience in general. In particular, it constitutes a counterexample to resemblance theories of depiction.

Being, non-being and the in-between

What is presence really? What are we talking about when we talk about presence? For a performer, it seems such an obvious thing but the closer you look, the more elusive it becomes, like one of those optical illusions which can only be perceived sideways through the eyes; looking directly makes it immediately disappear. And the whole thing becomes even more sideways when we take presence and put it in the middle of a classroom. Is it possible that we might have been over emphasising presence in the search for the elusive-mysterious? Have we been overly focused on presence in our pursuit of the qualities that make teaching and learning truly transformative? And obviously, what sort of transformative are we talking about in the fractured times that we live in? What is the other side of the story? What can Absence tell us about its polar twin? Does the absent become present by its very absence? And what or who is it that is absent? In my talk which I've framed as a set of field notes, entirely subjective observations gathered over a period of time, I am drawing upon my experience as a performer in search of the elusive-mysterious; my experience as a teaching artist in a teacher education program at Delhi University; and as a researcher investigating teacher agency in the classroom. In interrogating the binary of presence/absence, I seek to throw some light into that liminal space where these two intersect and collide, and begin to reveal the elusive-mysterious so that pedagogical practices can be reimagined and reenacted.

Teacher: Where are You? About a Scenario for Permanent Teacher Training in Which the Teaching of Geometry is Invited to Think Professionally

In this article we share the story of a proposal for permanent training for mathematics teachers who are in charge of the training of students between 12 and 18 years old. We present a task and the fundamentals that lead us to develop it in this training scenario, for the collective construction of specialized knowledge of those who teach topics related to metric geometry and its relationship with optical illusions. We comment on the planning of the scenario and the results achieved from the perspective of the Mathematics Teacher's Specialized Knowledge Model (MTSK Model), which we relate to studies on the use of technologies in mathematics classrooms. We conclude with an analysis of the strengths and weaknesses, opportunities and threats that may arise in scenarios such as the one described for the permanent training of teachers considered teaching professionals.

Illusions exist in everyday life with natural stimuli: The banana-bisection Illusion.

We report a novel visual illusion that is present in the natural environment. In attempting to cut a banana in half, many people make the side adjacent to the stem shorter, because they see it as longer than it is. This study tested the presence of the banana bisection illusion with outline drawings and a 3D realistic-looking plastic banana. According to Gibson (1966) illusions are the consequence of artificial and impoverished stimuli, such as line drawings. However, the banana bisection illusion was found with naturalistic-looking 3D stimuli. A second experiment with solid 3D plastic bananas found the illusion with and without the stem, but the illusion was larger with the stem present.

Concurrent perception of competing predictions: A "split-stimulus effect".

Visual illusions are systematic misperceptions that can help us glean the heuristics with which the brain constructs visual experience. In a recently discovered visual illusion (the "frame effect"), it has been shown that flashing a stimulus inside of a moving frame produces a large misperception of that stimulus's position. Across two experiments, we investigated a novel illusion (the "split stimulus effect") where the symmetrical motion of two overlaid frames produces two simultaneous positional misperceptions of a single stimulus. That is, one stimulus is presented but two are perceived. In both experiments, a single red dot was flashed when the moving frames reversed direction, and participants were asked to report how many dots they saw. Naïve participants sometimes reported seeing two dots when only one was presented, indicating spontaneous perception of the illusion. A Bayesian analysis of the population prevalence of this effect was conducted. The dependence of this effect on the frames' speed, the dot's opacity, spatial attention, as the presence/absence of pre-flash motion ("postdiction") was also investigated, and the features of this illusion were compared to similar motion position illusions within a predictive processing framework. In demonstrating this illusory "splitting" effect, this study is the first to show that it is possible to be simultaneously aware of two opposing perceptual predictions about a single object and provides evidence of the hyperpriors that limit and inform the structure of visual experience.

Alice in Wonderland syndrome or delirium? a case of a five-year-old girl with hallucinations of snakes

Alice in Wonderland syndrome was first defined by the British psychiatrist John Todd in 1955 as a disorder characterized by episodes of visual illusions, body shape, temporal and spatial distortions. Delirium is a clinical neuropsychiatric disorder showing global encephalopathic dysfunction. In this case, we will present a patient of a 5-year-old girl with the complaint of seeing snakes. Our aim is to help make a differential diagnosis between the two diseases in a patient with similar complaints.

