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Vision Research Dec 2020The eggs illusion is a visual phenomenon in which bright circular patches located at the midpoints between the intersections of a dark grid are perceived as being...
The eggs illusion is a visual phenomenon in which bright circular patches located at the midpoints between the intersections of a dark grid are perceived as being elongated along the direction orthogonal to the grid line. In the four experiments we report here, we explored the spatial properties of the eggs illusion by manipulating retinal eccentricity and the location of the stimulus in the visual field. In Experiment 1, we examined whether central and peripheral configurations affected the illusory magnitude. In Experiment 2, we varied the spatial location of grid patterns and found that the eggs illusion was intensified when the pattern was presented in the horizontal, not vertical or diagonal position, relative to the fixation. In Experiment 3, we varied the retinal eccentricity of the pattern along the horizontal meridian and found that the illusion was enhanced in the retinal periphery. In Experiment 4, we manipulated the size of the stimulus and found that peripheral enhancement of the eggs illusion was more apparent for a larger pattern. The visual field anisotropy and the peripheral enhancement of the eggs illusion are discussed in relation to mechanisms underlying grid-induced illusions.
Topics: Anisotropy; Humans; Optical Illusions; Pattern Recognition, Visual; Visual Fields; Visual Perception
PubMed: 32932126
DOI: 10.1016/j.visres.2020.08.008 -
Vision Research Jul 2018In the retinal image of the natural world, edges and shapes can be defined by first-order attributes, such as luminance, and second-order attributes, such as contrast...
In the retinal image of the natural world, edges and shapes can be defined by first-order attributes, such as luminance, and second-order attributes, such as contrast and texture. Previous studies have suggested that, in the human visual system, these attributes are initially detected separately and integrated later. Thus, comparing the strength of different geometrical optical illusions in stimuli, in which different elements are defined by the same or different attributes, is helpful to investigate at which stage the underlying mechanism of the illusion is located. We investigated whether there is a single common mechanism underlying the Ebbinghaus illusion in stimuli defined by different attributes. We used the traditional Ebbinghaus (Titchener) illusion figure: a target disk surrounded by smaller or larger inducer disks. The background and stimuli consisted of sine-wave gratings. We manipulated the luminance, contrast, and grating orientations of the target disk and inducer disks to create stimuli defined by each of these attributes. We then examined whether the illusion occurred in stimuli defined by each single attribute and in compound stimuli, in which the target and inducers were defined by different attributes. We found that the Ebbinghaus illusion occurred with the same strength in stimuli defined by all three attributes. We also found an asymmetry, such as the second-order inducers affected the first-order target less than they affected the second-order targets, but the first-order inducers affected all targets similarly. Our findings suggest that different attributes are likely to be integrated into a cue-invariant shape representation prone to the Ebbinghaus illusion. However, first-order and second-order stimuli may differently contribute to the quantitative aspect of the illusion, resulting in the asymmetric illusion strength.
Topics: Adult; Analysis of Variance; Contrast Sensitivity; Cues; Female; Humans; Male; Optical Illusions; Orientation, Spatial; Photic Stimulation; Visual Perception; Young Adult
PubMed: 29758217
DOI: 10.1016/j.visres.2018.04.006 -
Perception 2009
Topics: Art; Form Perception; Humans; Optical Illusions; Rotation; Science
PubMed: 20192124
DOI: 10.1068/p3812ed -
Neuron Nov 2020Direction-selective (DS) neurons compute the direction of motion in a visual scene. Brain-wide imaging in larval zebrafish has revealed hundreds of DS neurons scattered...
Direction-selective (DS) neurons compute the direction of motion in a visual scene. Brain-wide imaging in larval zebrafish has revealed hundreds of DS neurons scattered throughout the brain. However, the exact population that causally drives motion-dependent behaviors-e.g., compensatory eye and body movements-remains largely unknown. To identify the behaviorally relevant population of DS neurons, here we employ the motion aftereffect (MAE), which causes the well-known "waterfall illusion." Together with region-specific optogenetic manipulations and cellular-resolution functional imaging, we found that MAE-responsive neurons represent merely a fraction of the entire population of DS cells in larval zebrafish. They are spatially clustered in a nucleus in the ventral lateral pretectal area and are necessary and sufficient to steer the entire cycle of optokinetic eye movements. Thus, our illusion-based behavioral paradigm, combined with optical imaging and optogenetics, identified key circuit elements of global motion processing in the vertebrate brain.
