A new visual illusion of relative motion.

We present a remarkably simple illusion that manifests whenever a certain class of flat static patterns are moved across our peripheral visual field. A relative motion is perceived in a direction perpendicular to the true motion. Translatory, looming, and rotational movements of the head or the pattern can all elicit it. Each pattern is constructed of simple elements that define, through luminance, an orientation polarity. This polarity could be encoded by spatiotemporally tuned, orientation sensitive units in area V1. We offer an explanation for the illusion based on how such units from V1 may be combined to feed the processes that subsequently interpret motion.