Visual enhancement of auditory beat perception across auditory interference levels.

This study dealt with audiovisual rhythm perception involving an observed movement. Two experiments investigated whether a visual beat conveyed by a bouncing human point-light figure facilitated beat perception of concurrent auditory rhythms, and whether this enhancement followed a profile of multisensory integration. In Experiment 1, participants listened to three repetitions of a metrically simple rhythm and detected a perturbation in the third repetition. The rhythm was presented alone or with a visual beat in phase to it. Both conditions were presented with or without an auditory interference sequence at four increasing tempi, which served to progressively weaken the beat of the auditory rhythm. In Experiment 2, participants tapped to a regular auditory beat in the same combinations of visual beat and auditory interference. Results showed that the visual beat improved the perception of (Experiment 1) and the synchronization to (Experiment 2) the auditory rhythms. Moreover, in both experiments, visual enhancement was greater when the performance in the unisensory (auditory) conditions was poorer, consistent with the principle of inverse effectiveness. The relative multisensory gain increased as auditory performance deteriorated, except in one intermediate level. Together these results demonstrate that rhythmic visual movement aids auditory rhythm perception, which may be subserved by a perceptually integrated audiovisual beat that couples the internal motor system.