Reduced influence of perceptual context in mild traumatic brain injury is not an illusion.

Perceptual grouping is impaired following mild traumatic brain injury (mTBI). This may affect visual size perception, a process influenced by perceptual grouping abilities. We conducted two experiments to evaluate visual size perception in people with self-reported history of mTBI, using two different size-contrast illusions: the Ebbinghaus Illusion (Experiment 1) and the Müller-Lyer illusion (Experiment 2). In Experiment 1, individuals with mTBI and healthy controls were asked to compare the size of two target circles that were either the same size or different sizes. The target circles appeared by themselves (no-context condition), or were surrounded by smaller or larger circles (context condition). Similar levels of accuracy were evident between the groups in the no-context condition. However, size judgements by mTBI participants were more accurate in the context condition, suggesting that they processed the target circles separately from the surrounding circles. In Experiment 2, individuals with mTBI and healthy controls judged the length of parallel lines that appeared with arrowheads (context condition) or without arrowheads (no context condition). Consistent with Experiment 1, size judgements by mTBI participants were more accurate than size judgements by control participants in the context condition. These findings suggest that mTBI influences size perception by impairing perceptual grouping of visual stimuli in near proximity.

Overlapping yet dissociable contributions of superiority illusion features to Ponzo illusion strength and metacognitive performance.

Humans are typically inept at evaluating their abilities and predispositions. People dismiss such a lack of metacognitive insight into their capacities while even enhancing (albeit illusorily) self-evaluation such that they should have more desirable traits than an average peer. This superiority illusion helps maintain a healthy mental state. However, the scope and range of its influence on broader human behavior, especially perceptual tasks, remain elusive. As belief shapes the way people perceive and recognize, the illusory self-superiority belief potentially regulates our perceptual and metacognitive performance. In this study, we used hierarchical Bayesian estimation and machine learning of signal detection theoretic measures to understand how the superiority illusion influences visual perception and metacognition for the Ponzo illusion. Our results demonstrated that the superiority illusion correlated with the Ponzo illusion magnitude and metacognitive performance. Next, we combined principal component analysis and cross-validated regularized regression (relaxed elastic net) to identify which superiority components contributed to the correlations. We revealed that the "extraversion" superiority dimension tapped into the Ponzo illusion magnitude and metacognitive ability. In contrast, the "honesty-humility" and "neuroticism" dimensions only predicted Ponzo illusion magnitude and metacognitive ability, respectively. These results suggest common and distinct influences of superiority features on perceptual sensitivity and metacognition. Our findings contribute to the accumulating body of evidence indicating that the leverage of superiority illusion is far-reaching, even to visual perception.

On the origin of the Ponzo illusion: An attentional account.

The Ponzo illusion is a famous optical illusion that is not well understood so far. Here we suggest that its origin is closely linked to distribution of spatial attention. In essence, it arises because the size of the attentional field varies between different parts of the stimulus layout, which comes with different spatial resolution and, as a consequence, different apparent sizes of the objects in the stimulus display. We report four experiments (conducted in 2022 and 2023), which support this approach. The illusion substantially decreases when the stimulus layout is modified so that the size of the supposed attentional field is equalized for the crucial parts (Experiment 1). Moreover, we induce a Ponzo-like illusion by means of attentional cues only (Experiment 2). The perceived spatial frequency differs for different parts of the stimulus layout consistent with predicted changes in spatial resolution (Experiment 3). Attentional cuing exerts an analogous influence on the apparent spatial frequency (Experiment 4). The presented approach provides a novel look at the origin of the Ponzo illusion and related phenomena. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Time and visual-spatial illusions: Evidence for cross-dimensional interference between duration and illusory size.

Time and space are intimately related to each other. Previous evidence has shown that stimulus size can affect perceived duration even when size differences are illusory. In the present study, we investigated the effect of visual-spatial illusions on duration judgments in a temporal reproduction paradigm. Specifically, we induced the Ebbinghaus illusion (Exp. 1) and the horizontal-vertical illusion (Exp. 2) during the encoding phase of the target interval or the reproduction phase. The results showed (a) that illusory size affects temporal processing similarly to the way physical size does, (b) that the effect is independent of whether the illusion appeared during encoding or reproduction, and (c) that the interference between size and temporal processing is bidirectional. These results suggest a rather late locus of size-time interference in the processing stream.

