Paper short abstract:

Synchronised action, such as in music and dance, often results in a social bonding effect. This may arise from the brain's drive to reduce uncertainty, as synchronised movement is a highly predictable social interaction, and the same principle may be applied to social coordination across timescales.

Paper long abstract:

Research both in the field and in the lab has observed a social bonding effect arising from synchronised action. It has been suggested that synchronised movement may engage the same reward systems associated with social grooming in other primates, allowing humans to utilise synchrony as a more efficient behaviour for bonding. The precise mechanism through which synchrony engages our reward systems is poorly understood, but one theory is that we find synchrony rewarding because it is more predictable and thus easier than non-synchronised social interactions. This draws upon a general principle that the brain is a predictive engine, aiming to reduce uncertainty in the environment. Synchronised action - being typified by repetitive, periodic movements in the other that can be predicted from those performed by the self - is then highly rewarding.

This theory may be extended across multiple timescales. In the case of musical performance, a common example of synchrony across cultures, people may synchronise their movements and breathing at the rhythmic level. In addition, they may harmonise their voices, which mechanically involves synchronisation of vibrations in the vocal folds, which is perceived as musical pitch. Finally, they may synchronise their behaviour at the scale of days and weeks, by coming together to sing at regular intervals in a doctrinal ritual mode. In this way, ritualised and synchronised actions may serve to increase predictability within a social group, creating social bonds through the rewards generated by prediction fulfilment, while a lack of multiscale synchrony may be socially disruptive.