Dazzling damselfish: investigating motion dazzle as a defence strategy in humbug damselfish (Dascyllus aruanus)

Many animals possess high-contrast body patterns. When moving, these patterns may create confusing or conflicting visual cues that affect a predator’s ability to visually target or capture them, a phenomenon called motion dazzle. The dazzle patterns may generate different forms of optical illusion that can mislead observers about the shape, speed, trajectory and range of the animal. Moreover, it is possible that the disruptive visual effects of the high contrast body patterns can be enhanced when moving against a high contrast background. In this study, we used the humbug damselfish (Dascyllus aruanus) to model the apparent motion cues of its high contrast body stripes against high contrast background gratings of different widths and orientations, from the perspective of a predator. We found with higher frequency gratings, when the background is indiscriminable to a viewer, that the humbugs may rely on the confusing motion cues created by internal stripes. With lower frequency gratings, where the background is likely perceivable by a viewer, the humbugs can rely more on confusing motion cues induced by disruption of edges from both the background and body patterning. We also assessed whether humbugs altered their behaviour in response to different backgrounds. Humbugs remained closer and moved less overall in response to backgrounds with a spatial structure similar to their own striped body pattern, possibly to stay camouflaged against the background and thus avoid revealing themselves to potential predators. At backgrounds with higher frequency gratings, humbugs moved more which may represent a greater reliance on the internal contrast of the fish’s striped body pattern to generate motion dazzle. It is possible that the humbug stripes provide multiple protective strategies depending on the context and that the fish may alter their behaviour depending on the background to maximise their protection.

Combined manifestation of two geometric visual illusions.

The present study continued to investigate whether the effects of length misperception caused by cross-shaped (formed by two pairs of the oppositely oriented Müller-Lyer wings) contextual distractors can be explained by the combined manifestation of two different (i.e., the Müller-Lyer and filled-space) geometric illusions of extent. In psychophysical experiments, the luminance of one pair of wings was randomly changed, while the luminance of the other pair remained constant. Two different distractor orientations were used-when the wings with constant luminance formed the right side of the cross or the left side, otherwise. To separately evaluate the manifestation of the Müller-Lyer illusion under different luminance conditions, two distracting crosses of the same orientation were attached to the lateral stimulus terminators in the first series of experiments. In the following four series, a single distracting cross (with different orientation) was attached to one of the lateral stimulus terminators and various combinations of the constant and background luminance were used. To interpret the experimental data, we used the basic computational principles of previously developed quantitative models of hypothetical visual mechanisms underlying the emergence of the Müller-Lyer illusion and the filled-space illusion. It was shown that the results of theoretical calculations adequately approximate the experimental curves obtained for all modifications of stimuli, which strongly supports the suggestion that the joint manifestations of these two illusions can be considered among the main factors determining the features of the illusion investigated.

The Evolution of Simplifying Heuristics in Visual Cognition: Categorization, Specialization, and Visual Illusions.

Animals live in visually complex environments. As a result, visual systems have evolved mechanisms that simplify visual processing and allow animals to focus on the information that is most relevant to adaptive decision making. This review explores two key mechanisms that animals use to efficiently process visual information: categorization and specialization. Categorization occurs when an animal's perceptual system sorts continuously varying stimuli into a set of discrete categories. Specialization occurs when particular classes of stimuli are processed using distinct cognitive operations that are not used for other classes of stimuli. We also describe a nonadaptive consequence of simplifying heuristics: visual illusions, where visual perception consistently misleads the viewer about the state of the external world or objects within it. We take an explicitly comparative approach by exploring similarities and differences in visual cognition across human and nonhuman taxa. Considering areas of convergence and divergence across taxa provides insight into the evolution and function of visual systems and associated perceptual strategies.

Understanding visual perception in visual snow syndrome: a battery of psychophysical tests plus the 30-day clinical diary.

Patients with visual snow syndrome (VSS) experience uncountable flickering tiny dots in the entire visual field. Symptoms often persist over the years. Very little is known about altered perception in VSS. VSS is diagnosed based on subjective reports because there is no manual with objective measures. In this study, 20 patients with VSS and 17 healthy controls performed a battery of tests assessing visual acuity, contrast sensitivity, illusion perception, spatial-temporal vision, motion perception, visual attention, and selective attention. Surprisingly, except for one test, which is the honeycomb illusion, patients performed at the same level as controls. Patients reporting black and white visual snow performed better in the Stroop test compared to patients reporting other visual snow colours. In addition to a clinical visit, the 30-day clinical diary was administered to patients to broadly measure their symptom severity. We found that better performance in the tests, in particular in the contrast and coherent motion tests, was correlated with lower VSS symptoms, weaker VS characteristics (e.g. density and size) and lower VS severity. Our results suggest that, even if visual abilities are not deteriorated by VSS, they can determine how severe symptoms are, and show that VSS is an heterogenous disorder where symptoms and visual abilities vary between patients, for instance depending on the VS colour. The study was primarily designed to identify tests where performance differs between controls and patients. In addition, exploratory analyses were conducted to initiate an understanding of the overall pattern of relationships between patients' visual abilities and symptoms, which is of clinical relevance. Future studies with more power are necessary to validate our findings.

