The subject’s references in synchronization and pseudo-synchronization.

Abstract

ABSTRACT-This experiment compared subjects' behavior when they synchronized their taps with an auditory sequence and when they continued to tap while controlling the sounds with the taps, so that the sounds appeared to be perfectly synchronized with the taps (pseudo-synchronization). In pseudo-synchronization, subjects' behavior was quite different depending on whether or not they had been informed about the experimental method. Informed subjects produced almost constant intervals, on average. Uninformed subjects accelerated, believing that they were tracking a sound sequence. This result highlights that in the synchronization of taps with sounds, the tap always anticipates the sound. More fine-grained analyses revealed that asynchronies and memory for preceding intervals both play a role in anticipation, their relative contribution depending on the rate of the sequence.' Translated from the French* by Bruno H. Repp REFERENCES IN SYNCHRONIZATION When synchronizing a series of taps with an isochronous sequence of sounds, the subject benefits from two series of references: (a) the constant intervals [between sound onsets]3 and (b) the coincidence of (or the asynchronies between) taps and sounds. If the subject relies only on the first index, the period of the taps will be equal to that of the sounds, but the two series can be misaligned in time. There is synchronization, but only in terms of a matching of periods; the subject does not care about the asynchronies between taps and sounds. If subjects rely on the tap-sound coincidence, they seek to minimize the asynchronies. This is then synchronization in terms of coincidence of the events of the two series and, in addition, there is a matching of periods. The latter is no longer [based on] a reference but rather is a consequence [of the phase alignment of the two series]. One might think that subjects use both kinds of references, to varying extents. In practice, we know that the dominant phenomenon is undoubtedly the search for tap-sound coincidence, because it is very difficult to produce a series of taps that is syncopated - i.e., shifted relative to the stimulus series - [when the sequence tempo is fast] (Fraisse & Ehrlich, 1955). However, the tap-sound coincidence is only relative. The variability of the asynchronies is not negligible and, moreover, a systematic error reflecting a slight anticipation of the sound by the tap is quite often observed. Moreover, the synchronization task has sometimes been considered as a task of pursuit. In a test designed to measure the precision of synchronization with repeated rhythmic patterns, R. H. Seashore found that the results were best predicted by a multiple correlation with the results of C. E. Seashore's test of rhythmic ability and a test of visual-motor pursuit (r= .74).4 SYNCHRONIZATION AND PSEUDO-SYNCHRONIZATION In order to study more precisely the role of the indices used by subjects, we have thought of a situation in which subjects, after a period of normal synchronization, would be deprived of the references furnished by possible asynchronies. To achieve this, we suppressed the asynchronies using a setup in which it is the tap that produces the sound. In that case, tap and sound are perfectly simultaneous. The actual procedure of the experiment was as follows: Subjects were instructed to synchronize their taps (on a telegraph key) as closely as possible with an isochronous series of sounds. At the beginning of each series, the sounds were produced by a timer that controlled discharges of the condenser in a loudspeaker. Starting at time T, shortly after the 20th sound heard, the discharge of the condenser was no longer controlled by the timer but by the subject's own taps, with the subject not having been informed of this technical trick. We will call this phase pseudo-synchronization. Sounds and taps were recorded on [kymograph] paper moving at a speed of 10 cm/s. …