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Experimental Psychology Jul 2023An 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...
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, , , 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.
Topics: Humans; Illusions; Optical Illusions; Selection Bias; Motion Perception; Attention; Cognition
PubMed: 38105748
DOI: 10.1027/1618-3169/a000594 -
Heliyon Nov 2023According to research, it has been suggested that individuals who are affected by depression could potentially engage in the creation and experience emotional advantages...
UNLABELLED
According to research, it has been suggested that individuals who are affected by depression could potentially engage in the creation and experience emotional advantages relating to positive events directed towards the past or future, with the condition that they are provided with suitable mental imagery techniques. The main aim of this study was to assess the impact of utilizing positive imagery, specifically through the utilization of photographs featuring loved ones, on mood states and suicidal ideation among individuals diagnosed with depression and exhibiting suicidal tendencies. This randomized, double-blind, controlled crossover trial was conducted among 78 hospitalized depressive patients at three psychiatric services between April and August 2019. The patients participated in four individual picture-viewing sessions on four consecutive days. The four categories of pictures were included: loved ones, neutral faces of strangers, natural landscapes, and optical illusions. Directly prior to and immediately following the observation of the visual stimuli (photographs), the Brunel Mood Scale (BRUMS) and the Beck Scale for Suicide Ideation (BSSI) were completed by the patients. Repeated measures ANOVAs conducted in this study revealed a significant main effect of time on ratings of tension, depression, fatigue, vigor, calmness, and happiness (P values < 0.001). Additionally, statistically significant interactions were identified between picture category and time in relation to the variables of tension, depression, fatigue, vigor, calmness, and happiness (P values < 0.001). The analysis did not reveal a significant main effect of time on ratings of anger, confusion, and suicidal ideation (P values > 0.05). Likewise, the interaction between picture category and time did not yield significant results for the variables of anger, confusion, and suicidal ideation (P values > 0.05). The positive imagery procedure using the presentation of loved ones' photos showed beneficial effects on the mood states of depressed patients. The findings of this study suggest that incorporating a greater emphasis on positive imagery within the context of clinical depression may offer potential advantages. This highlights the potential for novel opportunities in the treatment of depression.
TRIAL REGISTRATION
The study has been registered in the Iranian Registry of Clinical Trials (registration number: IRCT20180808040744N1; first registration date: December 22, 2018; website: https://en.irct.ir/trial/33186).
PubMed: 38058624
DOI: 10.1016/j.heliyon.2023.e22312 -
IScience Dec 2023The neural and computational mechanisms underlying visual motion perception have been extensively investigated over several decades, but little attempt has been made to...
The neural and computational mechanisms underlying visual motion perception have been extensively investigated over several decades, but little attempt has been made to measure and analyze, how human observers perceive the map of motion vectors, or optical flow, in complex naturalistic scenes. Here, we developed a psychophysical method to assess human-perceived motion flows using local vector matching and a flash probe. The estimated perceived flow for naturalistic movies agreed with the physically correct flow (ground truth) at many points, but also showed consistent deviations from the ground truth (flow illusions) at other points. Comparisons with the predictions of various computational models, including cutting-edge computer vision algorithms and coordinate transformation models, indicated that some flow illusions are attributable to lower-level factors such as spatiotemporal pooling and signal loss, while others reflect higher-level computations, including vector decomposition. Our study demonstrates a promising data-driven psychophysical paradigm for an advanced understanding of visual motion perception.
PubMed: 38025782
DOI: 10.1016/j.isci.2023.108307 -
Optics Express Oct 2023Through engineering the emission features emanating from a light source, source illusions enable the generation of illusions in which observers viewing at a distance...
Through engineering the emission features emanating from a light source, source illusions enable the generation of illusions in which observers viewing at a distance misperceive the actual state of the source. However, those few efforts are significantly limited to the source transformation and metamaterials used. This limitation makes high-performance camouflaging of source emissions difficult to achieve. Even with basic functionalities such as source shifters camouflaging, source location remains difficult because the illusion is of low quality. Here, we demonstrate a way to improve substantially the camouflaging performance of a light-source shifter using topology optimization. Its scheme, objective function, and a few constraints are proposed. Generating an optimal topology for an all-dielectric light-source shifter is attempted for optical location camouflaging. Moreover, we succeed in designing very simple but high-performing source shifters despite several difficult properties such as multimodality. Our proposal extends the distance between the actual and virtual source locations that can be camouflaged and generates a broad band of frequencies for optical location camouflaging.
PubMed: 38017862
DOI: 10.1364/OE.503183 -
Current Biology : CB Dec 2023Contributions of the inner retinal photopigment melanopsin to human visual perception are incompletely understood. Here, we use a four-primary display to produce stimuli...
Contributions of the inner retinal photopigment melanopsin to human visual perception are incompletely understood. Here, we use a four-primary display to produce stimuli differing in melanopsin versus cone contrast in psychophysical paradigms in eight subjects with normal color vision. We address two predictions from electrophysiological recordings of the melanopsin system in non-human mammals: melanopsin influences color and/or supports image persistence under visual fixation. We first construct chromatic contrast sensitivity contours for stimuli differing in melanopsin excitation presented as a central annulus (10°) or peripheral (22.5°) spot. We find that although including melanopsin contrast produces modest changes in the average chromatic coordinates in both eccentricities, this occurs equally at low (0.5 Hz) and higher (3.75 Hz) temporal frequencies, arguing that it reflects divergence in cone spectral sensitivity in our participants from that captured in standardized cone fundamentals rather than a melanopsin contribution to color. We continue to ask whether the established ability of melanopsin to sustain firing of visual neurons under extended light exposure has a visual correlate, using the optical illusion of Troxler fading in which blurred spots in periphery disappear during visual fixation. We find that introducing additional melanopsin contrast (+28% Michelson contrast) to either bright or dark spots increases fading latency by 35% ± 8.8% and 41% ± 13.6%, respectively. Our data argue that the primary contribution of melanopsin to perception under these conditions is not to provide a color percept but rather to enhance persistence of low spatial frequency patterns during visual fixation.
