Asynchronous processing in vision: Color leads motion

It has been demonstrated that subjects do not report changes in color and d irection of motion as being co-incidental when they occur synchronously. In stead, for the changes to be reported as being synchronous, changes in dire ction of motion must precede changes in color. To explain this observation, some researchers have suggested that the neural processing of color and mo tion is asynchronous. This interpretation has been criticized on the basis that processing time may not correlate directly and invariantly with percei ved time of occurrence. Here we examine this possibility by making use of t he color-contingent motion aftereffect. By correlating color states disprop ortionately with two directions of motion, we produced and measured color-c ontingent motion aftereffects as a function of the range of physical correl ations. The aftereffects observed are consistent with the perceptual correl ation between color and motion being different from the physical correlatio n. These findings demonstrate asynchronous processing for different stimulu s attributes, with color being processed more quickly than motion. This sug gests that the time course of perceptual experience correlates directly wit h that of neural activity.