Perceptual asynchrony of motion and colour

When a green pattern moving upwards and a red pattern moving downwards alternates with the indicated time course, it is hard to judge which colour and direction are shown together (left movie). For motion and colour to be seen in phase, the direction change has to lead the colour change by about 100 ms for an inter-change interval of 250 ms (left movie).

(a) Stimulus structure

(b) Conventional account of the apparent motion delay in terms of perceptual processing lag [1]. Motion takes longer to be consciously perceived than colour.

(c) New account in terms of time markers [2]. Marker flags indicate transitions (first-order temporal changes) in the two sequences. The observers cannot perform the required task to match direction reversals with colour transitions due to difficulty in detecting the time of direction reversals (turning points / second-order temporal changes) at rapid alternations. This account is based on the finding that an apparent delay of changes in motion direction occurs only for rapid alternations, and this delay is not accompanied by a difference in reaction time. We also found that perceptual asynchrony depends on the temporal structure of the stimuli (transitions vs turning points), rather than the attribute type (colour vs. motion).

[1] K. Moutoussis and S. Zeki, "A direct demonstration of perceptual asynchrony in vision," Proc R Soc Lond B Biol Sci, vol. 264, pp. 393-9, 1997.

[2] S. Nishida and A. Johnston, "Marker correspondence not processing latency determines temporal binding of visual attributes," Current Biology, vol. 12, 2002.