Study of unaided cross-eyed stereopsis

The learning of the skill of unaided cross-eyed stereopsis was investigated on a group of young adults. Both pictorial and random-dot stereograms were used; small stereograms were viewed at normal reading distance and large projected stereograms were viewed in an auditorium. The results suggest that this direct stereoscopic technique can be learned within a few minutes by almost everyone in the population represented by the test group. The calculated eye-convergence angles for various conditions of cross-eyed stereoscopic viewing indicate that little eye discomfort is caused by this factor when the stereograms are located at a sufficient distance from the viewers. The comments of subjects support this conclusion. The unexpected prevalence of the aptitude for this skill should have practical application in the unaided three-dimensional visualization of computer-generated stereograms.