Exploring watercolor illusion spreading between dissected stimulus parts.

The watercolor illusion (WCI) occurs when an achromatic region is surrounded by an outer contour and inner chromatic fringe, resulting in an apparent pale tint of the same hue as the fringe. The WCI both fills in and spreads out, with the previous literature suggesting it always spreads out in the absence of an enclosing border. We examined how global stimulus configuration affects this illusion by dissecting various WCI-inducing stimuli into parts. Specifically, would color spread out of the unenclosed ends of the disconnected parts? Participants provided WCI illusion magnitude ratings and shading data indicating perceived locations of color spreading for a variety of stimulus configurations. Instead of the WCI spreading modally into the spaces between the disconnected parts, we found a global reorganization of the stimuli occurred. The dissected WCI stimuli were perceived as either amodally completed behind a white illusory surface perceptually different than the physically identical background or, as empty space between separate objects depending in part on the distance between dissected parts. This study demonstrates the WCI does not always spread outside of unenclosed borders when the global interpretation interferes with spreading. These findings highlight the importance of global configuration and perceptual organization in the WCI.

Optical illusions: The vital importance of instructions for use and intentionally approaching eye device processing.

BACKGROUND: The purpose of this process and quality improvement activity was to address opportunities identified with cleaning, disinfection, and sterilization requirements for eye devices, and implement a robust and sustainable processing system to support safe patient care. METHODS: Through the lean 6 Sigma methodology, the evaluation of noncritical, semicritical and critical device processing was conducted. A hierarchal approach to law, regulation, manufacturer's instructions for use, evidence-based guidelines, consensus documents, facility risk assessments, policy, and procedure was conducted. Over 15 diverse clinical areas within a large health care network were assessed for utilization of ophthalmic and optometric devices, with the review of inventory for manufacturer-instructed cleaning, disinfection and sterilization compliance. RESULTS: An interdepartmental multidisciplinary team with oversight of over 10 service lines led the implementation of point-of-use treatment, transport, high-level disinfection, sterilization, storage, and documentation based on intended use. CONCLUSIONS: During this experience, infection Preventionists performed a vital role in supporting a highly reliable cleaning, disinfection, and sterilization process. This undertaking required a team approach to apply instructions for uses and evidence-based practice that promoted sustainability and ultimately led to supporting the prevention of health care-associated infections and patient harm.

Müller-Lyer Illusion susceptibility is conditionally predicted by autistic trait expression.

Müller-Lyer (ML) figures bias size estimation consistently, yet different methods can lead to different degrees of illusory bias. Autistic individuals may also be less likely to perceive illusory biases with varying levels of autistic trait expression proposed to modulate reported illusory biases. The Autism-Spectrum Quotient (AQ) and Systemizing Quotient (SQ) are self-report measures that quantify autistic trait expression and systemizing ability in neurotypical individuals. The current study sought to determine if perceptions of illusory size bias negatively correlate with autistic trait expression and the extent to which varying methods of illusion presentation change the magnitude of illusory bias. Thirty neurotypical adults completed both questionnaires as well as four size estimation tasks. Two tasks involved perceptual discrimination of ML figures by concurrent and successive presentation, where participants selected the longer figure by keypress. For Tasks 3 and 4, participants adjusted the size of a non-illusory line (Task 3) or complementary illusory figure (Task 4) to match the perceived length. Overall, task performance was not correlated with autistic trait expression. One exception was a negative correlation with AQ when adjusting a complementary illusory ML figure in Task 4. Illusory biases were also stronger when two illusory figures were presented concurrently. Given these results, illusion susceptibility to the ML is suggested to be reduced with increases in AQ, but only when the method of illusion measurement is adjustment of concurrent illusory figures. Taken together the results provide evidence that traits associated with autism in a neurotypical population may systematically modulate perception.

