Stereopsis impairment in apparently moving random dot patterns

Abstract

A moving random-dot pattern was stereoscopically partitioned into a static vertical cyclopean depth grating. The dots were horizontally displaced across the grating in repeated uniform jumps. Stereopsis and movement perception were examined at stimulus angular velocities in the range of 0.1°-44°/sec. At 1°-5.5°/sec the depth perception of the grating was strongly impaired: that is, depth judgment for suprathreshold disparities was poor and the stereo-acuity threshold was elevated. The effect of varying the cyclopean spatial frequencies (CSFs)between 0.3 and 4.2 cpd was also examined. Although there was no strong dependence on CSF, the impairment was more pronounced at CSFs greater than 1.3 cpd. When smooth tracking eye movements were absent, that is, during fixation or saccadic scan, stereoscopic depth was not impaired. Eye movement measurements indicated that this phenomenon is associated with optokinetic nystagmus (OKN). It is suggested that the impairment in resolving depth in this particular spatiotemporal configuration actually reflects a temporal limit of the stereoscopic system, which is manifested during OKN. © 1987 Psychonomic Society, Inc.