Perceptual pairing of colour and motion.

Observers often pair colours with earlier periods of motion. This observation has prompted the proposal that changes in colour are processed faster and perceived as occurring before physically coincident changes in direction--a brain-time account. Alternatively, it has been proposed that the sudden onset of a surface, or a direction reversal within a persistent surface, can trigger an analysis that determines the perceptual properties of the surface. Hypothetically, this analysis persists for some period of time and the consequences are perceived as having occurred when the analysis commenced--a post-dictive account. Hypotheses based upon these alternate accounts are contrasted in a series of experiments. It is shown that the optimal conditions for pairing specific combinations of colour and motion arise when colour changes are delayed relative to direction changes. In these conditions observers can pair more rapid oscillations of colour and motion and perceptual pairings are more systematic relative to when the changes in colour and direction are physically synchronous. It is also shown that, when pairing colour and motion, the sudden onset of a moving surface does not have the same consequences as a direction reversal within a persistent surface. These findings are consistent with the brain-time, but are inconsistent with the post-dictive, account of perceptual asynchrony.