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Abstract:
Prolonged exposure to asynchronous audiovisual stimulus pairs changes the perception of audiovisual simultaneity. It has been proposed that this change occurs by adjusting the perceptual latency of stimuli in order to minimize perceived audiovisual asynchrony. How is this adjustment achieved? For signals with a gradual onset, perceptual latency can be minimized by decreasing detection threshold (or vice-versa). Here we assess whether this occurs following recalibration of simultaneity. Participants were exposed for 5 minutes to asynchronous (150ms) audiovisual stimulus pairs with either light or sound leading. Auditory stimuli were presented via headphones, visual via an LED. Detection thresholds for visual and auditory stimuli were then measured with a 2IFC task interleaved with short re-exposures to the asynchrony. Results indicate that while the detection threshold for visual stimuli does not significantly vary, the detection threshold for auditory stimuli critically depends on which modality leads during
asynchronous audiovisual exposure. All nine participants tested were more sensitive in detecting auditory stimuli after light-leading exposure than after sound-leading. We suggest that by becoming more or less sensitive to sound the brain is able to change the perceptual latency of auditory stimuli to minimize audiovisual asynchrony, while keeping the perceptual latency of visual stimuli relatively constant.
