Fast perception of binocular disparity

Abstract:

Is depth perception from binocular disparities—stereopsis—slow or fast? Rapidly changing disparities are perceptually difficult to track, which suggests that stereopsis is generally slow, but the wide-spread belief in the slowness of stereo does not have good empirical support. Classic experiments in which stereo occurred slowly are difficult to interpret. We compared speed-accuracy tradeoff functions (SATFs) between two forced-choice discriminations: one based on stereoscopic depth, and one based on luminance. Unexpectedly, both SATFs deviated from chance levels of accuracy at the same response time—approximately 200 ms—with stereo accuracy increasing, on average, more slowly than luminance accuracy after this initial delay. Thus, the initial processing of disparity for perceived depth took no longer than the initial processing of luminance for perceived brightness. Stereoscopically defined surface slant was similarly apparent soon after stimulus presentation. This finding, that binocular disparities are available early during visual processing, means that depth is perceived quickly, and intriguingly, those disparities may be more widely important for everyday visual function than previously thought.

http://poseidon.sunyopt.edu/Backuslab/