Simultaneous Beat Tracking of Two Auditory Rhythmic Periodicities

Abstract

Polyrhythms are central to many musical practices. However, the extent to which people can simultaneously track multiple non-metrically related beat patterns remains unclear. Here we studied people's ability to simultaneously track multiple periodic streams containing beat patterns that cannot be perceived according to a single metric framework. Participants listened to one or two beat patterns simultaneously in three conditions: single stream, selectively attending to one of the streams, and simultaneously attending to both streams. Using a probe-tone paradigm, we assessed whether they were tracking the pattern's periodicity, while recording their brain activity using EEG. The EEG showed limited effects of attention. However, our behavioral results show that, while performance during dual attending is overall worse than selective attending and single stream listening, people are able to perform the dual attending task above chance levels, indicating that they can at least extract and evaluate temporal information from both periodic streams simultaneously. We also found evidence of one group being better at dual attending than another. Our findings suggest that tracking of polymetric streams is possible, and that this ability may depend on individual difference.