Visual guidance of locomotion

Argues that guidance situations requiring accuracy involve locomotion toward a specific target. The perceptual information for this guidance is provided by (a) the movement of the target, (b) the presence and nature of any drift signaling the presence of a heading error, and (c) the nature of the correction required. Rejection of expansion-information judgments as the probable basis of guidance is based on the lack of response variation with variation of the stimulus display (at times extreme) and the high degree of inaccuracy consistently displayed. A total of 140 undergraduates participated in 5 experiments to test this theory. No improvements in accuracy occurred with (a) variation of the viewing conditions, nature of the displays, and nature of the task; or from (b) the use of monocular or binocular vision, free viewing or fixation, sophisticated ss, and extensive instruction on the nature of the expansion pattern. By comparison, the detection of target drift was affected by stimulus variation, the presence of an expanding background reducing efficiency of detection. Accuracy of cancellation of target drift varied with stimulus variation but remained at a level of accuracy superior to that of judgments based on expansion information.