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Nihon Hoshasen Gijutsu Gakkai Zasshi Oct 2008Some cases have been reported in which an optical illusion of lightness perception influences the detectability in diagnosis of low-density hematoma in head CT images in...
Some cases have been reported in which an optical illusion of lightness perception influences the detectability in diagnosis of low-density hematoma in head CT images in addition to the visual impression of the photographic density of the brain. Therefore, in this study, the author attempted to compare the detectability in diagnosis for chest images with pneumothorax using visual subjective evaluation, and investigated the influence of optical illusion on that detectability in diagnosis. Results indicated that in the window setting of lung, on such an occasion when the low-absorption free space with pneumothorax forms a crescent or the reduced lung borders on the chest-wall, an optical illusion in which the visual impression on the difference of the film contrast between the lung and the low-absorption free space with pneumothorax was psychologically emphasized when contrast was observed. In all cases the detectability in diagnosis for original images with the white thorax and mediastinum was superior to virtual images. Further, in case of the virtual double window setting of lung, thorax, and mediastinum, under the influence of the difference in the radiological anatomy of thorax and mediastinum as a result of the grouping theories of lightness computation, an optical illusion different from the original images was observed.
Topics: Humans; Models, Anatomic; Optical Illusions; Pneumothorax; Tomography, X-Ray Computed
PubMed: 18987412
DOI: 10.6009/jjrt.64.1206 -
Journal of Experimental Psychology.... Apr 2014Visual illusions can reveal unconscious representations and processes at work in perception. Here we report a robust illusion that involves the misperception of moving,...
Visual illusions can reveal unconscious representations and processes at work in perception. Here we report a robust illusion that involves the misperception of moving, partially occluded objects. When a dynamically occluded object is seen through 2 misaligned apertures, the object appears misaligned in the direction of the apertures, creating the Aperture Capture Illusion. Specifically, when part of a dynamically occluded object disappears behind an occluding surface and then another part of the object comes into view immediately afterward, the 2 parts appear misaligned in the direction of the offset of the apertures through which they were seen. This illusion can be nulled: Separating the 2 object parts to increase the time interval between their appearance produced the percept of alignment. The ability to null the illusion in this manner demonstrates that dynamically occluded regions of moving objects continue to persist in perceptual awareness but, we argue, are perceived to move at a slower velocity than visible regions. We report 7 experiments establishing the existence of the illusion and ruling out several classes of explanation for it. We interpret the illusion and the ability to nullify it within the context of Palmer, Kellman, and Shipley's (2006) theory of spatiotemporal object formation.
Topics: Adult; Eye Movements; Form Perception; Humans; Motion Perception; Optical Illusions; Perceptual Masking; Pursuit, Smooth; Young Adult
PubMed: 24708425
DOI: 10.1037/a0035245 -
Psychological Research Mar 2016Many visual illusions result from assumptions of our visual system that are based on its long-term adaptation to our visual environment. Thus, visual illusions provide...
Many visual illusions result from assumptions of our visual system that are based on its long-term adaptation to our visual environment. Thus, visual illusions provide the opportunity to identify and learn about these fundamental assumptions. In this paper, we investigate the Ponzo illusion. Although many previous studies researched visual processing of the Ponzo illusion, only very few considered temporal processing aspects. However, it is well known that our visual percept is modulated by temporal factors. First, we used the Ponzo illusion as prime in a response priming task to test whether it modulates subsequent responses to the longer (or shorter) of two target bars. Second, we used the same stimuli in a perceptual task to test whether the Ponzo illusion is effective for very short presentation times (12 ms). We observed considerable priming effects that were of similar magnitude as those of a control condition. Moreover, the variations in the priming effects as a function of prime-target stimulus-onset asynchrony were very similar to that of the control condition. However, when analyzing priming effects as a function of participants' response speed, effects for the Ponzo illusion increased in slower responses. We conclude that although the illusion is established rapidly within the visual system, the full integration of context information is based on more time-consuming and later visual processing.
Topics: Adult; Female; Humans; Male; Optical Illusions; Photic Stimulation; Reaction Time; Visual Perception; Young Adult
PubMed: 25772166
DOI: 10.1007/s00426-015-0659-8 -
Vision Research Jan 2019A stimulus surrounded by smaller/larger stimuli appears larger/smaller (Ebbinghaus illusion). We examined whether the Ebbinghaus illusion would depend on the retinal or...
A stimulus surrounded by smaller/larger stimuli appears larger/smaller (Ebbinghaus illusion). We examined whether the Ebbinghaus illusion would depend on the retinal or perceived size of the surrounding stimuli. The flash-lag effect, where a flashed stimulus perceptually lags moving stimuli, was used to dissociate the retinal from perceived size of the surrounding stimuli. Two sets of four surrounding disks changed their size smoothly: one with larger disks shrinking, the other with smaller disks expanding. Two identical central disks were presented briefly at various timings relative to the moment when the surrounding disks were physically identical in their size (coincidence time). A significant flash-lag effect was observed for size change (Experiment 1). Participants reported the two central disks being in equal size when they appeared only slightly before the coincidence time. However, this asynchrony was not significantly different from zero and was significantly smaller than the perceptual delay expected from the flash-lag effect (Experiment 2). These results suggest that the Ebbinghaus illusion depends more on the retinal than perceived size of the surrounding stimuli.
