Illusion Research Articles

A Taxonomy of Embodiment in the AI Era

This paper presents a taxonomy of agents’ embodiment in physical and virtual environments. It categorizes embodiment based on five entities: the agent being embodied, the possible mediator of the embodiment, the environment in which sensing and acting take place, the degree of body, and the intertwining of body, mind, and environment. The taxonomy is applied to a wide range of embodiment of humans, artifacts, and programs, including recent technological and scientific innovations related to virtual reality, augmented reality, telepresence, the metaverse, digital twins, and large language models. The presented taxonomy is a powerful tool to analyze, clarify, and compare complex cases of embodiment. For example, it makes the choice between a dualistic and non-dualistic perspective of an agent’s embodiment explicit and clear. The taxonomy also aided us to formulate the term “embodiment by proxy” to denote how seemingly non-embodied agents may affect the world by using humans as “extended arms”. We also introduce the concept “off-line embodiment” to describe large language models’ ability to create an illusion of human perception.

Motion-induced blindness shows spatial anisotropies in conscious perception.

Polar angle asymmetries (PAAs), the differences in perceptual experiences and performance across different regions of the visual field are present in various paradigms and tasks of visual perception. Currently, research in this area is sparse, particularly regarding the influence of PAAs during perceptual illusions, highlighting a gap in visual cognition studies. We aim to fill this gap by measuring PAAs across the visual field during an illusion applied to test conscious vision widely. Motion-induced blindness (MIB) is an illusion when a peripheral target disappears from consciousness as the result of a continuously moving background pattern. During MIB we separately measured the average disappearance time of peripheral targets in eight equidistant visual field positions. Our results indicate a significant variation in MIB disappearance times and frequencies as a function of target location. Specifically, we found shorter and fewer disappearances along the cardinal compared to oblique directions, and along the horizontal compared to the vertical meridian. Our results suggest specific consistencies between visual field asymmetries and conscious visual perception.

Illusion of control or passive superstition? A comparison of two explanations for irrational gambling beliefs.

The "illusion of control" is a dominant cognitive illusion in disordered gambling, but its role in shaping irrational gambling beliefs has been questioned by recent null experimental findings. Here, we aimed to test this recent work, in a preregistered Bayesian framework, by additionally correlating the dependent variable (nonuniform probabilistic beliefs) with self-reported gambling behavior and by exploring "passive superstition" as an alternative driver of these irrational gambling beliefs. A between-participants online experiment involving three boxes, one of which a $1 prize was randomly assigned to (N = 3,064; 49.1% males, 49.5% females, 1.4% other; Mage = 42.5 years). Participants estimated the likelihood of each box winning, with any estimates outside the 33%-34% interval categorized as irrational "nonuniform" probabilistic beliefs. "Preselection" participants gave estimates prior to box selection, "post-no-choice" participants had their box randomly selected, and participants in the treatment "postchoice" condition selected their own box. Whether participants gambled within the past 12 months (gambling status), Problem Gambling Severity Index (PGSI) score, and passive superstition scores were used as additional predictors. Comparing postchoice participants with post-no-choice participants (95% CI [0.80, 1.22]) and comparing postchoice with preselection participants (95% CI [0.88, 1.34]) yielded substantial support for a null effect. Gambling status supported substantial evidence for a null effect (95% CI [0.92, 1.30]), whereas higher PGSI (95% CI [1.08, 1.13]) and higher passive superstition scores (95% CI [1.08, 1.10]) overwhelmingly predicted our outcome. Active choice elements in illusions of control may have been overemphasized in irrational gambling beliefs compared to passive superstitions. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Assessing Individual Sensitivity to the Thermal Grill Illusion: A Two-Dimensional Adaptive Psychophysical Approach

