Perception of Rhythmic Similarity is Asymmetrical, and Is Influenced by Musical Training, Expressive Performance, and Musical Context

Rhythm is an essential part of the structure, behaviour, and aesthetics of music. However, the cognitive processing that underlies the perception of musical rhythm is not fully understood. In this study, we tested whether rhythm perception is influenced by three factors: musical training, the presence of expressive performance cues in human-performed music, and the broader musical context. We compared musicians and nonmusicians’ similarity ratings for pairs of rhythms taken from Steve Reich’s Clapping Music. The rhythms were heard both in isolation and in musical context and both with and without expressive performance cues. The results revealed that rhythm perception is influenced by the experimental conditions: rhythms heard in musical context were rated as less similar than those heard in isolation; musicians’ ratings were unaffected by expressive performance, but nonmusicians rated expressively performed rhythms as less similar than those with exact timing; and expressively-performed rhythms were rated as less similar compared to rhythms with exact timing when heard in isolation but not when heard in musical context. The results also showed asymmetrical perception: the order in which two rhythms were heard influenced their perceived similarity. Analyses suggest that this asymmetry was driven by the internal coherence of rhythms, as measured by normalized Pairwise Variability Index (nPVI). As predicted, rhythms were perceived as less similar when the first rhythm in a pair had greater coherence (lower nPVI) than the second rhythm, compared to when the rhythms were heard in the opposite order.