Perception of synchrony between auditory and visual stimuli.

Abstract

The literature has fairly consistently reported a difference in how well humans perceive synchrony depending on the order of auditory and visual stimuli. When the auditory stimulus occurs first and the visual stimulus follows, subjects are more sensitive and so perceive asynchrony with smaller time delay between the stimuli. On the other hand, when the auditory follows the visual stimulus, the subjects are more tolerant and perceive stimuli with larger time delays as synchronous. Thresholds of synchrony perception in these two conditions are thus asymmetrical. The present study attempts to test the Lewkowicz Model, by which the asymmetrical thresholds are explained as a result of arrival-time differences between auditory and visual stimuli to the brain, such that visual stimulus takes longer in processing to be perceived versus auditory one. Reaction-times to these stimuli were measured to determine the arrival-time difference and plotted with synchrony perception. On the basis of Lewkowicz Model we predicted that reaction-time difference between the two stimuli correlate with subjective synchrony. The results did not support the Lewkowicz Model. The expected tendency of 30--40ms of subjective synchrony was not shown. The subjects took, in average, only 7.7ms to detect asynchrony when the auditory stimulus followed the visual stimulus. That the subjects did not tolerate greater temporal gap when the auditory followed versus when it preceded the visual stimulus was a very different result from majority of previous studies. Different factors in perceiving synchrony are discussed in this paper, as well as the application of the research in telecommunications.