Reversals of Visual Depth Caused by Motion Parallax

The role of the velocity and direction of retinal movement in the determination of apparent depth from motion parallax was examined. Motion parallax was produced either by linking the movement of random-dots to head movement or by making this motion independent of the head movement. The results show that apparent depth was largely estimated from the velocity difference between the stimuli. The direction of retinal movement in the absence of head movement did not determine whether the pattern appeared to protrude or recede. Information about direction linked to head movement was able to stabilize protrusion/recession by providing a cue for the location of the fixation point. Depth reversal occurred less frequently in the presence than in the absence of head movement. When the fixation point shifted from the apparently protruding pattern to the apparently receding pattern, in both the presence and absence of head movement, depth reversal was readily observed.