The generation of two isochronous sequences in parallel

Subjects were presented with two parallel pulse trains through earphones, one to each ear. The pulse trains were isochronous, and the durations of the intervals associated with the right and left trains were systematically varied, so as to give rise to both simple rhythms and polyrhythms. The subjects were required to tap with the right hand in synchrony with the train delivered to the right ear, and to tap with the left hand in synchrony with the train delivered to the left ear. Accuracy of performance in polyrhythm contexts was substantially lower than in simple rhythm contexts, and decreased with an increase in the complexity of the associated polyrhythm. It was concluded that the performer develops a representation of the pattern as an integrated whole, and that performance accuracy is inversely related to pattern complexity.