The impact of retinal motion on stereoacuity for physical targets.

In a series of studies using physical targets, we examined the effect of lateral retinal motion on stereoscopic depth discrimination thresholds. We briefly presented thin vertical lines, along with a fixation marker, at speeds ranging from 0 to 16 deg·s-1. Previous investigations of the effect of retinal motion on stereoacuity consistently show that there is little impact of retinal motion up to 2 deg·s-1, however, thresholds appear to rise steeply at higher velocities (greater than 3 deg·s-1). These prior experiments used computerized displays to generate their stimuli. In contrast, with our physical targets we find that stereoacuity is stable up to 16 deg·s-1, even in the presence of appreciable smearing due to visual persistence. We show that this discrepancy cannot be explained by differences in viewing time, prevalence of motion smear or by high frequency flicker due to display updates. We conclude that under natural viewing conditions observers are able to make depth discrimination judgements using binocular disparity signals that are rapidly acquired at stimulus onset.