Synchrony perception of audiovisual speech is a reliable, yet individual construct.

Audiovisual (AV) (a)synchrony perception, measured by a simultaneity judgment task, provides a proxy measure for the temporal binding window (TBW), the interval of time within which participants perceive individual auditory and visual events as synchronous. The TBW is a sensitive measure showing group level differences across the lifespan. However, the significance of these findings hinges on whether AV synchrony perception is characteristic to an individual and whether it is reliable across sessions. As there is little evidence to this latter assumption, this work aimed to establish test-retest reliability of the TBW. Eighteen participants completed a simultaneity judgment task, twice, on different days, where they judged whether or not the audio and video of word-length speech stimuli were presented at the same or different times. Results showed effects of task familiarity indicated by significantly faster response times observed at the second timepoint. The slope and amplitude asymptote of the TBW also increased, however no change in TBW suggests no change in sensitivity to AV (a)synchrony. The combination of high within-subject correlations (R = 0.71) and substantial intersubject variability provide strong support for the TBW as a robust measure of AV temporal perception, and suggest a conserved mechanistic underpinning within individuals.