Display duration and stereoscopic depth discrimination

We investigated the role of display duration in stereoscopic depth perception. The display consisted of a dynamic random-dot stereogram, with two disparity-defined squares (1.9 degrees x 1.9 degrees), one on the left and one on the right of a central (Nonius) fixation stimulus. The sign of the disparity (crossed or uncrossed) was always the same for both squares, and the magnitude of disparity was 0.25 degree for one square and either 0.125 degree or 0.375 degree for the other square. Participants indicated which square appeared closer. The display duration was varied adaptively between 20 and 1000 ms until participants performed at 75% accuracy. Results confirmed large individual differences in the display duration required for stereoscopic depth perception. Approximately half of the 100 naive participants were able to perform the task at 20 ms, while the remaining participants required up to 1000 ms to perform at criterion. The present study shows that display duration is a critical variable in explaining wide differences in reported abilities of individuals to process stereoscopic depth information.