Anticipation of rhythmic stimuli: Speed of establishment and precision of synchronization (1966).

Abstract

3 In a series of experiments, we [found the following]4: (a) Establishment of synchronization of taps with sounds presented as a sequence or as a rhythm, when the subject must start tapping with the first sound, is very rapid. From the third stimulus (or the third cycle in the case of a simple [repeated] rhythm) onward, simultaneity is achieved with [an error of less than] 50 ms. Reorganization after a perturbation or a change in rhythm is also rapid. (b) The precision of synchronization as a function of sequence tempo ([intervals] between successive sounds ranging from 375 to 6000 ms) is excellent up to 1500 ms. Beyond [that tempo], there is no longer any real synchronization of taps and sounds. On the other hand, if synchronization is established by responding with a tap to each sound, as in a series of reaction times (RTs), the timing of the responses varies little as a function of tempo. This form of synchronization is very difficult to carry out with rapid sequences, [at rates] below 1/s. (c) The process of anticipation is analogous to that found in pursuit tasks; [reactions to inserted stimuli] show that the preparation for action organizes itself progressively during the whole period intervening between two stimuli.Translated1 from the French by Bruno H. Repp2Synchronization of our gestures with repetitive stimuli is such a commonplace phenomenon that it no longer sufficiently astonishes us. One-year old infants rock to the rhythm of music and, by the time they are three or four years old, are capable of accompanying the beats of a metronome with taps (Fraisse, Pichot, & Clairouin, 1949). Armies parade easily by stepping in time to the rhythm of music.In each case, synchronization is possible in such a way that the motor command anticipates the arrival of the sound and [thus] makes possible the simultaneity of the response and the stimulus. Under what conditions is this motor command established, and with what precision does it function? Our studies will address these two questions.Study 1: Establishment and Reestablishment of SynchronizationI. How Is Synchronization Established?Two situations can present themselves. [In one,] we hear either a sequence or a rhythm before executing a movement.5 In that case, it seems we can produce synchronous movements right away. This is the case of a troop [of soldiers] starting out to the rhythm invited the subject to start tapping in a synchronous manner when he felt ready.7 Before that of a march. The anticipation exists from the outset. But what is its precision?The second case is one in which the subject must attempt to track the sounds from the beginning of their production.6 In that case, the subject's first tap can only be a reaction to the stimulus, but what happens subsequently? How does the subject arrive at synchronization of stimuli and taps?To investigate this problem, we chose two [stimulus] conditions:(a) An auditory sequence with intervals of 800 ms between [the onsets of] successive sounds.(b) A rhythmic structure of 200 -600 ms [that is, having alter- nating interonset intervals of 200 and 600 ms].The sounds were produced by a frequency generator. The subject's task was to synchronize taps on a Morse key (moving 1 mm) with the sounds. Sounds and taps were registered on a Sefram paper-roll recorder at a speed of 10 cm/s, which enabled us to measure the simultaneity of sound and tap with a precision of 0.5 mm, or 5 ms.We used three tasks:(A) The subject positioned the hand flat [on the table] in front of the Morse key. The experimenter activated the sequence and invited the subject to start tapping in a synchronous manner when he felt ready.7 Before that moment, he had to inhibit all movement of hand and foot, and even speech. Actually, subjects began to tap rather quickly-that is, after five or six sounds.(B) The subject also had the hand positioned flat in front of the Morse key. …