In the thermal grill illusion (TGI), the spatial alternation of non-noxious warm and cool temperatures elicits burning sensations that resemble the presence of noxious stimuli. Previous research has largely relied on the use of specific temperature values (i.e., 20°C and 40°C) to study this phenomenon in both healthy individuals and patient populations. However, this methodology fails to account for inter-individual differences in thermal sensitivity, limiting the precision with which TGI responses can be evaluated across diverse populations. To address this gap, we created a Two-Dimensional Thermal Grill Calibration (2D-TGC) protocol, enabling an efficient and precise estimation of the combinations of warm and cool temperatures needed to elicit burning sensations tailored to each individual. By applying the 2D-TGC protocol in 43 healthy participants, we demonstrated key findings: (1) The TGI can be thresholded using an adaptive psychophysical method. (2) Multiple combinations of warm and cool temperatures can elicit this phenomenon. (3) The protocol facilitated the identification of temperature combinations that elicit TGI with varying levels of probability, intensity, and perceived quality ranging from freezing cold to burning hot. (4) TGI responsivity can be quantified as a continuous variable, moving beyond the conventional classification of individuals as responders vs. non-responders based on arbitrary temperature values in the innocuous temperature range. The 2D-TGC offers a comprehensive approach to investigate the TGI across populations with altered thermal sensitivity, and can be integrated with other methods (e.g., neuroimaging) to elucidate the mechanisms responsible for perceptual illusions in the thermo-nociceptive system. PerspectiveThis study reveals that the Thermal Grill Illusion can be accurately measured using psychophysical methods. The innovative Two-Dimensional Thermal Grill Calibration protocol allows for personalized temperature assessments, enhancing our understanding of thermal sensitivity variations and perceptual illusions in the thermo-nociceptive system across different populations.

A new perspective on Misbeliefs: A computational model for perceived control

The discovery of various cognitive biases and social illusions indicates that people routinely have misbeliefs. Focusing on the illusion of control (IOC), this article argues that when time and cognitive resources are limited, and information is imperfect, misbeliefs can be generated naturally in a normal belief formation system, and these misbeliefs might help people adapt better to the environment.In this study, we present a computational model—the informativeness-weighting model (IWM)—describing how beliefs are revised by observed evidence. To be precise, IOC is the result of distinct types of evidence being endowed with different weights according to its informativeness in a belief revision process. To evaluate the model, we also designed two behavioral experiments to compare people’s sense of control with that predicted by the model.In both experiments, our model outperformed two alternative models in predicting and explaining the misestimation of people’s perceived control. Thus, we suggest that our model reflects an adaptive strategy for information processing, which helps to explain why misbeliefs, like IOC, are prevalent in human cognition.

Quantum logic automata generate class IV-like patterns and [formula omitted] noise

Owing to recent advancements in brain science and AI, researchers tend to focus on the concept of self-organized criticality or the edge of chaos. On the other hand, quantum cognition, which is rooted in quantum mechanics, is promising for resolving various cognitive illusions. However, until recently, no connection between criticality and quantum mechanics was proposed. Gunji et al. (2024) recently introduced a linkage termed quantum logic automata, which encompasses not only quantum logic but also criticality characterized by power-law distributions. While quantum logic automata can be derived from various structures, only one of them has been proposed and discussed. Here, we define another type of quantum logic automata involving quantum logic and demonstrate that symmetric quantum logic automata lead to complex Class IV-like patterns and power-law distributions. Our findings support the association between criticality and quantum theory.

When visual attention is divided in the flash-lag effect.

The flash-lag effect (FLE) occurs when a flash's position seems to be delayed relative to a continuously moving object, even though both are physically aligned. Although several studies have demonstrated that reduced attention increases FLE magnitude, the precise mechanism underlying these attention-dependent effects remains elusive. In this study, we investigated the influence of visual attention on the FLE by manipulating the level of attention allocated to multiple stimuli moving simultaneously in different locations. Participants were cued to either focus on one moving stimulus or split their attention among two, three, or four moving stimuli presented in different quadrants. We measured trial-wise FLE to explore potential changes in the magnitude of perceived displacement and its trial-to-trial variability under different attention conditions. Our results reveal that FLE magnitudes were significantly greater when attention was divided among multiple stimuli compared with when attention was focused on a single stimulus, suggesting that divided attention considerably augments the perceptual illusion. However, FLE variability, measured as the coefficient of variation, did not differ between conditions, indicating that the consistency of the illusion is unaffected by divided attention. We discuss the interpretations and implications of our findings in the context of widely accepted explanations of the FLE within a dynamic environment.

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.

