Abstract
Transparent motion can result in bistable percepts because of an ambiguity about which surface is in front and which one is behind. Previous work has shown that observers have an idiosyncratic bias for perceiving one particular direction of motion in front (Mamassian & Wallace, VSS'03) and that segregation cues, such as contrast, can influence the temporal dynamics of the alternation of which surface is perceived in front (McArthur & Mamassian, VSS'05). Here, we looked at the effect of adaptation to motion in depth (Anstis & Harris, 1974) on an observer's bias for transparent motion. On both pre- and post-adaptation sessions, observers were presented with brief random-dot kinematograms (RDKs) where two transparent planes were displayed in the zero-disparity plane. Their task was to report the direction of motion of the plane perceived in front. In the adaptation period, observers were presented with an RDK that alternated between leftward motion in front and rightward motion behind. To prevent eye movements, two such movies were presented out of phase, above and below fixation. We found that observers' biases for which direction of motion moved in front were different between the pre- and post-adaptation sessions, in a manner mostly consistent with a depth contingent motion aftereffect. These results emphasize the critical role of neural structures sensitive to both motion and binocular disparity in the perception of motion transparency.