Beyond syncopation: The number of rhythmic layers shapes the pleasurable urge to move to music.

People experience the strongest pleasurable urge to move to music (PLUMM) with rhythms of medium complexity, showing an inverted U-shaped relationship. Rhythmic complexity is typically defined by syncopation but likely interacts with the number and instrumentation of rhythmic layers (e.g., snare only vs snare and bass drum) in affecting PLUMM. This study investigated this interaction by comparing PLUMM ratings of rhythms with varying rhythmic layers and syncopation degrees. Two online studies (study 1, n = 108; study 2, n = 46) were conducted asking participants to rate how much they wanted to move and the pleasure they felt while listening to rhythms. Each study used 12 rhythms in four versions: 1) snare only (SN) in study I and bass drum only (BD) in study II; 2) snare and hi-hat (SN + HH) in study I and bass drum and hi-hat (BD + HH) in study II; 3) snare and bass drum (SN + BD) and 4) the original with snare, bass drum, and hi-hat (SN + BD + HH) in both studies, totaling 48 stimuli per study. We tested for linear and quadratic effects of syncopation and rhythmic layers on PLUMM ratings. Study I showed a significant interaction between syncopation and rhythmic layers. The SN + BD + HH versions exhibited the strongest inverted U as an effect of syncopation, followed by SN + BD and SN + HH, while SN showed a near-flat pattern of ratings as an effect of syncopation. Study II had similar findings, but differences between versions were smaller, and the interaction was mainly driven by differences between BD and BD + HH and between SN + BD and SN + BD + HH, especially at moderate syncopation levels. These findings suggest that the PLUMM response is shaped by the number of rhythmic layers, the roles that the different instruments play, and the way that they interact with each other and with syncopation, thus extending our understanding of the rhythmic features that drive the motor and hedonic responses to music.