Gibson's invariance hypothesis and the Ames oscillatory effect.

Previous explanations of the Ames oscillatory effect are evaluated by means of a functional-evolutionary theory of perception. Use of stored interpretations, static elements, and other explanatory ideas are rejected in favor of adaptive response to ambiguity as the essential factor for the effect. It is emphasized that Ss report perception of rotation, oscillation, reversal, and flapping, which are all correlates of horizontal contraction and expansion of the retinal image, when viewing rotating objects. The provision of all possible correlates of the transforming array is described as supportive of a functional-evolutionary approach, and Gibson's theory of perception.