The detection of motion in chromatic stimuli: first-order and second-order spatial structure

This study provides evidence for the existence of a low-level chromatic motion mechanism and further elucidates the conditions under which its operation becomes measurable in an experimental stimulus. Observers discriminated the direction of motion of amplitude modulated (AM) gratings that were defined by luminance or chromatic variation and m asked with spatiotemporally broadband luminance or chromatic noise. The size and retinal location of the stimuli were varied and the effects of broadband noise and grating masks were both compared with the cohort of stimuli. Some significant disparities in the published literature were well explained by the results. In conclusion, evidence for a chromatically sensitive motion mechanism that evades the detrimental effects of a luminance mask was found only at the fovea and only when the stimulus was small and centrally placed. (C) 2004 Elsevier Ltd. All rights reserved.