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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.

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The illusion of control refers to a behavioral bias in which people believe they have greater control over completely stochastic events than they actually do, leading to an inflated estimate of reward probability than objective probability warrants. In this study, we examined how reward system is modulated by the illusion of control through the lens of neural dynamics. Participants in a behavioral task exhibited a classical illusion of control, assigning a higher value to the gambling wheels they picked themselves than to those given randomly. An event-related potential study of the same task revealed that this behavioral bias is associated with reduced reward anticipation as indexed by the stimulus-preceding negativity, diminished positive prediction error signals as reflected by the reward positivity, and enhanced motivational salience as revealed by the P300. Our findings offer a mechanistic understanding of the illusion of control in terms of reward dynamics.

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Background Visual-motor illusion (VMI) is a cognitive approach used to evoke kinesthetic sensations. Research suggests that VMI can modulate brain activity depending on the specific joint movement observed. This study aimed to identify differences in brain activity when observing video images of joint movements at different intensities of movement in VMI. Methodology The study included 14 healthy adult participants. Two types of video images were used: pure ankle dorsiflexion movements (Standard-VMI) and ankle dorsiflexion movements with added resistance (Power-VMI). The brain activity measurement protocol employed a block design with one set of 15 seconds rest, 30 seconds VMI task, and 30 seconds follow-up. Each participant performed the VMI task twice, alternating between Standard-VMI and Power-VMI. Brain activity was measured using functional near-infrared spectroscopy, focusing on motor-related regions. Subjective impressions were assessed using visual analog scales (VAS) for kinesthetic illusions. Results The results revealed that Power-VMI stimulated significantly greater brain activity in the premotor and supplementary motor cortex, supramarginal gyrus, and superior parietal lobule compared with Standard-VMI. Power-VMI resulted in higher VAS values for kinesthetic illusion than Standard-VMI. Additionally, a positive correlation was observed between brain activity in the superior parietal lobule and the degree of kinesthetic illusion. Conclusions These findings indicate that Power-VMI enhances both motor-related brain areas and motor-sensory illusions, potentially having a greater impact on improving motor function. This study provides valuable insights for developing VMI interventions for rehabilitation, particularly for individuals with paralysis or movement impairments.

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The rubber hand illusion involves the sense of body ownership of a fake hand. We showed that concurrent visuotactile stimuli to unilateral rubber and real hands can induce the embodiment of bilateral rubber hands when both rubber hands are positioned on the table. This phenomenon indicates that the brain has an integrated representation of the sense of body ownership for both hands.

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A simple button press towards a prime stimulus enhances subsequent visual search for objects that match the prime. The present study investigated whether this action effect is a general phenomenon across different task domains, and the underlying neural mechanisms. The action effect was measured in an unspeeded size-matching task, with the presentation of the central target and the surrounding inducers of the Ebbinghaus illusion together to one eye or separately to each eye, and when repetitive TMS was applied over right primary motor cortex (M1). The results showed that a prior key-press significantly reduced the illusion effect compared to passive viewing. Notably, the action effect persisted with dichoptic presentation of the Ebbinghaus configuration, but disappeared with the right M1 disruption. These results suggest that action guides visual perception to influence human behavior, which mainly affects the late visual processing stage and probably relies on feedback projections from the motor cortex.

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People are often overconfident about their ability to explain how everyday phenomena and artifacts work (devices, natural processes, historical events, etc.). However, the metacognitive mechanisms involved in this bias have not been fully elucidated. The aim of this study was to establish whether the ability to perform deliberate and analytic processes moderates the effect of informational cues such as the social desirability of knowledge on the Illusion of Explanatory Depth (IOED). To this purpose, the participants' cognitive load was manipulated as they provided initial estimates of causal understanding of national historical events in the standard IOED paradigm. The results showed that neither the social desirability of specific causal knowledge nor the cognitive load manipulations had direct effects on the IOED. However, subsequent exploratory analyses indicated that high cognitive load was related to lower performance on concurrent memory tasks, which in turn was associated with a higher IOED magnitude. Higher analytical processing was also related to lower IOED. Implications for both dual-process models of metacognition and the design of task environments that help to reduce this bias are discussed.

