Is Reafference Necessary for Visual Adaptation?

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Abstract
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.