Getting synchronized with the metronome: Comparisons between phase and period correction

Most studies of synchronization have focused on how an established phase relationship between self-produced events (e.g., finger taps) and the clicks of a metronome is maintained when the metronome is regular or subject to unpredictable perturbations. Here we study how synchronization is initially established, using an experimental paradigm in which the metronome is activated after the subject has executed a series of self-paced finger taps. In Exp. 1, the metronome period was constant and equal to the mean of the self-paced inter-response intervals, whereas the initial phase difference of the metronome from the taps varied across trials. The synchronization error patterns could be predicted by a linear phase correction model. Experiment 2 involved both period and phase correction. The initial phase difference was constant, whereas the metronome period varied across trials. The observed synchronization error patterns suggest that the subjects achieved synchronization either by reacting to the second metronome signal or by aiming at the third metronome signal. The pattern of the residual synchronization errors was consistent with the linear phase correction model. These results support the notion that period and phase correction mechanisms are called for by different task variables and contribute differently to sensorimotor synchronization. Received: 20 November 1996 / Accepted: 20 April 1997