The roles of target and eye motion in the production of the visual shift in prism adaptation.

Abstract

Two experiments, with a total of 48 Ss, were performed to evaluate the possible determinants of the visual shift (VS) in prism adaptation. In Experiment 1 the effects of target movement and pursuit eye movements on resultant visual adaptation were investigated. Maximal VS was produced when both of these conditions were present. Experiment 2 was conducted to determine whether hypnotic anesthesia in and around the eyes and eye muscles reduces feedback from eye-position sensations and, consequently, the magnitude of the VS. This manipulation proved to be successful and virtually eliminated the production of VS. The results of the two experiments helped to identify two factors that contribute to the production of the VS: the presence of visual target movement during prism exposure and the accompanying eye movement which produces a change in the felt position of the eyes during target tracking.