Topics: Afterimage; Animals; Animals, Genetically Modified; Eye Movements; Motion Perception; Neuroimaging; Optical Illusions; Optogenetics; Photic Stimulation; Pretectal Region; Zebrafish
PubMed: 32966764
DOI: 10.1016/j.neuron.2020.08.027 -
BMC Neuroscience Mar 2011The perceived size of objects not only depends on their physical size but also on the surroundings in which they appear. For example, an object surrounded by small items...
BACKGROUND
The perceived size of objects not only depends on their physical size but also on the surroundings in which they appear. For example, an object surrounded by small items looks larger than a physically identical object surrounded by big items (Ebbinghaus illusion), and a physically identical but distant object looks larger than an object that appears closer in space (Ponzo illusion). Activity in human primary visual cortex (V1) reflects the perceived rather than the physical size of objects, indicating an involvement of V1 in illusory size perception. Here we investigate the role of eye-specific signals in two common size illusions in order to provide further information about the mechanisms underlying illusory size perception.
RESULTS
We devised stimuli so that an object and its spatial context associated with illusory size perception could be presented together to one eye or separately to two eyes. We found that the Ponzo illusion had an equivalent magnitude whether the objects and contexts were presented to the same or different eyes, indicating that it may be largely mediated by binocular neurons. In contrast, the Ebbinghaus illusion became much weaker when objects and their contexts were presented to different eyes, indicating important contributions to the illusion from monocular neurons early in the visual pathway.
CONCLUSIONS
Our findings show that two well-known size illusions - the Ponzo illusion and the Ebbinghaus illusion - are mediated by different neuronal populations, and suggest that the underlying neural mechanisms associated with illusory size perception differ and can be dependent on monocular channels in the early visual pathway.
Topics: Adult; Female; Functional Laterality; Humans; Male; Neuropsychological Tests; Optical Illusions; Photic Stimulation; Reaction Time; Size Perception; Space Perception; Statistics as Topic; Transfer, Psychology; Young Adult
PubMed: 21396093
DOI: 10.1186/1471-2202-12-27 -
Tijdschrift Voor Psychiatrie 2020The name Maurits Escher is inextricably linked with the notion of 'optical illusion', a type of illusion evoked by his 'impossible figures'. Despite the sober style in...
The name Maurits Escher is inextricably linked with the notion of 'optical illusion', a type of illusion evoked by his 'impossible figures'. Despite the sober style in which he realised these figures, they go on to mesmerise generations of art lovers. It is unclear what causes this, and whether other factors than aesthetic ones are involved.
AIM: To gain insight into the genesis of optical illusions in Escher's work, and in the role of the perceptual system in that process.
METHOD: An explorative literature search in PubMed, Science.gov, Google Scholar, and the historical literature.
RESULTS: Since 'impossible figures' cannot be found in our natural environment, and therefore have a high novelty factor to the brain, they inevitably draw our attention. The reason that we remain captivated, is at least partly associated with the fact that the hippocampus and parahippocampal place area come into conflict with each other, and (in vain) accept the challenge to find a 'best fit'.
CONCLUSION: Fundamental research may benefit from Escher's 'impossible figures' to fathom the rules of our visual grammar. The optical illusions they evoke moreover constitute an ongoing source of inspiration for other artists, architects, and film makers.Topics: Art; Humans; Illusions; Male; Optical Illusions
PubMed: 32484566
DOI: No ID Found -
Medicina (Kaunas, Lithuania) 2009The Oppel-Kundt illusion was examined in the psychophysical experiments with the classical two-part stimuli and modified three-part figures. The modified versions...
