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Katherine McArthur, Pascal Mamassian; Temporal dynamics of bistability in motion transparency. Journal of Vision 2005;5(8):701. doi: 10.1167/5.8.701.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptual reversals occur when a given stimulus is consistent with more than one possible percept. When viewing motion transparent stimuli, observers experience reversals in depth. We are interested in the dynamics of these reversals, and particularly the role of segregation processes in determining biases and reversal rates. Random-dot kinematograms were generated and presented as two distinct surfaces moving at the same speed in opposite horizontal directions. We designed an experiment with two conditions varying the ease of segregation. In the first condition both surfaces were composed of only black dots, while in the other condition the two surfaces were distinguished using black and white dots. Critically, motion is necessary to perceive two surfaces in the same contrast condition since no other segregation cues are available. The task of the observers was to report the trajectory of the surface that appeared in front, by responding either left or right every two seconds. Consistent with previous studies (Mamassian and Wallace, VSS '03), directional biases varied across participants. In spite of these idiosyncrasies, the initial bias was stronger when the two surfaces had the same contrast. Observers were, however, more likely to experience depth reversals when the two surfaces had the same contrast. These results suggest that the role of segregation cues changes throughout a trial: segregation cues appear to accentuate directional biases initially, but then facilitate perceptual reversals.
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