An Unavoidable Mind-Set Reversal: Consciousness in Vision Science.

In recent decades, the debate on consciousness has been conditioned by the idea of bottom-up emergence, which has influenced scientific research and raised a few obstacles to any attempt to bridge the explanatory gap. The analysis and explanation of vision conducted according to the accredited methodologies of scientific research in terms of physical stimuli, objectivity, methods, and explanation has encountered the resistance of subjective experience. Moreover, original Gestalt research into vision has generally been merged with cognitive neuroscience. Experimental phenomenology, building on the legacy of Gestalt psychology, has obtained new results in the fields of amodal contours and color stratifications, light perception, figurality, space, so-called perceptual illusions, and subjective space and time. Notwithstanding the outcomes and the impulse given to neuroscientific analyses, the research carried out around these phenomena has never directly confronted the issue of what it means to be conscious or, in other words, the nature of consciousness as self-referentiality. Research has tended to focus on the percept. Therefore, explaining the non-detachability of parts in subjective experience risks becoming a sort of impossible achievement, similar to that of Baron Munchausen, who succeeds in escaping unharmed from this quicksand by pulling himself out by his hair. This paper addresses how to analyze seeing as an undivided whole by discussing several basic dimensions of phenomenal consciousness on an experimental basis and suggesting an alternative way of escaping this quicksand. This mind-set reversal also sheds light on the organization and dependence relationships between phenomenology, psychophysics, and neuroscience.

Consciousness in non-REM-parasomnia episodes.

Sleepwalking and related parasomnias are thought to result from incomplete awakenings out of non-rapid eye movement (non-REM) sleep. Non-REM parasomnia behaviours have been described as unconscious and automatic, or related to vivid, dream-like conscious experiences. Similarly, some observations have suggested that patients are unresponsive during episodes, while others that they can interact with their surroundings. To better grasp and characterise the full spectrum of consciousness and environmental (dis)connection associated with behavioural episodes, 35 adult patients with non-REM sleep parasomnias were interviewed in-depth about their experiences. The level of consciousness during parasomnia episodes was reported to be variable both within and between individuals, ranging from minimal or absent consciousness and largely automatic behaviours (frequently/always present in 36% of patients) to preserved conscious experiences characterised by delusional thinking to varying degrees of specificity (65%), often about impending danger, variably formed, uni- or multisensory hallucinations (53%), impaired insight (77%), negative emotions (75%), and variable, but often pronounced, amnesia (30%). Patients described their experiences as a dream scene during which they felt awake ("awake dreaming"). The surroundings were either realistically perceived, misinterpreted (in the form of perceptual illusions or misidentifications of people), or entirely hallucinated as a function of the prevailing delusion. These observations suggest that the level of consciousness, amnesiaand sensory disconnection during non-REM parasomnia episodes is variable and graded. In their full-fledged expression, non-REM parasomnia experiences feature several core features of dreams. They therefore represent a valuable model for the study of consciousness, sleep-related sensory disconnection and dreaming.

Age-related changes in the susceptibility to visual illusions of size

As the global population ages, understanding of the effect of aging on visual perception is of growing importance. This study investigates age-related changes in adulthood along size perception through the lens of three visual illusions: the Ponzo, Ebbinghaus, and Height-width illusions. Utilizing the Bayesian conceptualization of the aging brain, which posits increased reliance on prior knowledge with age, we explored potential differences in the susceptibility to visual illusions across different age groups in adults (ages 20–85 years). To this end, we used the BTPI (Ben-Gurion University Test for Perceptual Illusions), an online validated battery of visual illusions developed in our lab. The findings revealed distinct patterns of age-related changes for each of the illusions, challenging the idea of a generalized increase in reliance on prior knowledge with age. Specifically, we observed a systematic reduction in susceptibility to the Ebbinghaus illusion with age, while susceptibility to the Height-width illusion increased with age. As for the Ponzo illusion, there were no significant changes with age. These results underscore the complexity of age-related changes in visual perception and converge with previous findings to support the idea that different visual illusions of size are mediated by distinct perceptual mechanisms.

