Visual feedback, distribution of practice, and intermanual transfer of prism aftereffects.

Abstract

These experiments tested the hypothesis that intermanual transfer of prism aftereffects depends on both the type of visual feedback provided to the observer and the distribution of practice during the antecedent prism-wearing session. In Exp. I, 8 Ss reached for a visible target that they viewed through prisms. They responded for 60 trials at rates of 3, 6, 12, 24, and 48 times per minute, viewing the reaching hand only after each trial was completed (terminal visual feedback). Measures of coordination were taken both before and after exposure, and shifts in coordination were used as measures of the aftereffects. With increased rates of responding, the magnitude of intermanual transfer significantly decreased, but the magnitude of the aftereffects in the reaching hand remained unchanged. In Exp. II, 9 Ss responded for 60 trials at rates of 6, 12, and 24 times per minute, viewing the reaching hand through the prisms at all times (continuous visual feedback). Although aftereffects were obtained with the reaching hand, no significant transfer resulted. Results suggest prism-adapted Ss attain different end-states, depending on the specific antecedent exposure conditions, and any description of the mechanism underlying prism aftereffects must be restricted to the particular conditions under which the aftereffects were generated.