A Kuramoto model of self-other integration across interpersonal synchronization strategies

Human social behaviour is complex, and the biological and neural mechanisms underpinning it remain debated. A particularly interesting social phenomenon is our ability and tendency to fall into synchronization with other humans. Our ability to coordinate actions and goals relies on the ability to distinguish between and integrate self and other, which when impaired can lead to devastating consequences. Interpersonal synchronization has been a widely used framework for studying action coordination and self-other integration, showing that even in simple interactions, such as joint finger tapping, complex interpersonal dynamics emerge. Here we propose a computational model of self-other integration via within- and between-person action-perception links, implemented as a simple Kuramoto model with four oscillators. The model abstracts each member of a dyad as a unit consisting of two connected oscillators, representing intrinsic processes of perception and action. By fitting this model to data from two separate experiments we show that interpersonal synchronization strategies rely on the relationship between within- and between-unit coupling. Specifically, mutual adaptation exhibits a higher between-unit coupling than within-unit coupling; leading-following requires that the follower unit has a low within-unit coupling; and leading-leading occurs when two units jointly exhibit a low between-unit coupling. These findings are consistent with the theory of interpersonal synchronization emerging through self-other integration mediated by processes of action-perception coupling. Hence, our results show that chaotic human behaviour occurring on a millisecond scale may be modelled using coupled oscillators.Author summary: Interacting with other people is crucial for our everyday life. We regularly and without much effort synchronize our movements with other people’s movements, across a wide range of interactions such as when dancing together and performing music. However, even a very simple interaction such as tapping a rhythm together can result in complex interaction dynamics. Two people tapping can choose different synchronization strategies, such as leading-following wherein one person is a leader and the other a follower, mutual adaptation where both adapt to each other, or leading-leading where both try to lead at the same time. In this paper we show how these strategies can be described using a mathematical model of coupled oscillators. Specifically, we show how the strategies rely on different coupling strengths between the oscillators in the model. This shows that even complex human behaviour may be modelled using simple mathematical terms.