Colour, form, and movement are not perceived simultaneously.
Behavioural, neuro-anatomical and clinical evidence suggests that different aspects of the visual scene are processed separately, but the extent to which the processing is carried out along segregated and independent parallel pathways is still debated. Moreover, it is also unclear whether these aspects are processed at the same rate, and their neural correlates reach consciousness at the same time. An experiment investigated this issue in the case of three attributes of 2D displays: colour, form, and movement. There were three conditions, one for each possible pairing of these attributes. Stimuli were combinations of two values for each attribute (red/green, circle/square, fixed/moving). In each condition the stimuli changed twice in close temporal succession, each attribute switching asynchronously between the two possible values. The observer's task was to report which change had occurred first. Response probabilities were computed for 13 values of the asynchrony, and transformed into estimates of perception time with the help of a psychophysical model. The results showed that colour and form are processed almost simultaneously. By contrast, movement perception is delayed by about 50 ms. The implications of these findings vis à vis the so-called perceptual binding problem are discussed.
Viviani
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P
Department of Psychobiology, Faculty of Psychology and Educational Science, University of Geneva, 40 Bd du Pont d'Arve, 1205 Geneva CH, Switzerland.
Aymoz
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C
D000704:Analysis of Variance; D003118:Color Perception / Q000502:physiology*; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D016011:Normal Distribution; D011601:Psychophysics; D011930:Reaction Time