The differentiation of rhythmic structure.

Listeners judged whether two five-tone nonmetric rhythms were the same or different. Each rhythm was presented one, two, or four times to study the process of perceptual differentiation. The results indicated that the listeners perceived these rhythms in terms of the grouping of the tones, and not in terms of the timing between the groups. Two rhythms that had the same perceptual grouping were judged as being identical, even if the timing between the groups was different. The perception of the groupings of tones developed gradually. If each rhythm was presented only once, then the listeners had only a global percept, focused on groups (runs) of three elements, and often judged two different rhythms as being identical. If the rhythms were presented two or four times, then the grouping of the tones became more differentiated and the listeners were less likely to judge different patterns as being identical. Thus, perception of auditory rhythmic structure appears to follow the same developmental process as the perception of visual spatial structure.