Topics: Animals; Humans; Photic Stimulation; Retina; Retinal Cone Photoreceptor Cells; Vision, Ocular; Rod Opsins; Mammals
PubMed: 37967553
DOI: 10.1016/j.cub.2023.10.039 -
PloS One 2023Apparent motion is a visual illusion in which stationary stimuli, flashing in distinct spatial locations at certain time intervals, are perceived as one stimulus moving...
Apparent motion is a visual illusion in which stationary stimuli, flashing in distinct spatial locations at certain time intervals, are perceived as one stimulus moving between these locations. In the primary visual cortex, apparent-motion stimuli produce smooth spatio-temporal patterns of activity similar to those produced by continuously moving stimuli. An important prerequisite for producing such activity patterns is prolongation of responses to brief stimuli. Indeed, a brief stimulus can evoke in the visual cortex a long response, outlasting the stimulus by hundreds of milliseconds. Here we use firing-rate based models with simple ring structure, and biologically-detailed conductance-based refractory density (CBRD) model with retinotopic space representation to analyze the response retention and the origin of smooth profiles of activity in response to apparent-motion stimuli. We show that the strength of recurrent connectivity is the major factor that endorses neuronal networks with the ability for response retention. The same strengths of recurrent connections mediate the appearance of bump attractor in the ring models. Factors such as synaptic depression, NMDA receptor mediated currents, and conductances regulating spike adaptation influence response retention, but cannot substitute for the weakness of recurrent connections to reproduce response retention in models with weak connectivity. However, the weakness of lateral recurrent connections can be compensated by layering: in multi-layer models even with weaker connections the activity retains due to its feedforward propagation from layer to layer. Using CBRD model with retinotopic space representation we further show that smooth spatio-temporal profiles of activity in response to apparent-motion stimuli are produced in the models expressing response retention, but not in the models that fail to produce response retention. Together, these results demonstrate a link between response retention and the ability of neuronal networks to generate spatio-temporal patterns of activity, which are compatible with perception of apparent motion.
Topics: Motion Perception; Photic Stimulation; Neurons; Visual Cortex; Motion; Visual Perception
PubMed: 37917779
DOI: 10.1371/journal.pone.0293725 -
Perception Sep 2023A novel geometrical optical illusion is reported in this article: the horizontal distances of the contextual structures distort the perceived vertical positions of...
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.
Topics: Humans; Orientation; Optical Illusions
PubMed: 37427447
DOI: 10.1177/03010066231186557 -
Attention, Perception & Psychophysics Feb 2024Time and space are intimately related to each other. Previous evidence has shown that stimulus size can affect perceived duration even when size differences are...
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.
Topics: Humans; Illusions; Size Perception; Judgment; Time Perception; Optical Illusions; Visual Perception
PubMed: 37386344
DOI: 10.3758/s13414-023-02737-x -
BMC Ophthalmology Jun 2023Cataracts affect the optics of the eye in terms of absorption, blur, and scattering. When cataracts are unilateral, they cause differences between the eyes that can...
BACKGROUND
Cataracts affect the optics of the eye in terms of absorption, blur, and scattering. When cataracts are unilateral, they cause differences between the eyes that can produce visual discomfort and harm binocular vision. These interocular differences can also induce differences in the processing speed of the eyes that may cause a spontaneous Pulfrich effect, a visual illusion provoking important depth misperceptions. Interocular differences in light level, like those present in unilateral cataracts, can cause the Classic Pulfrich effect, and interocular differences in blur, like those present in monovision, a common correction for presbyopia, can cause the Reverse Pulfrich effect. The visual system may be able to adapt, or not, to the new optical condition, depending on the degree of the cataract and the magnitude of the monovision correction.
CASE PRESENTATION
Here, we report a unique case of a 45-year-old patient that underwent unilateral cataract surgery resulting in a monovision correction of 2.5 diopters (D): left eye emmetropic after the surgery compensated with a monofocal intraocular lens and right eye myopic with a spherical equivalent of -2.50 D. This patient suffered severe symptoms in binocular vision, which can be explained by a spontaneous Pulfrich effect (a delay measured of 4.82 ms, that could be eliminated with a 0.19 optical density filter). After removing the monovision with clear lens extraction in the second eye, symptoms disappeared. We demonstrate that, at least in this patient, both Classic and Reverse Pulfrich effects coexist after unilateral cataract surgery and that can be readapted by reverting the interocular differences. Besides, we report that the adaptation/readaptation process to the Reverse Pulfrich effect happens in a timeframe of weeks, as opposed to the Classic Pulfrich effect, known to have timeframes of days. Additionally, we used the illusion measured in the laboratory to quantify the relevance of the spontaneous Pulfrich effect in different visual scenarios and tasks, using geometrical models and optic flow algorithms.
CONCLUSIONS
Measuring the different versions of the Pulfrich effect might help to understand the visual discomfort reported by many patients after cataract surgery or with monovision and could guide compensation or intervention strategies.
Topics: Humans; Middle Aged; Vision, Monocular; Cataract Extraction; Lenses, Intraocular; Lens Implantation, Intraocular; Cataract; Presbyopia
PubMed: 37353733
DOI: 10.1186/s12886-023-03041-w -
Perception Jul 2023The 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...
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.
Topics: Humans; Illusions; Optical Illusions; Size Perception; Gravitation; Retina
PubMed: 37335155
DOI: 10.1177/03010066231175014