Perceptual asynchronies for biological and non-biological visual events.
Four experiments investigated the hypothesis that different attributes of a visual scene are processed by independent channels working asynchronously. Experiment 1 considered the attributes of colour, form, and movement of simple geometrical configurations. In each of three conditions, two of these attributes switched simultaneously between two fixed values (Green/Red, Circle/Square, Fixed/Moving). Participants indicated which of the two attributes changes was perceptually closer in time to a sound signal. Response probabilities varied as a function of the time of occurrence of the sound, showing that the processing of the movement channel is delayed with respect to the other two. A smaller but significant difference was also detected between the processing times for colour and form. Comparing Experiments 1 and 2 showed that movement velocity does not affect the delay with which movement onset is perceived with respect to colour. Experiment 3 contrasted colour and movement in the perception of a biological movement. The stimuli were video clips of a coloured ball being lifted by a hand. The colour of the ball changed a variable amount of time before or after the ball started moving. Participants indicated which of the two changes had occurred first. We found that, unlike in Experiments 1 and 2, movement perception no longer lagged colour perception. Experiment 4 tested the hypothesis that the disappearance of the asynchrony is due to perceptual anticipation. We discuss the implications of the results vis-à-vis current theories on perceptual binding and on the coding of dynamic events.
Aymoz
Christelle
C
Department of Psychbiology, Faculty of Psychology and Educational Sciences, University of Geneva, UNI MAIL 40 Boulevard du Ponts d'Arve, CH-1211 Geneva 4, Switzerland.
Viviani
Paolo
P
D000293:Adolescent; D000328:Adult; D003118:Color Perception / Q000502:physiology; D005260:Female; D005556:Form Perception / Q000502:physiology; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology; D011601:Psychophysics; D014796:Visual Perception / Q000502:physiology*