Contrast Configuration Influences Grouping in Apparent Motion

Perception ◽  
10.1068/p3444 ◽  
2005 ◽  
Vol 34 (6) ◽  
pp. 669-685 ◽  
Author(s):  
Anna Ma-Wyatt ◽  
Colin W G Clifford ◽  
Peter Wenderoth
Keyword(s):  
Apparent Motion ◽  
Contrast Polarity ◽  
Ternus Display ◽  
Static Display ◽  
Stereo Display ◽  
Motion Responses ◽  
Group Motion ◽  
Similar Dependence ◽  
Opposite Contrast

We investigated whether the same principles that influence grouping in static displays also influence grouping in apparent motion. Using the Ternus display, we found that the proportion of group motion reports was influenced by changes in contrast configuration. Subjects made judgments of completion of these same configurations in a static display. Generally, contrast configurations that induced a high proportion of group motion responses were judged as more ‘complete’ in static displays. Using a stereo display, we then tested whether stereo information and T-junction information were critical for this increase in group motion. Perceived grouping was consistently higher for same contrast polarity configurations than for opposite contrast polarity configurations, regardless of the presence of stereo information or explicit T-junctions. Thus, while grouping in static and moving displays showed a similar dependence on contrast configuration, motion grouping showed little dependence on stereo or T-junction information.

Multimodal Ternus: Visual, Tactile, and Visuo — Tactile Grouping in Apparent Motion

Perception ◽  
10.1068/p5844 ◽  
2007 ◽  
Vol 36 (10) ◽  
pp. 1455-1464 ◽  
Author(s):  
Vanessa Harrar ◽  
Laurence R Harris
Keyword(s):  
Stimulus Onset Asynchrony ◽  
Apparent Motion ◽  
Visual Stimuli ◽  
Stimulus Onset ◽  
Light Touch ◽  
Visual Group ◽  
Motion Stimulus ◽  
Group Motion ◽  
Onset Asynchrony

Gestalt rules that describe how visual stimuli are grouped also apply to sounds, but it is unknown if the Gestalt rules also apply to tactile or uniquely multimodal stimuli. To investigate these rules, we used lights, touches, and a combination of lights and touches, arranged in a classic Ternus configuration. Three stimuli (A, B, C) were arranged in a row across three fingers. A and B were presented for 50 ms and, after a delay, B and C were presented for 50 ms. Subjects were asked whether they perceived AB moving to BC (group motion) or A moving to C (element motion). For all three types of stimuli, at short delays, A to C dominated, while at longer delays AB to BC dominated. The critical delay, where perception changed from group to element motion, was significantly different for the visual Ternus (3 lights, 162 ms) and the tactile Ternus (3 touches, 195 ms). The critical delay for the multimodal Ternus (3 light – touch pairs, 161 ms) was not different from the visual or tactile Ternus effects. In a second experiment, subjects were exposed to 2.5 min of visual group motion (stimulus onset asynchrony = 300 ms). The exposure caused a shift in the critical delay of the visual Ternus, a trend in the same direction for the multimodal Ternus, but no shift in the tactile Ternus. These results suggest separate but similar grouping rules for visual, tactile, and multimodal stimuli.

Solving the Correspondence Problem within the Ternus Display: The Differential-Activation Theory

Perception ◽  
10.1068/p5670 ◽  
2008 ◽  
Vol 37 (12) ◽  
pp. 1790-1804 ◽  
Author(s):  
Darko Odic ◽  
Jay Pratt
Keyword(s):  
New York ◽  
Correspondence Problem ◽  
Academic Press ◽  
Nearest Neighbour ◽  
Differential Activation ◽  
Ternus Display ◽  
Display Element ◽  
Group Motion ◽  
Activation Theory ◽  
Explanatory Mechanism

