Pattern and depth discrimination from random dot stereograms

The discrimination of depth and pattern was investigated using random dot stereograms. For all four subjects, the psychometric function for depth judgments (probability of correct response) was clearly superior to pattern judgments over a range of ten crossed or uncrossed binocular disparity values. Degrading the visual images, either monocularly or binocularly, with various convex lens power (fogging lenses) reduced both depth and pattern discrimination across all disparity values, rather than simply increasing the thresholds. The results are discussed with reference to current theories of stereopsis, and the question of the hierarchial processing of depth and pattern information is considered.