Aim: To investigate whether or not we need binocular single vision (BSV) for successful depth perception.
Methods: A mixed-measures design was used to compare monocular subjects and binocular subjects in their ability to judge depth. Experimental stimuli were images resembling large drawing pins that were displayed on a computer screen. Subjects had to adjust the spike of the drawing pin, by means of a keypad, until it appeared to be at an angle of 90° to the head of the pin. The head of the drawing pin was at a slant of 30° from the frontal plane, around either the horizontal or vertical axis. The computer recorded the number of degrees away from the 90° position that the spike was set, the time taken and the standard deviation of the settings. A three-factor mixed measures ANOVA was used to analyse the results.
Results: Overall, binocular subjects were more accurate than monocular subjects (F = 13.894, df = 1, 14, p < 0.01) in judging when the spike was set at an angle of 90° to the head of the pin. There was no significant difference between the horizontal or vertical orientations of stimuli in terms of accuracy (F = 1.250, n.s.), or between the two groups in the time it took them to complete the task.
Conclusion: BSV is advantageous and the time and resources spent on restoring and maintaining BSV are worthwhile.