Musical Meter Induces Interbrain Synchronization during Interpersonal Coordination

Behavioral performance on the coordination task between the meter and no-meter conditions in experiment 1. A, Mean interpersonal time lag (Mean lag). Shorter mean interpersonal time lag in the meter condition compared with that in the no-meter condition. B, Hurst exponent H of the detrended fluctuation analysis. There was no significant difference in H between the meter and the no-meter conditions. C, The linear regression of interpersonal time lags across taps in the meter and no-meter conditions. The interpersonal time lags significantly decreased across taps in the meter condition. Colored lines indicate behavioral measures for each dyad. Black lines indicate the averaged values across dyads. Error bars represent SEMs.

Interbrain synchronization (IBS) during the coordination task. The heat maps of the IBS in (A) experiment 1 and (D) experiment 2. Enhanced IBS was observed at channel 6 in the range of frequencies of 0.026–0.030 Hz in the meter condition compared with the no-meter condition. In experiment 2, the IBS in channels 5 and 10 (frequencies: 0.060–0.065 Hz) was greater in case of strong meters than weak meters. The distributions of the cluster statistic of the permutated data in (B) experiment 1 and (E) experiment 2. The black dashed lines indicate the positions of the cluster statistic of the pairs. The enhanced IBS in (C) experiment 1 and (F) experiment 2. Data were plotted through boxplots, in which the horizontal lines indicate median values, the boxes indicate the 25% and 75% quartiles, and the error bars represent the minimum/maximum values. The diamond dots represent the extreme values.

Correlation between interbrain synchronization (IBS) and behavioral coordination in experiment 1. The IBS at channel 6 during the coordination task was negatively associated with the mean interpersonal time lag in the meter condition. Each black point depicts a dyad of the mean interpersonal time lag of the participants (y-coordinate) and IBS at channel 6 (x-coordinate). The solid line represents the least-squares fit. The shaded area indicates the 95% confidence interval.

Behavioral coordination in experiment 2. A shorter mean interpersonal time lag (Mean lag) was observed in strong meters relative to weak meters. Boxplots are presented, with the horizontal lines indicating the median values, boxes indicating the 25% and 75% quartiles, and error bars representing the minimum/maximum values. The diamond dots represent the extreme values; *p < 0.05.