Topics: Adolescent; Adult; Female; Humans; Male; Optical Illusions; Reaction Time; Retina; Size Perception; Young Adult
PubMed: 30389387
DOI: 10.1016/j.visres.2018.10.010 -
Experimental Brain Research Jun 2016It is generally accepted that visual illusions affect line bisection in the predicted direction. However, it has been reported an illusionary bias which seems...
It is generally accepted that visual illusions affect line bisection in the predicted direction. However, it has been reported an illusionary bias which seems questioning such general view. In a previous study, participants bisected lines flanked at both ends by two pairs of arrows, pointing in the same direction. The medialmost vertices of one pair converged on the line (converging arrows), whereas those of the other pair did not (non-converging arrows). Participants bisected lines toward the base of the arrows, i.e., toward the wider end of the stimulus and in the direction opposite to that predicted by the Baldwin illusion. However, the bisection bias was also directed away from the location of the converging arrows. We investigated what is the main factor affecting line bisection: arrows orientation, as previously suggested, or interference effects related to the location of converging arrows. In experiment 1, participants bisected lines flanked by converging versus non-converging arrows. Results confirmed the presence of a bisection bias directed not only toward the base of the converging arrows but also away from their location. In experiment 2, the arrows were located more internally, so that their medialmost vertices always converged on the line. Results showed that the bisection bias was directed away from the location of the arrows regardless of their orientation. It is suggested that the previously reported bisection bias did not depend on arrows orientation, but rather on interference effects related to converging arrows position. The theoretical implications of the results are discussed.
Topics: Adult; Attention; Female; Humans; Male; Optical Illusions; Space Perception; Visual Perception; Young Adult
PubMed: 26781491
DOI: 10.1007/s00221-015-4550-z -
Perception & Psychophysics Apr 1983
Topics: Afterimage; Form Perception; Humans; Illusions; Motion Perception; Optical Illusions
PubMed: 6866698
DOI: 10.3758/bf03205883 -
Perception Sep 2017While the two visual system hypothesis tells a fairly compelling story about perception and action in peripersonal space (i.e., within arm's reach), its validity for...
While the two visual system hypothesis tells a fairly compelling story about perception and action in peripersonal space (i.e., within arm's reach), its validity for extrapersonal space is very limited and highly controversial. Hence, the present purpose was to assess whether perception and action differences in peripersonal space hold in extrapersonal space and are modulated by the same factors. To this end, the effects of an optic illusion in perception and action in both peripersonal and extrapersonal space were compared in three groups that threw balls toward a target at a distance under different target eccentricity (i.e., with the target fixated and in peripheral field), viewing (i.e., binocular and monocular viewing), and delay conditions (i.e., immediate and delayed action). The illusory bias was smaller in action than in perception in peripersonal space, but this difference was significantly reduced in extrapersonal space, primarily because of a weakening bias in perception. No systematic modulation of target eccentricity, viewing, and delay arose. The findings suggest that the two visual system hypothesis is also valid for extra personal space.
Topics: Adult; Female; Humans; Male; Motor Activity; Optical Illusions; Personal Space; Space Perception; Vision, Binocular; Young Adult
PubMed: 28467169
DOI: 10.1177/0301006617707697 -
Perception Nov 2019
Topics: Depth Perception; Humans; Moon; Optical Illusions
PubMed: 31423942
DOI: 10.1177/0301006619868424 -
Vision Research Sep 2003The scintillating grid is a recently discovered visual illusion, created by superimposing white discs on the intersections of orthogonal gray bars on a black background....
The scintillating grid is a recently discovered visual illusion, created by superimposing white discs on the intersections of orthogonal gray bars on a black background. Even though the entire display is stationary, observers perceive dark spots appearing and disappearing rapidly within some of the white discs. This scintillation effect is correlated with eye position and eye movements. Here we investigate whether covert shifts of attention, as revealed by cueing and visual search paradigms, can also affect the illusion. We find that the chance of a particular intersection scintillating is directly correlated with distance from the attentional focus, regardless of the location of the fixation point. This suggests that the dynamics of this illusion might reflect the distribution of attention in space and time.
Topics: Analysis of Variance; Attention; Eye Movements; Female; Humans; Male; Optical Illusions; Pattern Recognition, Visual; Photic Stimulation; Visual Acuity
PubMed: 12885373
DOI: 10.1016/s0042-6989(03)00412-7 -
PsyCh Journal Jun 2018While observing a specific traffic sign in the field, we noticed an apparent distortion of size and shape of the circle that contained the sign. This novel illusion...
While observing a specific traffic sign in the field, we noticed an apparent distortion of size and shape of the circle that contained the sign. This novel illusion manifests as a distortion of the horizontal compared to the vertical dimension of the sign. The illusion seems to be underlined by similar mechanisms to those in the Delboeuf illusion. The aim of our study was to determine the existence and magnitude of the snow tire illusion. We conducted two experiments using the method of constant stimuli. The first experiment was conducted on the standard sign, while in the second, the stimuli were rotated 90° counterclockwise. Both experiments consisted of three conditions: the snow tire, the ellipse, and the simple circle (control) conditions. The data showed a robust illusion effect for both the standard and rotated sign compared to the control condition, with a large majority of participants experiencing the illusion. The snow tire illusion seems to be a combination of assimilation mechanisms of different magnitudes. The assimilation is larger for one dimension of the sign, thus producing the shape distortion. The illusion may be a manifestation of a thus far undocumented non-uniform effect of assimilation on perceived size and shape.
Topics: Adult; Female; Humans; Male; Optical Illusions; Pattern Recognition, Visual; Space Perception; Young Adult
PubMed: 29431259
DOI: 10.1002/pchj.208