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Abstract:
Why does chanting, drumming or dancing together make people feel united? Here we investigate the neural mechanisms
underlying interpersonal synchrony and its subsequent effects on prosocial behavior among synchronized individuals. We
hypothesized that areas of the brain associated with the processing of reward would be active when individuals experience
synchrony during drumming, and that these reward signals would increase prosocial behavior toward this synchronous
drum partner. 18 female non-musicians were scanned with functional magnetic resonance imaging while they drummed a
rhythm, in alternating blocks, with two different experimenters: one drumming in-synchrony and the other out-ofsynchrony
relative to the participant. In the last scanning part, which served as the experimental manipulation for the
following prosocial behavioral test, one of the experimenters drummed with one half of the participants in-synchrony and
with the other out-of-synchrony. After scanning, this experimenter ‘‘accidentally’’ dropped eight pencils, and the number of
pencils collected by the participants was used as a measure of prosocial commitment. Results revealed that participants
who mastered the novel rhythm easily before scanning showed increased activity in the caudate during synchronous
drumming. The same area also responded to monetary reward in a localizer task with the same participants. The activity in
the caudate during experiencing synchronous drumming also predicted the number of pencils the participants later
collected to help the synchronous experimenter of the manipulation run. In addition, participants collected more pencils to
help the experimenter when she had drummed in-synchrony than out-of-synchrony during the manipulation run. By
showing an overlap in activated areas during synchronized drumming and monetary reward, our findings suggest that
interpersonal synchrony is related to the brain’s reward system.
