Abstract
Bistability arises under prolonged observation of ambiguous figures, leading to sudden and unavoidable changes in perception even though the stimulus remains unchanged. There is a considerable inter-individual variability in the switch rates for any bistable stimulus. Moreover, recent evidence suggests that switch rates for some forms of perceptual bistability are correlated, but not for others. Such correlation patterns are noteworthy as they provide a foothold for identifying neural mechanisms that are shared among clusters of bistability phenomena. One correlated cluster is formed by Necker cube (NC), binocular rivalry (BR) and moving plaids (MP). This suggests a shared mechanism between those forms of bistability, and in previous work we hypothesized this mechanism to be related to surface representations. In the face of that hypothesis it is surprising that structure-from-motion rivalry (SFM) does not correlate with the cluster, even though it centrally involves surface representations as observers perceive the front and back surfaces of a rotating 3D object moving over one another. Here we investigate whether the presence of 3D rotation can cause a stimulus to give rise to a categorically different form of bistability, in which ambiguity in 3D motion, not in surface segmentation, drives perceptual dynamics. To this end we constructed a rotating Necker Cube (rNC), which has the spatial properties of NC and the added property of rotation. In a battery that included all relevant bistable stimuli, we replicate the published correlations among NC, BR and MP as well as the lack of correlation between this cluster and SFM. Critically, we observe a lack of correlation between that cluster and rNC. Since the only difference between NC and rNC is the added property of 3D rotation, the results support the idea that even when surface layout is ambiguous, motion processing mechanisms dictate perceptual dynamics for rotating objects.