Binocular summation: a study of contrast sensitivity, visual acuity and recognition

Monocular and binocular sensitivities have been compared previously, mainly by consideration of the absolute threshold. The limited number of studies which has considered tasks such as detection of a contrast gradient and ability to resolve spatial detail has been concerned primarily with photopic levels of illumination. The present study takes the tasks of (1) contrast detection, (2) visual acuity, and (3) recognition, and compares binocular with monocular sensitivities over a wider range of luminances than has been considered before. Maximum summative effects have been found in the contrast domain, and it appears that summation is reduced in situations where the available accommodative-vergence cues are weak.