Beyond musical training: Individual influences on the perception of the speech-to-song illusion

When a spoken phrase is repeated several times, listeners often report a perceptual illusion during which speech is transformed into song. The speech-to-song (STS) illusion is often attributed to prosodic elements of speech, though listeners can vary greatly in their STS experience. While previous research established robust links between music aptitude and STS, the present study asks whether other cognitive traits may also influence STS. Individual (in)sensitivity to nonverbal aspects of speech, specifically speech prosody, has been previously linked to autistic traits and emotional intelligence. We test whether the presence of autistic traits, the level of emotional intelligence and musical training, as well as syntactic complexity influence the likelihood, speed, and strength of STS among native British English listeners. The results provide evidence for the involvement of some but not all studied traits. We found sentence complexity to be interacting with a composite score of musical training, and emotional intelligence for the likelihood of STS, whereas sentence complexity influenced the strength of the transformation. These results suggest that individual listener variability may interact with the linguistic parameters of sentences in STS. Crucially, sensitivity to prosody through emotional intelligence or by the presence of autistic traits does not mediate the transformation.

Presence, (re)focused and explicated

ABSTRACT This paper offers a revised conceptualization and categorization of presence, building upon Kwan Min Lee’s framework and reviewing related scholarships. The proposed approach emphasizes the afforded virtual experiences rather than the specific technologies and centers around a core definition of “presence” as the perceptual illusion of non-simulation and/or non-mediation. This revised framework encompasses a wide range of media technologies that reproduce activities, entities, or environments, excluding media narratives. By refining the understanding of presence, this paper aims to provide a more precise comprehension of the concept, its contributing factors, measurements, and the associated outcomes.

Education amid the deluge of enhancement discourses

This article delves into the examination of the similarities and disparities between education and enhancement, with a particular focus on enhancement within the realm of NBIC (Nano-Bio-Information Technology, Cognitive Science). After scrutinizing how proponents of enhancement have delineated the concept of education, our investigation unfolds along two primary dimensions: the anthropological underpinnings of education and enhancement discourse and their respective objectives. Through this analysis, we assert that education and enhancement exhibit distinct characteristics and objectives, defying easy comparison for determining which approach is more conducive to human improvement, notwithstanding their superficially analogous theoretical frameworks and objectives. Furthermore, we aim to highlight the perceptual illusions that blur the demarcation lines between education and enhancement, in order to establish a clear and distinctive role for education amid the plethora of enhancement discourses.

Response to geometrical visual illusions in non-human animals: a meta-analysis.

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.

Perception of optical illusions in ungulates: insights from goats, sheep, guanacos and llamas

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.

The fusion point of temporal binding: Promises and perils of multisensory accounts

Performing an action to initiate a consequence in the environment triggers the perceptual illusion of temporal binding. This phenomenon entails that actions and following effects are perceived to occur closer in time than they do outside the action-effect relationship. Here we ask whether temporal binding can be explained in terms of multisensory integration, by assuming either multisensory fusion or partial integration of the two events. We gathered two datasets featuring a wide range of action-effect delays as a key factor influencing integration. We then tested the fit of a computational model for multisensory integration, the statistically optimal cue integration (SOCI) model. Indeed, qualitative aspects of the data on a group-level followed the principles of a multisensory account. By contrast, quantitative evidence from a comprehensive model evaluation indicated that temporal binding cannot be reduced to multisensory integration. Rather, multisensory integration should be seen as one of several component processes underlying temporal binding on an individual level.

