Detection of disparity motion by the human observer.

A single-line stimulus in a context-free visual environment presented for 250 msec needs to move with a disparity velocity of 25 to 45 min of arc/s before the direction of depth motion can be correctly identified. Presence of a pair of flanking line stimuli improves this value severalfold, but even then the threshold is 18 to 28 times higher than for the detection of a static disparity difference.