The Neural Control of Vision
L. The Processing of Depth

Figure 59 presents data obtained from a monkey in which the animal was trained to either detect the appearance of a single target in various locations or to discriminate that target from three other identical targets that appear at a lesser depth. In each case the degree of depth cues provided was varied as indicated on the X axis. The stimuli were presented under three conditions: stereo cues only, parallax cues only, and both cues together. As can be seen the monkey did quite well for all these conditions, showing a general improvement when disparity and parallax cues were increased. Performance was best and had the shortest latencies when both stereo and parallax cues were presented together in harmony. This was true both for the detection and discrimination tasks. The longest reaction times occurred when only parallax cues were provided. Maximizing speed of processing is of course of prime importance in the world fraught with predators and other dangers.