AlterVerse: A Framework for Interactive Virtual Altering of Physical Objects in Extended Reality Environments.

This article presents AlterVerse, a framework that provides users with novel experiences through visual illusions of interactively altering physical objects in extended reality environments. In the AlterVerse framework, physical objects are seamlessly virtualized by aligning their 3-D virtual replicas with them. It enables users to manipulate (move or rotate) and reshape (deform the shapes or transform the styles of) the physical objects virtually. Simultaneously, the physical objects are visually removed from a physical environment, creating the perception that the altering occurs directly on the physical objects. As a promising application of the AlterVerse framework, the article demonstrates interactive virtual altering of home furniture in interior design or decoration scenarios without physically altering existing furniture.

회화작품과의 비교분석을 통한 인디 게임에 있어서의 착시 응용에 대한 연구

The combination of optical illusions and indie games has great potential for artistic expression. Based on optical illusions, this study examines the interaction between players and optical illusions in indie games, and focuses on optical illusions in contemporary indie games, which are compared and analyzed with paintings by artists such as Escher, Andrea Pozzo, Josef Alberts, and Luca Giordano to analyze the formative method that applies optical illusions in indie game art. Based on the development of indie games that use optical illusions formatively, four optical illusions are summarized: optical illusion of contradictory space, active viewpoint transformation of players, subjective visual perception of transformation, and reconstruction of light and shadow. Representative and influential indie games including “Monument Valley,” “Echochrome,” “Watch,” “Trick Art Dungeon,” “Shadowmatic,” “Superliminal,” and “Kubic” were selected and analyzed. As a result of comparing these independent games and artworks, it was concluded that modern optical independent video games should stimulate players' aesthetic cognitive function by properly fusing a simple screen, simple color use, and the complexity of optical space. If the 'circulation' and 'infinite' characteristics of optical illusions are dynamically applied through video games, it can be expected that a new formative art combined with interaction will be born.

Supraspinal Activation Induced by Visual Kinesthetic Illusion Modulates Spinal Excitability.

Repetitive passive movement (RPM) enhances reciprocal inhibition. RPM is more effective when performed rapidly and at wide joint angles. However, patients with limited joint range of motion may not receive the most effective RPM. Therefore, having an alternative method for performing RPM in patients who cannot perform actual exercise due to limited joint motion is necessary. This study investigated the effects of RPM on spinal excitability using a visual kinesthetic illusion. Participants included 17 healthy adults (7 women). Measurements were taken before, during, and immediately after the intervention. We established two intervention conditions: the control condition, in which participants focused their attention forward, and the illusion condition, in which participants watched a video about RPM. F-waves from the tibialis anterior and soleus muscles were measured, and F-wave persistence and F/M amplitude ratios were analyzed. Under the illusion condition, compared with the preintervention condition, the F/M amplitude ratio of the tibialis anterior increased by approximately 44% during the intervention (p < 0.05), whereas the F-wave persistence of the soleus decreased by approximately 23% from the immediate start of the intervention (p < 0.05). This study suggests that a visual kinesthetic illusion can increase the spinal excitability of the tibialis anterior, whereas reciprocal inhibition can decrease the spinal excitability of the soleus.

Quantum-tunneling deep neural network for optical illusion recognition

The discovery of the quantum tunneling (QT) effect—the transmission of particles through a high potential barrier—was one of the most impressive achievements of quantum mechanics made in the 1920s. Responding to the contemporary challenges, I introduce a deep neural network (DNN) architecture that processes information using the effect of QT. I demonstrate the ability of QT-DNN to recognize optical illusions like a human. Tasking QT-DNN to simulate human perception of the Necker cube and Rubin’s vase, I provide arguments in favor of the superiority of QT-based activation functions over the activation functions optimized for modern applications in machine vision, also showing that, at the fundamental level, QT-DNN is closely related to biology-inspired DNNs and models based on the principles of quantum information processing.