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Virtual Reality has significantly improved the understanding of body experience, through techniques such as Body Illusion. Body Illusion allows individuals to perceive an artificial body as their own, changing body perceptual and affective components. Prior research has predominantly focused on female participants, leaving the impact of Body Illusion on males less understood. This study seeks to fill this gap by examining the nuanced bodily experiences of men in comparison to women. 40 participants (20 females and 20 males) were proposed with visuo-tactile synchronous and asynchronous Body Illusion to explore changes in body satisfaction and body size estimation across three critical areas: shoulders, hips, and waist. Results revealed significant initial disparities, with females displaying greater body dissatisfaction and a tendency to overestimate body size. After Body Illusion, females adjusted the hips perceived body size closer to that of the virtual body and reported increased body satisfaction independent of the condition. Conversely, males showed changes only in waist size estimation only after synchronous stimulation without significant shifts in body satisfaction. These results suggest a higher sensitivity of women to embodied experiences, potentially due to societal influences and a greater inclination towards self-objectification. These insights pave the way for creating more refined and effective interventions for body image issues, highlighting the importance of incorporating gender-specific considerations in VR-based prevention and therapeutical programs.

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The Ames room illusion is one of the best-known geometrical illusions but its geometrical properties are often misunderstood. This study discusses the differences in the geometrical properties between the original Ames room and what have been often referred to as "Ames rooms" in recent studies.

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INTRODUCTION: Subjective cognitive decline (SCD) refers to individuals' perceived decline in memory and/or other cognitive abilities relative to their previous level of performance. Sensory decline is one of the main manifestations of decline in older adults with SCD. The efficient integration of visual and auditory information, known as audiovisual integration, is a crucial perceptual process. This study aims to evaluate audiovisual integration in older adults with SCD. METHODS: We adopted the audiovisual detection task, the Colavita task, and the Sound-Induced Flash Illusion (SIFI) task to evaluate the audiovisual integration by examining both redundant and illusory effects. Older adults diagnosed with SCD (N = 50, mean age = 67.8 years) and a control group of non-SCD older adults (N = 51, mean age = 66.5 years) were recruited. All participants took part in the three aforementioned experiments. RESULTS: The outcomes showed that a redundant effect occurred in both SCD and non-SCD older adults, with SCD older adults gaining more benefits in audiovisual detection task. Moreover, an equivalent amount of the visual dominance effect was observed among both SCD and non-SCD older adults in Colavita task. In addition, older adults with SCD perceived an equal fission illusion but a bigger fusion illusion compared with non-SCD older adults in SIFI task. CONCLUSIONS: Overall, older adults with SCD exhibit increased audiovisual redundant effects and stronger fusion illusion susceptibility compared to non-SCD older adults. Besides, visual dominance was observed in both groups via the Colavita task, with no significant difference between non-SCD and SCD older adults. These findings implied that audiovisual integration might offer a potential way for the identification of SCD.

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The classical body ownership illusion, such as the rubber hand illusion, is achieved through appropriate proprioceptive displacement within temporal and spatial constraints that do not exceed the limits of proprioceptive flexibility. In the 2023 Best Illusion of the Year Contest, we introduced Buddha's ear illusion (BEI), which creates the illusion of owning a dramatically deformed earlobe through immediate visuotactile stimulation and seemingly challenges classical proprioceptive boundaries. The laboratory experiment examined the mechanics of this illusion, revealing a significant interaction between tactile earlobe pulling and visual miming that contributed to the enhanced perception of earlobe stretch. Importantly, 88% of the participants confirmed the illusory earlobe stretch (a rating of +4 or higher on a 7-point scale). More than half reported an earlobe descent of >10 cm within a 10-s visuotactile stimulation. The findings suggest that BEI operates on a distinct principle separate from proprioceptive modulation in contrast to classical ownership illusions.

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In behavioral sciences, there is growing concern about the inflation of false-positive rates due to the amount of under-powered studies that have been shared in the past years. While problematic, having the possibility to recruit (lots of) participants (for a lot of time) is realistically not achievable for many research facilities. Factors that hinder the reaching of optimal sample sizes are, to name but a few, research costs, participants' availability and commitment, and logistics. We challenge these issues by introducing PsySuite, an Android app designed to foster a remote approach to multimodal behavioral testing. To validate PsySuite, we first evaluated its ability to generate stimuli appropriate to rigorous psychophysical testing, measuring both the app's accuracy (i.e., stimuli's onset, offset, and multimodal simultaneity) and precision (i.e., the stability of a given pattern across trials), using two different smartphone models. We then evaluated PsySuite's ability to replicate perceptual performances obtained using a classic psychophysical paradigm, comparing sample data collected with the app against those measured via a PC-based setup. Our results showed that PsySuite could accurately reproduce stimuli with a minimum duration of 7 ms, 17 ms, and 30 ms for the auditory, visual, and tactile modalities, respectively, and that perceptual performances obtained with PsySuite were consistent with the perceptual behavior observed using the classical setup. Combined with the high accessibility inherently supported by PsySuite, here we ought to share the app to further boost psychophysical research, aiming at setting it to a cheap, user-friendly, and portable level.

