Proceedings of the Annual Meeting of the Cognitive Science Society

In group rhythmic behavior, the tempo increase phenomenon can emerge even when participants appear well synchronized. We analyzed collective clapping from 49 participants while manipulating modality (auditory/visual/audiovisual) and group size (pair/trio). We tested a sequential effect in which beat-wise asynchrony A(k) predicts the subsequent tempo change _(k). For each trial, we estimated accel and plateau phases by fitting a one-breakpoint piecewise linear regression to the smoothed tempo series and selecting the breakpoint kp via an AIC-based grid search, using only the tempo series to avoid circular inference. In the confirmatory analysis w=7, an AR(1) mixed-effects model revealed a robust sequential effect: larger asynchrony predicted a more negative immediate tempo change (shorter subsequent ICI). The coupling was stronger during accel and attenuated toward zero during plateau, and it was strongest in the visual condition during accel. An exploratory check across w=1...15 yielded consistent patterns.