Properties of binocular and spatial vision of the rhesus monkey

A series of experiments were undertaken to investigate, using psychophysical techniques, binocular and spatial resolution properties of the rhesus monkey. Using random dot stereogram stimuli to investigate both sensory and motor aspects of binocular vision, it was found that these properties are very much like those of man. Assessment of the monkey’s stereothresholds revealed several important findings: 1) The stereothreshold of the monkey varies as a function of viewing duration in a way similar to man's, 2) Random dot stereogram stimuli appear to be detected by two types of stereopsis, patent stereopsis below 30 min of arc disparity and qualitative stereopsis above this value, 3) Several monkeys and most human subjects had better detection of crossed disparities than uncrossed disparities. Investigations into the monkey's fusional vergence ranges' showed that man and monkey have approximately the same fusional vergence abilities. The contrast sensitivities of monkey and man were studied through investigating the oblique effect. These studies revealed, for the first time, an animal other than man which possesses this phenomenon. Additionally it was found that the oblique effect exists at suprathreshold contrasts, a property not previously known. The results of these experiments support the use of the monkey as a model of the human visual system for the processes of binocularity and spatial resolution.