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Causal illusions consist of believing that there is a causal relationship between events that are actually unrelated. This bias is associated with pseudoscience, stereotypes and other unjustified beliefs. Thus, it seems important to develop educational interventions to reduce them. To our knowledge, the only debiasing intervention designed to be used at schools was developed by Barberia et al. (Barberia et al. 2013 PLoS One 8, e71303 (doi:10.1371/journal.pone.0071303)), focusing on base rates, control conditions and confounding variables. Their assessment used an active causal illusion task where participants could manipulate the candidate cause. The intervention reduced causal illusions in adolescents but was only tested in a small experimental project. The present research evaluated it in a large-scale project through a collaboration with the Spanish Foundation for Science and Technology (FECYT), and was conducted in schools to make it ecologically valid. It included a pilot study (n = 287), a large-scale implementation (n = 1668; 40 schools) and a six-month follow-up (n = 353). Results showed medium-to-large and long-lasting effects on the reduction of causal illusions. To our knowledge, this is the first research showing the efficacy and long-term effects of a debiasing intervention against causal illusions that can be used on a large scale through the educational system.

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Virtual reality (VR)-guided motor imagery (MI) is a widely used approach for motor rehabilitation, especially for patients with severe motor impairments. Most approaches provide visual guidance from the first-person perspective (1PP). MI training with visual guidance from the third-person perspective (3PP) remains largely unexplored. We argue that 3PP MI training has its own advantages and can supplement 1PP MI. For some movements beyond the view of 1PP, such as shoulder shrugging and other axial movements, MI are suitable performed under 3PP. However, the efficiency of existing paradigms for 3PP MI is unsatisfactory. We speculate that the absence of sense of body ownership (SOO) from 3PP could be one possible factor and hypothesize that 3PP MI could be enhanced by eliciting SOO over a 3PP avatar. Based on our hypothesis, a novel paradigm was proposed to enhance 3PP MI by inducing full-body illusion (FBI) from 3PP, which is similar to the so-called out-of-body experience (OBE), using synchronous visuo-tactile stimulus with VR. The event-related Electroencephalograph (EEG) desynchronization (ERD) at motor-related regions from 31 healthy participants were calculated and compared with a control paradigm without "OBE" FBI induction. This study attempts to enhance 3PP MI with FBI induction. It offers an opportunity to perform MI guided by action observation from 3PP with elicited SOO to the observed avatar. We believe that 3PP MI could provide more possibilities for effective rehabilitation training, when SOO could be elicited to a virtual avatar and the present work demonstrates its viability and effectiveness.

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Inclusive design does not stop at removing physical obstacles such as staircases. It also involves identifying architectural features that impose sensory burdens, such as repetitive visual patterns that are known to potentially cause dizziness or visual discomfort. In order to assess their influence on human gait and its stability, three repetitive patterns-random dots, repetitive stripes, and repetitive waves (Lisbon pattern)-were displayed in a coloured and greyscale variant in a virtual reality (VR) environment. The movements of eight participants were recorded using a motion capture system and electromyography (EMG). During all test conditions, a significant increase in the muscular activity of leg flexor muscles was identified just before touchdown. Further, an increase in the activity of laterally stabilising muscles during the swing phase was observed for all of the test conditions. The lateral and vertical centre of mass (CoM) deviation was statistically evaluated using a linear mixed model (LMM). The patterns did cause a significant increase in the CoM excursion in the vertical direction but not in the lateral direction. These findings are indicative of an inhibited and more cautious gait style and a change in control strategy. Furthermore, we quantified the induced discomfort by using both algorithmic estimates and self-reports. The Fourier-based methods favoured the greyscaled random dots over repetitive stripes. The colour metric favoured the striped pattern over the random dots. The participants reported that the wavey Lisbon pattern was the most disruptive. For architectural and structural design, this study indicates (1) that highly repetitive patterns should be used with care in consideration of their impact on the human visuomotor system and its behavioural effects and (2) that coloured patterns should be used with greater caution than greyscale patterns.

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The Delboeuf illusion occurs when two circles (test figures) of equal radius are placed side by side and surrounded by concentric circles (inducers) of varying radii, resulting in the test figure being misestimated depending on the size of the surrounding inducer. This study conducted three experiments to explore the impact of shape and the contour attraction and parallel attraction on the Delboeuf illusion for different shapes. In Experiment 1 (n = 64), the test figures remained as circles while the inducers varied in shape. Experiment 2 (n = 64) involved simultaneous changes in the shape of both the test figures and the inducers. Experiment 3 (n = 64) replicated Experiment 2, with the exception that the areas of the inducers were equal and the distances between the inducers and the test figures were also equal. We conclude that the shape of the inducer and the test figure had an impact on the visual size perception, and in the magnitude of the Delboeuf illusion, varied depending on contour attraction. Configurations with circles or shapes resembling circles exhibit contour attraction, while configurations with shapes possessing longer parallel lines shift toward parallel attraction, both attractions enhance the perceived magnitude of the Delboeuf illusion.