The Ternus display produces a bistable illusion of motion: at very short interstimulus intervals (ISIs; < 30 ms) observers perceive element motion while at longer ISIs (> 30 ms) observers perceive group motion. In experiment 1, however, we find that, when the Ternus display's ISI contains an occluding box, group motion is mostly eliminated. These results do not fit the predictions made by the short-range/long-range two-process theory [Braddick and Adlard, 1978, in Visual Psychophysics and Psychology (New York: Academic Press)]. We propose that the differential-activation theory (Gilroy et al, 2001 Perception & Psychophysics63 847–861) accounts for our results. We then extend the differential-activation theory as an explanatory mechanism for the Ternus display in experiment 2 by selectively placing an occluder over the first, second, or third Ternus display element. As predicted by the differential-activation theory, the occlusion of the far-left element produced a normal distribution of group motion increasing with ISI, while the occlusion of the other two elements produced an illusion of occluded elements remaining stationary throughout the display. Furthermore, as predicted by the differential-activation theory, each moving element was assigned to its nearest neighbour, producing, in the case of second and third element occlusion, a novel Ternus display motion illusion where only two out of three elements are perceived as moving.

Potassium-evoked directionally selective responses from rabbit retinal ganglion cells

1996 ◽  
Vol 13 (4) ◽  
pp. 705-719 ◽  
Author(s):  
Ralph J. Jensen
Keyword(s):  
Retinal Ganglion Cells ◽  
Apparent Motion ◽  
Ganglion Cells ◽  
Short Pulse ◽  
Retinal Ganglion ◽  
Null Direction ◽  
Sequence Dependent ◽  
Motion Responses ◽  
A Cell ◽  
Gaba Antagonist

AbstractPrevious studies have shown that directionally selective (DS) retinal ganglion cells cannot only discriminate the direction of a moving object but they can also discriminate the sequence of two flashes of light at neighboring locations in the visual field: that is, the cells elicit a DS response to both real and apparent motion. This study examines whether a DS response can be elicited in DS ganglion cells by simply stimulating two neighboring areas of the retina with high external K+. Extracellular recordings were made from ON-OFF DS ganglion cells in superfused rabbit retinas, and the responses of these cells to focal applications of 100 mM KCl to the vitreal surface of the retina were measured. All cells produced a burst of spikes (typically lasting 50–200 ms) when a short pulse (10–50 ms duration) of KCl was ejected from the tip of a micropipette that was placed within the cell's receptive field. When KCl was ejected successively from the tips of two micropipettes that were aligned along the preferred-null axis of a cell, sequence-dependent responses were observed. The response to the second micropipette was suppressed when mimicking motion in the cell's null direction, whereas an enhancement during apparent motion in the opposite direction frequently occurred. Sequence discrimination in these cells was eliminated by the GABA antagonist picrotoxin and by the Ca2+-channel blocker ω-conotoxin MVIIC, two drugs that are known to abolish directional selectivity in these ganglion cells. The spatiotemporal properties of the K+-evoked sequence-dependent responses are described and compared with previous findings on apparent motion responses of ON-OFF DS ganglion cells.

scholarly journals Binocular Capture: The effects of mismatched Spatial frequency and opposite contrast polarity

2010 ◽  
Vol 10 (7) ◽  
pp. 368-368
Author(s):  
A. Raghunandan ◽  
S. Andrus ◽  
L. Nennig
Keyword(s):  
Spatial Frequency ◽  
Contrast Polarity ◽  
Opposite Contrast

scholarly journals Perception of motion direction in Glass patterns with opposite contrast polarity dots

2004 ◽  
Vol 4 (8) ◽  
pp. 850-850
Author(s):  
M. M. Del ◽  
M. Gori
Keyword(s):  
Motion Direction ◽  
Contrast Polarity ◽  
Opposite Contrast ◽  
Glass Patterns

Contrast Polarity Affects Performance after Figure-Ground Coding

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 243-243
Author(s):  
K J Linnell ◽  
G W Humphreys
Keyword(s):  
Experimental Psychology ◽  
Reaction Times ◽  
Human Perception ◽  
Opposite Polarity ◽  
Regular Polygons ◽  
Target Element ◽  
Dramatic Effect ◽  
Contrast Polarity ◽  
Search Experiment ◽  
Opposite Contrast