Deep Learning Based Lipreading for Video Captioning

Visual speech recognition, often referred to as lipreading, has garnered significant attention in recent years due to its potential applications in various fields such as human-computer interaction, accessibility technology, and biometric security systems. This paper explores the challenges and advancements in the field of lipreading, which involves deciphering speech from visual cues, primarily movements of the lips, tongue, and teeth. Despite being an essential aspect of human communication, lipreading presents inherent difficulties, especially in noisy environments or when contextual information is limited. The McGurk effect, where conflicting audio and visual cues lead to perceptual illusions, highlights the complexity of lipreading. Human lipreading performance varies widely, with hearing-impaired individuals achieving relatively low accuracy rates. Automating lipreading using machine learning techniques has emerged as a promising solution, with potential applications ranging from silent dictation in public spaces to biometric authentication systems. Visual speech recognition methods can be broadly categorized into those that focus on mimicking words and those that model visemes, visually distinguishable phonemes. While word-based approaches are suitable for isolated word recognition, viseme-based techniques are better suited for continuous speech recognition tasks. This study proposes a novel deep learning architecture for lipreading, leveraging Conv3D layers for spatiotemporal feature extraction and bidirectional LSTM layers for sequence modelling. The proposed model demonstrates significant improvements in lipreading accuracy, outperforming traditional methods on benchmark datasets. The practical implications of automated lipreading extend beyond accessibility technology to include biometric identity verification, security surveillance, and enhanced communication aids for individuals with hearing impairments. This paper provides insights into the advancements, challenges, and future directions of visual speech recognition research, paving the way for innovative applications in diverse domains.

Video mirror feedback induces more extensive brain activation compared to the mirror box: an fNIRS study in healthy adults

BackgroundMirror therapy (MT) has been shown to be effective for motor recovery of the upper limb after a stroke. The cerebral mechanisms of mirror therapy involve the precuneus, premotor cortex and primary motor cortex. Activation of the precuneus could be a marker of this effectiveness. MT has some limitations and video therapy (VT) tools are being developed to optimise MT. While the clinical superiority of these new tools remains to be demonstrated, comparing the cerebral mechanisms of these different modalities will provide a better understanding of the related neuroplasticity mechanisms.MethodsThirty-three right-handed healthy individuals were included in this study. Participants were equipped with a near-infrared spectroscopy headset covering the precuneus, the premotor cortex and the primary motor cortex of each hemisphere. Each participant performed 3 tasks: a MT task (right hand movement and left visual feedback), a VT task (left visual feedback only) and a control task (right hand movement only). Perception of illusion was rated for MT and VT by asking participants to rate the intensity using a visual analogue scale. The aim of this study was to compare brain activation during MT and VT. We also evaluated the correlation between the precuneus activation and the illusion quality of the visual mirrored feedback.ResultsWe found a greater activation of the precuneus contralateral to the visual feedback during VT than during MT. We also showed that activation of primary motor cortex and premotor cortex contralateral to visual feedback was more extensive in VT than in MT. Illusion perception was not correlated with precuneus activation.ConclusionVT led to greater activation of a parieto-frontal network than MT. This could result from a greater focus on visual feedback and a reduction in interhemispheric inhibition in VT because of the absence of an associated motor task. These results suggest that VT could promote neuroplasticity mechanisms in people with brain lesions more efficiently than MT.Clinical trial registrationNCT04738851.

Measuring virtual embodiment: A psychometric investigation of a standardised questionnaire for the psychological sciences

Psychological science increasingly employs virtual reality (VR) as a therapeutic and experimental tool. When represented by an avatar, a user's self-perception is altered through a full-body perceptual illusion known as virtual embodiment. However, inconsistent measurement of this construct derives uncertainties about the efficacy of VR-driven behavioural, cognitive, and social-psychological changes. Accordingly, we sought to provide psychological scientists a valid and reliable measure to assess the virtual embodiment construct during experimental and therapeutic simulations. In a repeated-measures experimental paradigm, participants (N = 86) completed a series of visuo-motor tasks in-vivo and in VR. Our study had three objectives: 1) compare visuo-motor performance across in-vivo and VR tasks; 2) assess the psychometric properties of theoretically foundational body ownership, agency, and self-location dimensions from a virtual embodiment questionnaire widely used in the literature; 3) analyse the simplified 11-item questionnaire's underlying structure using principal component analysis (PCA). We found that VR embodiment does not directly align with physical embodiment when considering proprioception and kinaesthesia, and there is limited support for convergent and discriminant validity of body ownership, agency, and self-location as independent dimensions of the embodiment construct. However, there is strong support for criterion validity when these dimensions comprise the overall measurement of embodiment. The PCA revealed a straightforward and theoretically interpretable underlying structure with three components: embodiment, disembodiment, and agency. This study offers psychometric support for the exploration of the simplified 11-item questionnaire as a theoretically grounded measure for behavioural scientists who seek to investigate virtual embodiment as a psychological construct.