Effect of expressway exit deceleration markings on distracted drivers in China

Expressway exit areas experience traffic diversion and complex road conditions, making them accident-prone areas. In this study, transverse and fishbone visual illusion deceleration markings were selected to optimize the induction facilities at expressway exits. The research aims to investigate the impact of these markings on the driving behavior, cognitive load, and physiological characteristics of drivers in various distracted scenarios at expressway exit areas. Furthermore, a comprehensive evaluation of each experimental scheme is conducted using the Matter-Element Extension Model. The study found that the implementation of deceleration markings can effectively enhance driver alertness and lane change awareness, enabling drivers to reduce their speed to near the speed limit in exit areas without compromising driving comfort. Compared to the situation without markings, drivers begin to decelerate approximately 600 m earlier and exit the ramp when markings are present. Fishbone deceleration markings, in contrast to transverse markings, result in lower vehicle speeds, smoother deceleration, and more effectively stimulate drivers' intention to change lanes, guiding them to make the final lane change earlier. Based on the comprehensive evaluation results, it is recommended that transverse or fishbone deceleration markings be considered in engineering practice. These markings have not produced significant effects on driver visual fatigue and driving load, with fishbone markings demonstrating superior comprehensive evaluation outcomes. These research findings can provide valuable insights for future expressway exit area marking design schemes, further enhancing driver safety.

Visual Illusion Created by a Striped Pattern Through Augmented Reality for the Prevention of Tumbling on Stairs.

A fall on stairs can be a dangerous accident. An important indicator of falling risk is the foot clearance, which is the height of the foot when ascending stairs or the distance of the foot from the step when descending. We developed an augmented reality system with a holographic lens using a visual illusion to improve the foot clearance on stairs. The system draws a vertical striped pattern on the stair riser as the participant ascends the stairs to create the illusion that the steps are higher than the actual steps, and draws a horizontal striped pattern on the stair tread as the participant descends the stairs to create the illusion of narrower stairs. We experimentally evaluated the accuracy of the system and fitted a model to determine the appropriate stripe thickness. Finally, participants ascended and descended stairs before, during, and after using the augmented reality system. The foot clearance significantly improved, not only while the participants used the system but also after they used the system compared with before.

Influence of global/local processing on perceived colour transparency.

Our cognitive processing is flexible and affected by global/local dominance in prior cognitive tasks. Similar to cognitive processing, perceptual processing, especially colour perception related to global/local processing, may be affected by prior global/local dominance; however, this possibility has not yet been assessed. Here, we examined whether prior tasks involving global/local processing influenced colour perception related to global/local processing. As colour perception is related to global/local processing, we focused on perceived colour transparency, in which a transparent layer is perceived in front of a background layer, even though these stimuli are physically in the same layer. When viewing the colour transparency stimulus, we expected that the perceived colour of a specific region, when focusing on only the local region, would differ from that when focusing on the whole image. In our study, the participants completed a global or local Navon task, followed by a colour-matching task that assessed how they saw colours using colour transparency stimuli. The degree of optical illusion (i.e., perceived colour transparency) after the global Navon task was greater than that after the local Navon task. Thus, prior global/local processing, a flexible mode of cognitive processing, influenced colour perception. This study provides new insight into perceptual flexibility, especially in colour perception.

How to reward animals based on their subjective percepts: A Bayesian approach to online estimation of perceptual biases.

Elucidating the neural basis of perceptual biases, such as those produced by visual illusions, can provide powerful insights into the neural mechanisms of perceptual inference. However, studying the subjective percepts of animals poses a fundamental challenge: unlike human participants, animals cannot be verbally instructed to report what they see, hear, or feel. Instead, they must be trained to perform a task for reward, and researchers must infer from their responses what the animal perceived. However, animals' responses are shaped by reward feedback, thus raising the major concern that the reward regimen may alter the animal's decision strategy or even intrinsic perceptual biases. We developed a method that estimates perceptual bias during task performance and then computes the reward for each trial based on the evolving estimate of the animal's perceptual bias. Our approach makes use of multiple stimulus contexts to dissociate perceptual biases from decision-related biases. Starting with an informative prior, our Bayesian method updates a posterior over the perceptual bias after each trial. The prior can be specified based on data from past sessions, thus reducing the variability of the online estimates and allowing it to converge to a stable estimate over a small number of trials. After validating our method on synthetic data, we apply it to estimate perceptual biases of monkeys in a motion direction discrimination task in which varying background optic flow induces robust perceptual biases. This method overcomes an important challenge to understanding the neural basis of subjective percepts.