PURPOSE: To examine experimentally whether color vision deficiency confers a selective advantage under scotopic conditions. METHODS: Red-green color-deficient subjects, monochromats, and age-matched color-normal control subjects were examined. In each subject the time course of dark adaptation, scotopic visual field sensitivity, and performance on a scotopic perceptual task were measured. RESULTS: No significant differences were found between red-green color-deficient subjects and control sub...