The Oppel-Kundt illusion was examined in the psychophysical experiments with the classical two-part stimuli and modified three-part figures. The modified versions comprised either one filled medial interval and two empty flanking intervals or one empty space situated in between two fillings. The illusion was measured as a function of the number of filling elements in the referential parts of the figures. The curves obtained by two modified figures and by the original two-part stimulus were quite similar in shape, but the magnitudes of the illusions differed significantly. The figure with two filled intervals yielded about twice-stronger illusory effect than the contrasting figure with a single filled and two empty intervals. The two-part stimulus showed the illusion magnitudes in the midst. Our assumption suggests the illusory effect being related particularly to over estimations of the filled interval when compared with the empty interval displayed side-to-side. The unfilled interval might not contribute to the illusion.
Topics: Humans; Optical Illusions; Photic Stimulation; Psychophysics; Size Perception
PubMed: 20051719
DOI: No ID Found -
Vision Research Apr 2011The past quarter century has witnessed considerable advances in our understanding of Lightness (perceived reflectance), Brightness (perceived luminance) and perceived... (Review)
Review
The past quarter century has witnessed considerable advances in our understanding of Lightness (perceived reflectance), Brightness (perceived luminance) and perceived Transparency (LBT). This review poses eight major conceptual questions that have engaged researchers during this period, and considers to what extent they have been answered. The questions concern 1. the relationship between lightness, brightness and perceived non-uniform illumination, 2. the brain site for lightness and brightness perception, 3 the effects of context on lightness and brightness, 4. the relationship between brightness and contrast for simple patch-background stimuli, 5. brightness "filling-in", 6. lightness anchoring, 7. the conditions for perceptual transparency, and 8. the perceptual representation of transparency. The discussion of progress on major conceptual questions inevitably requires an evaluation of which approaches to LBT are likely and which are unlikely to bear fruit in the long term, and which issues remain unresolved. It is concluded that the most promising developments in LBT are (a) models of brightness coding based on multi-scale filtering combined with contrast normalization, (b) the idea that the visual system decomposes the image into "layers" of reflectance, illumination and transparency, (c) that an understanding of image statistics is important to an understanding of lightness errors, (d) Whittle's logW metric for contrast-brightness, (e) the idea that "filling-in" is mediated by low spatial frequencies rather than neural spreading, and (f) that there exist multiple cues for identifying non-uniform illumination and transparency. Unresolved issues include how relative lightness values are anchored to produce absolute lightness values, and the perceptual representation of transparency. Bridging the gap between multi-scale filtering and layer decomposition approaches to LBT is a major task for future research.
Topics: Contrast Sensitivity; Humans; Lighting; Models, Biological; Optical Illusions; Photic Stimulation; Visual Perception
PubMed: 20858514
DOI: 10.1016/j.visres.2010.09.012 -
Scientific Reports Apr 2023Visual illusions are a gateway to understand how we construct our experience of reality. Unfortunately, important questions remain open, such as the hypothesis of a...
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.
Topics: Humans; Illusions; Optical Illusions; Size Perception; Personality Disorders; Personality
PubMed: 37087480
DOI: 10.1038/s41598-023-33148-5 -
Perception 2012We report three experiments intended to characterise aspects of the 'double face' illusion, formed by replicating the eyes and mouth below the originals. Such doubled...
We report three experiments intended to characterise aspects of the 'double face' illusion, formed by replicating the eyes and mouth below the originals. Such doubled faces are disturbing to look at. We find there are wide individual differences in the ability to detect that a face has been doubled when presented briefly and masked. These differences appear to relate to perceptual speed, since they correlate with the ability to identify a briefly presented famous face. Doubling has a significant effect on identification, though much less than inversion. In a reaction-time study, participants are faster to decide that a face has been doubled as it is rotated away from upright. The final study shows that normal and doubled faces do not pop out from each other, but reveals a processing overhead of 40-60 ms per doubled face. We offer some speculations as to the cause of the perceptual effects.
Topics: Adult; Face; Female; Humans; Male; Optical Illusions; Pattern Recognition, Visual; Photic Stimulation; Reaction Time; Visual Perception
PubMed: 22611664
DOI: 10.1068/p6720