Postcards related to Dentistry: Iron-Jaw Acts and aPromotional Optical Illusion.

Demonstrable feats of strength and valor using the teeth are found throughout many aspects of newsworthy items and social encounters in history past. Likewise, promotional opportunities relative to the dentition were also common. This article addresses many of these sensationalistic scenarios that were found on postcards related to dentistry in the early 1900s.

The Beep-Speed Illusion Cannot Be Explained With a Simple Selection Bias.

An object appears to move at higher speed than another equally fast object when brief nonspatial tones coincide with its changes in motion direction. We refer to this phenomenon as the beep-speed illusion (Meyerhoff et al., 2022, Cognition, 219, 104978). The origin of this illusion is unclear; however, attentional explanations and potential biases in the response behavior appear to be plausible candidates. In this report, we test a simple bias explanation that emerges from the way the dependent variable is assessed. As the participants have to indicate the faster of the two objects, participants possibly always indicate the audio-visually synchronized object in situations of perceptual uncertainty. Such a response behavior potentially could explain the observed shift in perceived speed. We therefore probed the magnitude of the beep-speed illusion when the participants indicated either the object that appeared to move faster or the object that appeared to move slower. If a simple selection bias would explain the beep-speed illusion, the response pattern should be inverted with the instruction to indicate the slower object. However, contrary to this bias hypothesis, illusion emerged indistinguishably under both instructions. Therefore, simple selection biases cannot explain the beep-speed illusion.

The box-circle illusion.

A novel geometrical optical illusion is reported in this article: the horizontal distances of the contextual structures distort the perceived vertical positions of observed objects. Specifically, the illusion manifests in the form of connected boxes of varying widths but equal heights, each containing a circle at the center. Despite identical vertical positioning of the circles, they appear misaligned. The illusion diminishes when the boxes are removed. Potential underlying mechanisms are discussed.

Effectiveness of the ability to form mental images in Müller-Lyer optical illusions.

The purpose of this study was to establish whether wing length and the ability to form spatial mental images and vivid images affected optical illusions obtained in the Müller-Lyer figures, both real and imagined. The study involved a group of 137 fine arts college students who were shown two forms of the Müller-Lyer figures with different wing length (15 and 45 mm). In the imagined situation, a plain horizontal line was presented, and participants were expected to imagine the arrowheads aligned in the same way as in the real situation. Discrepancies in the perception of the horizontal lines in the Müller-Lyer illusion ("Point of Subjective Equality") were measured both in the real and imagined situation. Participants were then asked to complete the Vividness of Visual Imagery Questionnaire and the Measure of the Ability to Form Spatial Mental Imagery. It emerged that, in the condition of 45 mm wing length, participants were significantly more susceptible to the illusion than those in the condition of 15 mm wing length. Additionally, in the real situation, participants scoring high in spatial image were significantly more resistant to the illusion than those scoring low.

Effects of normalized summation in the visual illusion of extent.

In the present study, the features of summation of effects caused by contextual distracting dots in the length-matching task (a variant of the filled-space illusion) were investigated. In the first two series of psychophysical experiments, the illusion magnitude was measured as a function of the displacement of distractors (either single or double sets of dots) orthogonally to the main axis of the stimulus. It was demonstrated that with increasing displacement, the illusion smoothly decreases for a single set of distractors, while for two sets, the illusion first increases to a certain maximum value, and then gradually decreases. In the third and fourth series of experiments, magnitude of the illusion was measured as a function of the luminance of one set of distracting dots, while the luminance of the other set was fixed. It has been shown that increasing the luminance until the same value is reached for both sets leads to a monotonous growth in the illusion magnitude; after that, the illusion asymptotically decreases to an almost constant level. The theoretical interpretation of the established functional dependencies was performed using a quantitative model based on the assumption that the illusion may arise due to the weighted summation of the distractor-induced normalized neural activity, which leads to the perceptual mislocalization of terminators of stimulus spatial intervals.

Effects of cortical distance on the Ebbinghaus and Delboeuf illusions.

