Movement-Produced Stimulation Is Important in Prism-Induced After-Effects: A Reply to Hochberg

Is Reafference Necessary for Visual Adaptation?

Two studies were performed to determine the necessity of reafference (stimulation due to self-induced movement) in the production of adaptation to prismatic displacement. In Exp. I, 48 Ss exposed to laterally-displacing prisms, were equally divided into four groups comprising combinations of each of the two following variables: self-induced versus passive movement, and self-directed versus externally-directed motion. These groups were non-differential in the magnitude of positive adaptation, although the total population adapted positively and significantly to the prisms. In Exp. II, 17 Ss were tested before and after exposure to the same prisms in a situation which provided informational feedback regarding error and which eliminated self-produced movement. The group demonstrated significant positive adaptation. It is concluded that reafference is not necessary for adaptation and that informational feedback is, at least, sufficient and may be necessary for adaptation.

Adaptation to Prismatically Rotated Visual Fields

The aftereffects of viewing a tilted field of lines differ from the effects of viewing a tilted field of objects. The difference is attributed to the fact that unlike isolated lines, objects have specifiable normal orientations.

Nonvisual Components in Visual Form Perception

Since certain curvature aftereffects require active movements during prismatic adaptation, non-visual components must affect some (but not all) visual shape perception.