Evidence for the persistence of visual guidance information.

An earlier study from our laboratory provided initial support for the hypothesis that information facilitating visual guidance persists in the absence of retinal stimulation. The present study supports and extends this hypothesis with three experiments in which visually occluded subjects positioned a point of light at the location of a previously viewed target and also walked in the direction of a previously viewed path. In both tasks, performance was possible following occlusion, and in all cases, performance slowly and significantly decreased with longer durations of occlusion. This decay in performance was gradual and had a "half-life" of greater than 15 sec. Absolute performance was correlated across tasks. The effect of occlusion on absolute error in the localization performance was relatively stable within individuals over a 3-week period. The biological utility of guidance information persistence is discussed along with implications for space constancy, illusions of motion, and problems of disorientation.