Stereopsis from reversible and irreversible patterns

Eight subjects reported stereoscopic depth as a function of the magnitude and direction of disparity carried by a reversible grid or an irreversible solid surface. The former alternated between a diamond seen against a grating or a uniform rectangular grid pattern with stereoscopic depth reported only when the diamond was perceived. Depth was attenuated for the grid compared to the solid surface patterns. Disparity can be defined by perceptually extracted forms with depth present only when those forms are bounded by visible contours.