Unexpected auditory and visual events speed up binocular rivalry

Amanda Parker, Dept. of Psychology, University of Sydney

Abstract
Binocular rivalry is the fluctuation of visual awareness between discrepant images presented to each eye. Subjects (N=5) tracked alternations between orthogonal gratings under three conditions: periodic luminance flicker, random luminance flicker, and no flicker. Flicker sped up rivalry: average dominance period was 0.49s for random flicker, significantly shorter than for an equivalent number of periodic transients (1.57sec), which was significantly shorter than for no flicker (ie, regular rivalry: 2.34s). This result was seen both when luminance transients appeared in an annulus surrounding the rivalling gratings (N=4, random: 0.49s; periodic: 1.19s; no flicker: 1.56s), and also when auditory transients (500Hz beeps) were used (N=4, random: 0.47s: periodic: 1.25s: no beep: 1.98s). The bimodal nature of the effect suggests that a process more global than visual timing is at work, such as supramodal attention to novel ‘events’, or a distortion in timing mechanisms that may count events as part of a time estimation process. The latter possibility is supported by observers’ subjective reports that the alternation rate in the random event condition did not appear faster than normal rivalry (despite the nearly 5-fold change), indicating a very strong dissociation between subjective perception of time and timing of physical events.

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