Illusory motion reversals and feature tracking analyses of movement.

Abstract

Illusory motion reversals (IMRs) can happen when looking at a repetitive pattern of motion, such as a spinning wheel. To date these have been attributed to either a form of motion aftereffect seen while viewing a moving stimulus or to the visual system taking discrete perceptual snapshots of continuous input. Here we present evidence that we argue is inconsistent with both proposals. First, we show that IMRs are driven by the adaptation of nondirectional temporal frequency tuned cells, which is inconsistent with the motion aftereffect account. Then we establish that the optimal frequency for inducing IMRs differs for color and luminance defined movement. These data are problematic for any account based on a constant rate of discrete perceptual sampling. Instead, we suggest IMRs result from a perceptual rivalry involving discrepant signals from a feature tracking analysis of movement and motion-energy based analyses. We do not assume that feature tracking relies on a discrete sampling of input at a fixed rate, but rather that feature tracking can (mis)match features at any rate less than a stimulus driven maximal resolution. Consistent with this proposal, we show that the critical frequency for inducing IMRs is dictated by the duty cycle of salient features within a moving pattern, rather than by the temporal frequency of luminance changes.