Crowding affects flicker motion aftereffect more than static motion aftereffect

Purpose; A target embedded in multiple distractors is difficult to detect. This crowding effect is likely due to the inability of spatial attention to resolve individual items. The flicker motion aftereffect (MAE) is thought to be mediated by an attention based motion mechanism. In this study we tested whether the flicker MAE is more affected by crowding than the static MAE. Methods; Observers adapted to a circular patch containing a moving grating. This patch was embedded in an array of five similar grating patches. Each grating moved independently, in one of two possible directions. The group of five grating patches was oriented either radially (severe crowding effect) or tangentially (little crowding effect) relative to the point of fixation. The duration of the MAE for a counterphase flickering grating or for a static grating was measured. Results: For the counterphase flickering test grating, the duration of the MAE was much longer when there was little crowding (tangential) than when there was severe crowding (radial). However, for the static test grating, the difference in MAE durations was much less. Conclusions: Our results support the claims that crowding results from insufficient attentional resolution, and attention contributes significantly to the flicker MAE.