On the precision of timing during joint rushing

When individuals synchronize their movements during joint actions, they systematically accelerate the prescribed tempo: the so-called joint rushing phenomenon. While research has focused on the resulting drift in accuracy, it remains unexplored whether interpersonal synchronization also affects precision of timing. Pooling together 110 participants from three inde- pendent finger-tapping experiments, this study addresses this gap by analyzing the Weber fraction, the standard deviation of the tapping errors relative to interval duration, by comparing Solo and Joint synchronization in sub-second durations. The results revealed that joint synchronization causes a dramatic, duration-scaled degradation of accuracy (rushing), yet imposes only a small, roughly duration-independent cost on precision, whose non-linear profile across durations was overall preserved in both conditions. This pattern suggests that interpersonal synchronization largely affects period correction while overall preserving phase correction, a distinction relevant to current theoretical models of temporal coordination in social behavior.