Perceiving self-motion in depth: the role of stereoscopic motion and changing-size cues

During self-motions different patterns of optic flow are presented to the left and right eyes. Previous research has, however, focussed mainly on the self-motion information contained in a single pattern of optic flow. The current studies investigated the role that binocular disparity plays in the visual perception of self-motion, showing that the addition of stereoscopic cues to optic flow significantly improves forwards linear vection in central vision. Improvements were also achieved by adding changing-size cues to sparse (but not dense) flow patterns. These findings showed that assumptions in the heading literature that stereoscopic cues only facilitate self-motion when the optic flow has ambiguous depth ordering, do not apply to vection. Rather, it was concluded that both stereoscopic and changing-size cues provide additional motion in depth information which is used in perceiving self-motion.