The Role of Optical Expansion Patterns in Locomotor Control

Patterns of optical expansion during approach to a surface were simulated, and 20 men were asked to locate the focus of that expansion under different conditions. Errors were less when the pattern was framed and when the visual field was small. Further, the subjects located the focus with any real confidence and accuracy only at the fastest expansion rate (i.e., .5 sec before theoretical surface impact), which casts doubt on J. J. Gibson's hypothesis of the importance of the focus of expansion in locomotor control.