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Pascal Mamassian; Auditory tones influence perceived speed in apparent motion. Journal of Vision 2005;5(8):877. doi: 10.1167/5.8.877.
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© ARVO (1962-2015); The Authors (2016-present)
Several cross-modal studies show an interaction when two modalities provide converging evidence for a given attribute, for instance an estimate of spatial location in the ventriloquist effect. Which modality dominates depends on the reliability of each modality for that particular attribute. For a stimulus that varies across both space and time, we therefore anticipate that vision will have a predominant role over its spatial properties and audition a predominant role over its temporal properties. We tested this prediction on the perceived speed of an apparent motion display in presence of fluttering tones. We hypothesized that the temporal frequency of the auditory signal could influence the perceived temporal frequency of the visual display, and in turn affect its perceived speed. Visual stimuli were two Gabors presented on either side of the fixation cross, moving in opposite directions (either inwards or outwards). The spatial envelope stayed stationary and the motion was produced by shifting the carrier's phase by 90deg at a rate of 19Hz. This visual display was presented simultaneously with a fluttering sequence of tones at a rate of 16 or 22Hz. Observers had to decide whether this bimodal stimulus appeared to move faster or slower than a purely visual stimulus whose phase was varied between trials. The point of subjective equality was taken as a measure of the perceived speed of the bimodal stimulus. The rate of the auditory tones influenced the perceived speed of the visual display: the slow auditory rate slowed down the perceived speed, and the fast rate accelerated it. These results suggest that the integration between auditory and visual temporal signals occurs before the estimation of speed.
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