On the limits of anisochrony in pulse attribution

Pulse is the subjective experience of isochrony, which is typically elicited by series of sensory events with close to isochronous spacing, as is common in music and poetry. We measured the amount of anisochrony in a 10-event sequence with 570- to 630-ms nominal inter-onset intervals (IOI) that corresponded to the threshold for pulse attribution. This threshold was 8.6% of the IOI across 28 participants with a wide range of musical training, as compared with 3.5% for detection of anisochrony in the same kind of sequence. Musical training led to lower thresholds for detection of irregularity but had no effect on pulse attribution. The relatively larger amount of anisochrony in pulse attribution may reflect the limit for predicting and synchronising with future events. We suggest that this limit reflects a compromise between tolerance for naturally occurring deviations and the need for precision in timing.