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1.
Perception ; 50(2): 170-173, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33459169

RESUMO

If somebody gazes at your left eye, you perceive them as looking straight at you. They switch their gaze with a single saccade to your right eye. You see their eyes move, yet they paradoxically end up still looking straight at you. Comparable paradoxical effects can arise when you view your own selfie image on a phone screen-but not when you look in a mirror.

2.
Iperception ; 11(3): 2041669520937029, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32874528

RESUMO

Peripherally viewed targets moved around against a background of random dynamic noise. Slow movements were visible, fast movements were not. Thus, a target that repetitively drifted to the right and snapped back appeared to drift endlessly to the right with no visible snapbacks.

3.
Iperception ; 11(3): 2041669520929047, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32547725

RESUMO

A test cross that flickers between light yellow and dark blue at 5 to 8Hz looks apparently yellow on a dark gray surround and apparently blue on a light gray surround (flicker augmented contrast). The achromatic surround cannot be inducing the perceived colors. Instead, the visual system selects the more salient apparent color with the higher Michelson contrast. The same is true for dichoptic vision. When one eye views a steady, light yellow cross and the other eye views a congruent steady dark blue cross, the binocular combination of colors looks apparently yellow on a dark gray surround and apparently blue on a light gray surround. Thus, when competing stimuli are distributed over time (flicker) or space (dichoptic vision), the visual system overweights the stimulus with the higher contrast. To see objects clearly, we accept the best view of any object and downplay inferior alternatives.

5.
Iperception ; 10(5): 2041669519879178, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31656579

RESUMO

The flash-grab effect made a stationary flashing cross appear to jump back and forth through a distance of more than 2°. Observers were asked to move a cursor as quickly as possible on to this flashing target. All observers younger than 65 years, and 39% of those over 65 years, could do this without difficulty within 1 second to 2 seconds. But 61% of those over 65 years experienced uncertainty about the exact position of the target and took from 6 to 147 seconds to hit it-about 4 times longer than to hit an actually jumping cross. This loss of hand-eye coordination was probably perceptual, not motor.

6.
Iperception ; 10(4): 2041669519856906, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31384414

RESUMO

Reversed apparent motion (or reversed phi) can be seen during a continuous dissolve between a positive and a spatially shifted negative version of the same image. Similar reversed effects can be seen in stereo when positive and spatially shifted negative images are presented separately to the two eyes or in a Vernier alignment task when the two images are juxtaposed one above the other. Gregory and Heard reported similar effects that they called "phenomenal phenomena." Here, we investigate the similarities between these different effects and put forward a simple, spatial-smoothing explanation that can account for both the direction and magnitude of the reversed effects in the motion, stereo and Vernier domains. In addition, we consider whether the striking motion effects seen when viewing Kitaoka's colour-dependent Fraser-Wilcox figures are related to the reversed phi illusion, given the similarity of the luminance profiles.

9.
Iperception ; 9(4): 2041669518765852, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30275943

RESUMO

In specially constructed movies depicting moving eyes, the pupils, irises, and corneal reflexes moved independently and sometimes in opposite directions. We found that the moving pupils or the corneal reflex, not the moving irises, determined the perceived direction of gaze (online Movie 1). When the pupils and irises moved in opposite directions, the one with the higher Michelson contrast determined the perceived direction of gaze (online Movie 2).

10.
Iperception ; 9(5): 2041669518801029, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30302188

RESUMO

A spot moves vertically across a large grating of oblique parallel lines. When viewed peripherally, the motion path looks oblique, close to the orientation of the background grating. Even when the grating's orientation is concealed by crowding, it can still deflect the spot's perceived motion path.

11.
Iperception ; 9(4): 2041669518791833, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30123487

RESUMO

Ambiguous bounce/stream collision points were hidden behind an occluder so that observers had to complete them amodally. In Movie 1, straight or curved static lines were painted on the occluder. In Movie 2, dotted textures flowed in straight or curved lines across the front of the occluder. In Movie 3, moving eyes, painted on the occluder, either moved in straight lines, as if tracking streaming spots, or else followed curved paths, as if tracking bouncing spots. The straight (or curved) lines, texture flow or eye movements led to judgments of streaming (or bouncing). These effects demonstrate the role of attention and expectations in disambiguating bounce/stream stimuli.

12.
Iperception ; 9(4): 2041669518770690, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30083307

RESUMO

A Cornsweet edge creates the perception of a step in surface lightness between two adjacent regions of identical mean luminance due to a gradient on both sides. We might imagine that in a concatenated set of these gradients, the lightness steps would accumulate, but they do not. However, a diamond pattern, with each diamond filled with an identical luminance gradient does give a cumulative Cornsweet effect. Here, we offer an illumination explanation for why the cumulative effect is visible in the diamonds but not in the basic ramp grating and we demonstrate that when the diamonds drift, they produce a strong brightening effect (depending on the direction of the motion) and a dimming aftereffect. These effects are consistent with the local luminance gradients and not with the global lightness shift of the cumulative Cornsweet effect.