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We introduce a new illusory color phenomenon. The illusion is evoked by two alternating displays comprising various colored disks. Although the colors in the alternating displays are the same, the color appearance of the two displays are quite different. We suggest that apparent motion of the disks modulates the color percepts.

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Local vibration (LV) mainly stimulates primary afferents (Ia) and can induce a tonic vibration reflex (TVR) and an illusion of movement. This study aimed to evaluate the effect of these two phenomena on maximal voluntary isometric contraction (MVIC) capacity. LV (80 Hz) was applied to the wrist flexor muscles in two randomized experiments for 6 minutes. LV conditions were adjusted to promote either TVR (visual focus on the vibrated wrist) or ILLUSION (hand hidden, visual focus on electromyographic activity of the flexor carpi radialis muscle (FCR)). Mechanical and electromyographic (EMG) responses of the FCR and extensor carpi radialis muscles were recorded during MVIC in flexion and extension and during electrically evoked contractions at supramaximal intensity. Measurements were performed before (10 minutes and just before) and after (0 and 30 minutes) LV protocol. An increase in FCR EMG was observed during LV in the TVR condition (+340%) compared to the illusion condition (P=0.003). In contrast, the movement illusion was greater in the ILLUSION condition (assessed through subjective scales) (P=0.004). MVIC was reduced in flexion only after the TVR condition (≈ -7%, all P<0.034). Moreover, the decrease in force was correlated with the amount of TVR recorded on the FCR muscle (r=-0.64, P=0.005). Although potentiated doublets of each muscle did not evolve differently between conditions, a decrease was observed between the first and the last measure. In conclusion, when conducting research to assess maximal strength, it is necessary to have better control and reporting of the phenomena induced during LV.

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Previous research has demonstrated the existence of the face race lightness (FRL) illusion. It indicates that Black faces tend to appear darker than White faces, even when their luminance values are objectively adjusted to be the same. However, the debate over the exclusive influence of face-race categories on the FRL illusion continues, with the impact of racial groups on the illusion remaining relatively unexplored. To address these gaps, we conducted studies to investigate whether the FRL illusion varies in terms of racial salience and racial groups. We manipulated the racial salience by altering the orientation of the faces. A total of 64 Caucasians (Study 1) and 63 Asians (Study 2) were recruited. Participants were shown pairs of faces in rapid succession and were asked to report which face appeared lighter or darker. In each trial, the two faces belonged to the same race category: Black, Black-White ambiguous, or White. The luminance of the first face remained consistent across trials while the luminance of the second face varied and was adjusted across eight levels (- 20, - 12, - 8, - 4, + 4, + 8, + 12, + 20). Our findings reveal that the FRL illusion is largely dependent on the salience of face-race information. When faces were presented upright, the FRL illusion was prominent; however, it disappeared when faces were inverted. Remarkably, the FRL illusion was observed not only in Caucasians but also in Asians. Therefore, our results suggest that the FRL illusion primarily stems from race salience rather than participants' racial groups.

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BACKGROUND: Remote research methods and interventions for mental health disorders have become increasingly important, particularly for conditions like eating disorders (EDs). Embodiment illusions, which induce feelings of ownership over another person?s body or body parts, offer valuable insights into the mechanisms underlying self-perception issues in EDs and potential interventions. However, existing research using these illusions has been limited to face-to-face settings. We illustrate a novel online protocol to induce the enfacement illusion (embodiment illusion principles applied to one's face) in an ED-based sample. METHODS: Participants complete a 2-hr virtual session with a researcher. First, baseline trait/state ED psychopathology measures and a self-face recognition task occur. Second, participants experience two testing blocks of the enfacement illusion involving synchronously and asynchronously mimicking a pre-recorded actor's facial expressions. After each block, subjective and objective enfacement illusion measures occur alongside state ED psychopathology reassessment. DISCUSSION: Successfully inducing enfacement illusions online could provide an affordable, accessible virtual approach to further elucidate the mechanistic role of self-perception disturbances across psychopathologies such as EDs. Moreover, this protocol may represent an innovative, remotely-delivered intervention strategy, as 'enfacement' over another face could update negative self-representations in a cost-effective, scalable manner.