Investigations of the Mechanisms Underlying Audio-Visual Temporal Recalibration

Our perception of synchrony is malleable. With prolonged exposure to audio-visual asynchrony (adaptation), we are more likely to perceive synchrony when stimuli are slightly offset (in the adapted order) than if those stimuli are physically synchronous. For example, after only minutes of watching a film with a persistent audio-lag, we are more likely to perceive synchrony when audio is slightly lagging vision than when these stimuli are physically synchronous. This shift in synchrony perception is known as temporal recalibration (TR). The mechanisms underlying audio-visual TR are contended. Some suggest that TR results from changes in sensory coding, while others suggest TR results from shifts in decision-level synchrony criteria. This thesis aimed to determine which of three candidate mechanisms is most likely to underlie audio-visual TR. Two experiments investigated two major distinctions in the predictions of currently proposed mechanisms: the impact of task requirements on TR and the symmetry of TR (i.e., whether the adapted and unadapted order are recalibrated together or perceived independently). The combination of predictions regarding TR symmetry and task requirements allowed competitive comparison of the validity of these mechanisms. Experiment 1 replicated typical effects of TR, demonstrating the efficacy of the current adaptation and testing protocols. Experiment 2 demonstrated that adaptation yields asymmetrical TR, and that task requirements impact TR. These findings suggest changes in decision-level synchrony criteria drive TR, challenging purely sensory mechanisms. This project therefore concluded that decision-level processes likely underlie TR. Suggestions are made for future research to further assess the accuracy of this conclusion