No abstract

Wing and Kristofferson (1973) have shown that temporal precision in self-paced tapping is limited by variability in a central timekeeper and by variability arising in the peripheral motor system. Here we test an extension of the Wing-Kristofferson model to synchronization with periodic external events that was proposed by Vorberg and Wing (1994). In addition to the timekeeper and motor components, a linear phase correction mechanism is assumed which is triggered by the last or the last two synchronization errors. The model is tested in an experiment that contrasts synchronized and self-paced trapping, with response periods ranging from 200-640 ms. The variances of timekeeper and motor delays and the error correction parameters were estimated from the auto-covariance functions of the inter-response intervals in continuation and the asynchronies in synchronization. Plausible estimates for all parameters were obtained when equal motor variance was assumed for synchronization and continuation. Timekeeper variance increased with metronome period, but more steeply during continuation than during synchronization, suggesting that internal timekeeping processes are stabilized by periodic external signals. First-order error correction became more important as the metronome period increased, whereas the contribution of second-order error correction decreased. It is concluded that the extended two-level model accounts well for both synchronization and continuation performance.

No abstract

Most studies of synchronization have focused on how an established phase relationship between selfproduced events (e.g., ®nger 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 selfpaced ®nger taps. In Exp. 1, the metronome period was constant and equal to the mean of the self-paced interresponse intervals, whereas the initial phase dierence 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 dierence 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 dierent task variables and contribute dierently to sensorimotor synchronization.

In a study of perceptual synchronization with an isochronic sequence, subjects were given the following task: They heard an isochronic sequence of tones in which the last interval was either correct or too long. Their task was to detect irregularity. The independent variables were the number of tones heard and the time interval between them. The dependent variable was the difference limen (DL) for the detectability of the irregularity. Two experiments were performed in this study, differing in the way in which the trials were blocked: In Experiment 1, stimuli with the same period were presented in blocks, whereas in Experiment 2, the period of the stimulus was randomized. The results show that in Experiment 1 the number of tones in the stimulus did not affect the detectability of the anisochrony. In Experiment 2, the number of the DL was a decreasing function of the number of tones heard. Moreover, the decrease of the DL was larger than one would expect from a simple model of information integration, which assumes that subjects improve their performance by averaging their percepts of the first intervals in the sequence. The difference between this task and experiments on the discrimination of temporal intervals is discussed.The ability of human subjects to synchronize their internal timekeepers with external temporal patterns of different complexity has been a topic of experimental and theoretical investigations for a long time (see Fraisse, 1982, for a comprehensive summary of the literature). One motivation for the present study was to imitate in a laboratory task the temporal aspect of the performance of musicians or of listeners to music. How precise is a subject when he/she taps in synchrony with a metronome? Are there any systematic errors in the timing? How well can subjects apprehend more complicated temporal patterns and reproduce them?These matters have essentially been investigated with two different tasks. In tapping tasks, the subject has to tap in synchrony with a temporal pattern or to continue tapping after the pattern stops. In perceptual tasks, the subject has to make judgments about temporal aspects of the temporal patterns or adjust them to meet certain perceptual criteria. Obviously, in tapping tasks an explicit sensory-motor coordination has to be achieved. The perceptual task mayor may not include an implicit motor activity (e.g., tapping with the feet during the perceptual task). Although there have been many perceptual studies in which subjects have discriminated two temporal intervals or judged single intervals (Allan & Kristofferson, 1974), perceptual experiments with several isochronic sequences have been rare. At least two perceptual experiments with several isochronic sequences have been performed. Lunny (1974) constructed a metronome in which every fourth click could be adjusted. Using the method of limits, he (as his own subject) adjusted the temporal position of this click until an irregularity was just detectable. He found an approximate Weber law in the range of 30 to 1,000 mse...