The Ebbinghaus and Delboeuf illusions affect the perceived size of a target circle depending on the size and proximity of circular inducers or a ring. Converging evidence suggests that these illusions are driven by interactions between contours mediated by their cortical distance in primary visual cortex. We tested the effect of cortical distance on these illusions using two methods: First, we manipulated retinal distance between target and inducers in a two-interval forced choice design, finding that targets appeared larger with a closer surround. Next, we predicted that targets presented peripherally should appear larger due to cortical magnification. Hence, we tested the illusion strength when positioning the stimuli at various eccentricities, with results supporting this hypothesis. We calculated estimated cortical distances between illusion elements in each experiment and used these estimates to compare the relationship between cortical distance and illusion strength across our experiments. In a final experiment, we modified the Delboeuf illusion to test whether the influence of the inducers/annuli in this illusion is influenced by an inhibitory surround. We found evidence that an additional outer ring makes targets appear smaller compared to a single-ring condition, suggesting that near and distal contours have antagonistic effects on perceived target size.

Mario Ponzo (1928) on perception of numerosity: A translation and commentary.

Ponzo is a familiar name in psychology because of the illusion that takes his name. He had a long and productive career in Italy, and some of his work was translated for international journals already in his lifetime. However, few of these papers are available in English. We provide a commentary that considers how his name came to be associated with an illusion he did not discover. We explain the content of several papers, some of which are often cited in a wrong context in the literature (i.e., papers on touch mentioned in relation to the Ponzo illusion). More importantly, we discuss his contribution to the study of perceived numerosity, and provide a full translation of his important 1928 paper, including a redrawing of its 28 illustrations.

A novel visual illusion paradigm provides evidence for a general factor of illusion sensitivity and personality correlates.

Visual illusions are a gateway to understand how we construct our experience of reality. Unfortunately, important questions remain open, such as the hypothesis of a common factor underlying the sensitivity to different types of illusions, as well as of personality correlates of illusion sensitivity. In this study, we used a novel parametric framework for visual illusions to generate 10 different classic illusions (Delboeuf, Ebbinghaus, Rod and Frame, Vertical-Horizontal, Zöllner, White, Müller-Lyer, Ponzo, Poggendorff, Contrast) varying in strength, embedded in a perceptual discrimination task. We tested the objective effect of the illusions on errors and response times, and extracted participant-level performance scores (n=250) for each illusion. Our results provide evidence in favour of a general factor underlying the sensitivity to different illusions (labelled Factor i). Moreover, we report a positive link between illusion sensitivity and personality traits such as Agreeableness, Honesty-Humility, and negative relationships with Psychoticism, Antagonism, Disinhibition, and Negative Affect.

The role of line-orientation processing in the production of the Poggendorff illusion: A dual-task study.

Using a dual-task paradigm, the present investigation examined whether processes related to line orientation play a critical role in the production of the Poggendorff illusion. In Experiment 1, we assessed the magnitude of the Poggendorff illusion under three different task conditions. In the single-task condition, participants were asked to report how they perceive the alignment of transversal lines in the Poggendorff figure. In two different dual-task conditions, the participants were asked to read aloud the time displayed on a digital or analogue clock while also performing the Poggendorff perception task. The method of constant stimuli was used to calculate the point of subjective equality (PSE) and bistability width values, which represent illusion strength and perceptual uncertainty, respectively. PSEs indicated that the magnitude of the illusion did not vary between single, dual-analogue, and dual-digital task conditions, which suggests that the additional demands placed by the dual tasks had no effect on the illusion strength. Perceptual uncertainty and clock-reading errors were greater in the dual-analogue task condition. Experiment 2 revealed that the analogue clockface was more difficult to read than the digital clockface. Based on these results, we conclude that having participants perform a secondary task does not influence the magnitude of the Poggendorff illusion.

Sanford's L dissected: A partial replication and extension of Cai et al. (2017).

