Stereopsis and the representation of space.
Four stereoblind and four normal subjects were tested on a mental rotation task. It was hypothesized that, if stereopsis is an important input for building up the perceptual system that represents three-dimensional space, then subjects lacking it ought to be deficient  at mental rotations in depth. Stereoblind subjects were equally efficient at picture-plane and depth rotations, and were nonsignificantly better than normal subjects at rotations in depth. It was concluded that in the absence of stereopsis other cues are sufficient for the development of the "three-dimensional" perceptual system. A puzzling paradox was raised, however, by the finding that the introspections of the two groups differed markedly.
D003867:Depth Perception; D005556:Form Perception; D006801:Humans