An Illusion That Avoids Focus

Fixation of certain high contrast patterns may produce an intriguing visual phenomenon of movement in the periphery of the stimulus. Controversy exists over whether the illusory motion is produced by braingenerated activity or by the accommodation system. We provide a review of the literature to demonstrate that neither of these hypotheses is satisfactory and that the illusion, together with the conflicting empirical evidence that surrounds it, may be explained by the normal instability of human gaze.