Anti-Glass patterns and real motion perception: same or different mechanisms?

A sequence of anti-Glass patterns, composed by dot pairs with opposite luminance polarity, elicits a clear perception of motion in the direction of the white dot of the pair. This effect can be reversed by introducing a delay in the presentation of white dots, suggesting a faster processing of light dots as a cause of the motion signal (M. M. Del Viva, M. Gori, & D. C. Burr, 2006). If this hypothesis is correct, anti-Glass patterns should interact with real motion signals. In this study, we compare the motion induced by these stimuli to test whether they are analyzed by the same motion mechanism. We found that motion induced by anti-Glass patterns annuls real motion, when they are presented simultaneously in the same display and moving in opposite directions. By lowering the contrast of one of them, motion toward the stimulus with higher contrast prevails. We also found sub-threshold summation of motion induced by anti-Glass patterns and real motion, when presented simultaneously and moving in the same direction. These findings indicate that anti-Glass patterns and moving stimuli are processed by the same, contrast-dependent motion mechanism and lend further support to the proposed explanation of the effect.