Gilchrist et al (1997 Journal of Experimental Psychology: Human Perception and Performance23 464 – 480) proposed that some aspects of grouping are relatively insensitive to variations in contrast polarity between the elements to be grouped. We assessed the contrast-polarity sensitivity of grouping in a visual search experiment. Display elements were corner-brackets arranged at the vertices of regular polygons (see Donnelly et al, 1991 Journal of Experimental Psychology: Human Perception and Performance17 561 – 570), either aligned with polygon sides (strong-grouping condition), rotated through 20° (weak-grouping condition), or rotated through 180° (open condition). The background was grey; on same-contrast-polarity trials, elements were either all white or all black; on opposite-polarity trials, each element was white and black. The task was to detect a target element rotated 180° with respect to the others. With weak grouping present, opposite contrast polarity slowed reaction times dramatically: they were as slow as those to open displays. A second experiment in which display elements were pacmen showed that the contrast-polarity effect on performance is modulated by figure - ground relations: the dramatic effect of contrast polarity in the weak-grouping condition disappeared, presumably because search focused on the uniform grey illusory surface. These results suggest that grouping operates automatically to produce figure - ground coding of displays, but that contrast polarity differences within a figural surface affect the output of these codes to systems concerned with perceptual discriminations.

scholarly journals Perceptual grouping in the Ternus display: evidence for an `association field' in apparent motion

2002 ◽  
Vol 42 (8) ◽  
pp. 1005-1016 ◽  
Author(s):  
David Alais ◽  
Jean Lorenceau
Keyword(s):  
Apparent Motion ◽  
Perceptual Grouping ◽  
Ternus Display

scholarly journals Position acuity with opposite-contrast polarity features: Evidence for a nonlinear collector mechanism for position acuity?

1996 ◽  
Vol 36 (4) ◽  
pp. 573-588 ◽  
Author(s):  
Dennis M. Levi ◽  
Sarah J. Waugh
Keyword(s):  
Contrast Polarity ◽  
Opposite Contrast

scholarly journals Nonsymbolic numerosity in sets with illusory-contours exploits a context-sensitive, but contrast-insensitive, visual boundary formation process

2021 ◽  
Author(s):  
Andrea Adriano ◽  
Luca Rinaldi ◽  
Luisa Girelli
Keyword(s):  
Numerical Representation ◽  
Illusory Contours ◽  
Boundary Formation ◽  
Contrast Polarity ◽  
Context Sensitive ◽  
Visual Boundary ◽  
Brightness Enhancement ◽  
Texture Density ◽  
Numerical Discrimination ◽  
Opposite Contrast

AbstractThe visual mechanisms underlying approximate numerical representation are still intensely debated because numerosity information is often confounded with continuous sensory cues (e.g., texture density, area, convex hull). However, numerosity is underestimated when a few items are connected by illusory contours (ICs) lines without changing other physical cues, suggesting in turn that numerosity processing may rely on discrete visual input. Yet, in these previous works, ICs were generated by black-on-gray inducers producing an illusory brightness enhancement, which could represent a further continuous sensory confound. To rule out this possibility, we tested participants in a numerical discrimination task in which we manipulated the alignment of 0, 2, or 4 pairs of open/closed inducers and their contrast polarity. In Experiment 1, aligned open inducers had only one polarity (all black or all white) generating ICs lines brighter or darker than the gray background. In Experiment 2, open inducers had always opposite contrast polarity (one black and one white inducer) generating ICs without strong brightness enhancement. In Experiment 3, reverse-contrast inducers were aligned but closed with a line preventing ICs completion. Results showed that underestimation triggered by ICs lines was independent of inducer contrast polarity in both Experiment 1 and Experiment 2, whereas no underestimation was found in Experiment 3. Taken together, these results suggest that mere brightness enhancement is not the primary cause of the numerosity underestimation induced by ICs lines. Rather, a boundary formation mechanism insensitive to contrast polarity may drive the effect, providing further support to the idea that numerosity processing exploits discrete inputs.

Perceptual Organization of Apparent Motion in the Ternus Display

Perception ◽  
10.1068/p2941 ◽  
1999 ◽  
Vol 28 (7) ◽  
pp. 877-892 ◽  
Author(s):  
Zijiang J He ◽  
Teng Leng Ooi
Keyword(s):  
Apparent Motion ◽  
Perceptual Organization ◽  
Ternus Display
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