Reversed Depth from Positive and Negative Stereograms

Abstract

A stereogram was presented with patterns of opposite contrast–one positive the other negative. One eye received only the positive pattern; the other received both positive and negative patterns superimposed. Subjects reported apparent reversals of perceived depth: crossed (convergent) disparity made the fused stereogram appear further away, whilst uncrossed (divergent) disparity made it appear nearer. It is believed that spatial summation in the visual system blurs the superimposed positive-and-negative contours and shifts their effective positions, leading to reversals in perceived disparity.