13.
Vision Res ; 146-147: 32-40, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29499211

RESUMO

Reducing the amount of motion information can surprisingly make motion look faster (e.g., motion behind Venetian blinds). We found that a textured pattern moving to the right at speeds ranging from 0.34 to 5.5°/s appeared to move 50% faster when viewed through a short (0.5°) compared with a long (4.5°) horizontal slot. Perceived speed varied inversely with the log of the slot length. We varied the length of rectangular apertures over a tenfold range and manipulated their size, shape, and orientation. We attribute the field-size effect mostly to landmarks provided by the ends of the slots, but we also examined temporal and spatial frequency and lateral inhibition of motion.


Assuntos
Percepção de Movimento/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Campos Visuais/fisiologia , Humanos , Ilusões Ópticas , Orientação Espacial , Tempo de Reação
14.
Iperception ; 9(6): 2041669518811305, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30627412

RESUMO

Lines in the café wall illusion, and motion trajectories in the furrow illusion, appear to be tilted away from their true orientations. We adapted to moving versions of both illusions and found that the resulting motion aftereffects were appropriate to their perceptual, not their physical, orientations.

15.
Iperception ; 8(6): 2041669517737561, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29201338

RESUMO

A random-dot background was expanded and contracted, and rotated, or expanded in one dimension while contracting on the other, or skewed back and forth horizontally. Squares that were flashed at the reversal points of these affine pattern distortions, aligned to edges in the texture, showed massive changes in size and shape.

16.
Iperception ; 8(3): 2041669517707972, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28560014

RESUMO

The perceived speed of a ring of equally spaced dots moving around a circular path appears faster as the number of dots increases (Ho & Anstis, 2013, Best Illusion of the Year contest). We measured this "spinner" effect with radial sinusoidal gratings, using a 2AFC procedure where participants selected the faster one between two briefly presented gratings of different spatial frequencies (SFs) rotating at various angular speeds. Compared with the reference stimulus with 4 c/rev (0.64 c/rad), participants consistently overestimated the angular speed for test stimuli of higher radial SFs but underestimated that for a test stimulus of lower radial SFs. The spinner effect increased in magnitude but saturated rapidly as the test radial SF increased. Similar effects were observed with translating linear sinusoidal gratings of different SFs. Our results support the idea that human speed perception is biased by temporal frequency, which physically goes up as SF increases when the speed is held constant. Hence, the more dots or lines, the greater the perceived speed when they are moving coherently in a defined area.

17.
Iperception ; 8(3): 2041669517707766, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28567269

RESUMO

In simultaneous contrast of spatial frequency (SF), a test grating surrounded by a coarser inducing grating looks apparently finer. We combined this effect with another visual illusion; the fact that flickering the inducing grating raises its apparent SF. We found that the inducer's apparent, not physical spatial frequency, drove the simultaneous contrast that it induced into a test grating. Thus, when the inducer was made to flicker, its SF appeared to be higher and consequently, the test's SF appeared lower than before. This suggests that simultaneous contrast of spatial frequency exists further downstream than the flicker-induced increase in perceived SF.

18.
Iperception ; 8(2): 2041669517699414, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28529686

RESUMO

A patch that alternates between two hues such as dark green and light blue looks greenish on a light gray surround and bluish on a dark gray surround ("flicker-augmented contrast"). Thus, when an edge alternates between two hues in the same location, the visual system selects the more salient hue-the one with the higher Michelson contrast. However, the afterimage is the same pink, driven by the time integral of the physical, not the perceptual, adapting hues and regardless of the surround luminance. So the process of edge biasing does not transfer to the mechanism that creates afterimages.

19.
J Vis ; 17(4): 7, 2017 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-28423412

RESUMO

Kaneko and Murakami (2012) demonstrated that simultaneous contrast for brightness and color (chromatic saturation) were enhanced by flashing the stimulus very briefly (10 ms). Here we examined whether this effect of duration generalized to other visual features. Tilt illusion and simultaneous hue contrast were both shown to be much stronger with a stimulus duration of 10 ms compared with 500 ms. The similar temporal dynamics for simultaneous contrast across visual features suggest common underlying principles.


Assuntos
Percepção de Cores/fisiologia , Sensibilidades de Contraste/fisiologia , Ilusões/fisiologia , Análise de Variância , Cor , Humanos , Orientação , Estimulação Luminosa/métodos , Fatores de Tempo
20.
Iperception ; 7(5): 2041669516664741, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27698989

RESUMO

Rotating squares appeared to be distorted into pincushions with concave sides. These illusory shape changes were caused by a perceived compression along the curved path of motion.

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