Deficits in stereoscopic depth perception by mildly mentally retarded adults.

The ability of mildly mentally retarded adults to perceive specific perceptual phenomena attendant to global stereopsis produced by random element stereograms was investigated. From the standpoint of computational vision, these phenomena are difficult to process, yet nonretarded persons perceive them effortlessly and without error. Retarded subjects in this study, however, exhibited large qualitative deficits not attributable to an absence of stereopsis or a failure to comprehend. These results suggest that the computational requirements of the stimuli exceeded resources and imply the presence of a substantial structural deficit in an automatic preattentive perceptual stage quite distant from the domain of cognition.