Stereo visual cues help object motion perception during self-motion

Abstract

Recent studies have suggested that the visual system subtracts the optic flow pattern experienced during self-motion from the projected retinal motion of the environment to recover object motion, a phenomenon called 'flow parsing' (Warren and Rushton, 2007 Journal of Vision7(11) 2, 1-11). In this experiment, we tested how adding stereo visual cues to help accurate depth perception of a moving object relative to the flow field affected the flow parsing process. The displays (26°x26°, 500ms) simulated an observer approaching a frontal plane that was composed of 300 randomly placed dots. A red probe dot moved vertically over this plane or over the image plane of the projection screen through a midpoint at 3° or 5° eccentricity. A horizontal component (along the world X-axis) under control of an adaptive staircase was added to the probe dot's vertical motion to determine when the probe motion was perceived as vertical. Participants viewed the display with and without stereo visual cues. We found that with stereo visual cues, flow parsing gains were significantly higher when the probe moved over the frontal plane, but significantly lower when it moved over the screen surface. We conclude that stereo visual cues help veridical perception of object motion during self-motion.