Partial replications of experiments reported by Cai et al. (Attention, Perception, & Psychophysics, 79(4), 1217-1226, 2017) on the so-called Horizontal-vertical illusion confirmed that dissecting L-figures into two separate lines yields greater overestimation of (near-)verticals than do intact Ls. However, contrary to Cai et al.'s findings, which had been obtained with a staircase procedure, with the method of constant stimuli, the amount of illusion was much smaller. This divergence is explained by the self-reinforcing nature of adjustment procedures. Another finding, already reported by Cormack and Cormack (Perception & Psychophysics, 16(2), 208-212, 1974), that obtuse angles between an L's lines yield greater bias than acute angles, was also replicated in one experiment but tended to be reversed in another. Mixing dissected, upright and top-down inverted Ls and laterally oriented Ts, both with tilted lines, within one experiment confirmed that the bias for Ts is opposite to the one for Ls: For Ts, the effect of (virtual) bisection dominates, yielding an overestimation of the length of the undivided line, whereas for Ls, the horizontal-vertical anisotropy dominates, yielding an overestimation of the length of the vertical line. The differential gap effects can possibly be explained by interactions within the neural substrate between orientation-sensitive and end-inhibited neurons, and the method effects by perceptual learning.

The Pulfrich solidity illusion: a surprising demonstration of the visual system's tolerance of solidity violations.

Physical objects behave following the principle of solidity: One solid object cannot pass through another. To what extent does the visual system integrate this physical regularity as a prior constraint? A new variant of the Pulfrich effect demonstrates a surprising degree of tolerance for violations of solidity when pitted against motion and depth cues. When adult participants view a pendulum swinging in the fronto-parallel plane with both eyes (one of which was covered by a light-attenuating filter), they falsely perceive the pendulum as swinging in an elliptical path (known as the "Pulfrich effect"). Here, we show that even when the pendulum's motion takes place entirely behind a solid horizontal bar, observers nevertheless see the pendulum pass through the bar while moving in an ellipse. This illusion suggests that the Pulfrich effect and the underlying stereoscopic depth cues can be robust to object solidity.

The long and short of it? A novel geometric illusion.

Here we present what we believe to be a novel geometric illusion where identical lines are perceived as being of differing lengths. Participants were asked to report which of the two parallel rows of horizontal lines contained the longer individual lines (two lines on one row and 15 on the other). Using an adaptive staircase we adjusted the length of the lines on the row containing two to estimate the point of subjective equality (PSE). At the PSE, the two lines were consistently shorter than the row containing the fixed length of 15 lines demonstrating a disparity in perceived length such that lines of identical length are perceived as longer in a row of two than in a row of 15. The illusion magnitude was unaffected by which row was presented above the other. Additionally, the effect persisted when using one as opposed to two test lines, and when the line stimuli on both rows were presented with alternating luminance polarity the illusion magnitude decreased, but was not abolished. The data indicate a robust geometric illusion that may be modulated by perceptual grouping processes.

Visual search of illusory contours: The role of illusory contour clarity.

Kanizsa-type illusory contours demonstrate an important function of the visual system-object inference from incomplete boundaries, which can be due to low luminance environments, camouflage, or occlusion. At a perceptual level, Kanizsa figures have been shown to have various degrees of clarity, depending on the features of the inducers. The aim of the present study is to evaluate whether contour clarity influences search efficiency of Kanizsa-type illusory contours. Experiment 1 will examine search for a Kanizsa-type illusory target among Kanizsa-type illusory distractors, by manipulating contour clarity using inducer size in three conditions, compared with search for a nonillusory perceptually grouped target among nonillusory perceptually grouped distractors with manipulated inducer size. Experiment 2 will address the effects of contour clarity on visual search by manipulating the number of arcs (i.e., line ends) comprising the inducers, in a visual search task of Kanizsa-type stimuli, compared with visual search for nonillusory grouped targets and distractors when the number of arcs are manipulated. To examine whether surface alterations had an impact on search in Experiment 1 due to changes in inducer size, Experiment 3 will examine search for Kanizsa stimuli formed from "smoothed" inducers, in comparison to search for Kanizsa stimuli used in Experiment 1. Together, these experiments will demonstrate whether contour clarity impacts visual search of illusory contours.