Direction in the color plane as a factor in chromatic flicker and chromatic motion

A percept of motion results when a chromatic grating, formed from a spatial alternation between two isoluminant hues, drifts across the visual field. With hue pairs chosen to be equally subjectively dissimilar, the motion is greater for alternation along some directions in color space (orange/blue) than others (green/purple), suggesting a specific interaction between the (L-M) and S(0) chromatic opponent channels. This phenomenon was explored systematically by choosing 24 pairs of hues across the color circle and using the method of paired comparisons to scale their movement-inducing contrast. The flicker-inducing contrast observed from rapid alternation between the pairs was measured in the same way. Both phenomena consistently drew upon both chromatic channels, though in different proportions, as if chromatic and temporal variation information are multiplexed along motion-processing pathways. Border-distinctness data were also collected to isolate the (L-M) channel.