Why do we fall into sync with others? Interpersonal synchronization and the brain’s optimization principle

Abstract

Spontaneous interpersonal synchronization of rhythmic behavior such as gait or hand clapping is a ubiquitous phenomenon in human interactions, and is potentially important for social relationships and action understanding. Although several authors have suggested a role of the mirror neuron system in interpersonal coupling, the underlying brain mechanisms are not well understood. Here we argue that more general theories of neural computations, namely predictive coding and the Free Energy Principle, could explain interpersonal coordination dynamics. Each brain minimizes coding costs by reducing the mismatch between the representations of observed and own motor behavior. Continuous mutual prediction and alignment result in an overall minimization of free energy, thus forming a stable attractor state.

Musical interaction is influenced by underlying predictive models and musical expertise

“…wherein an action-perception loop is created such that one person's action output becomes another's perceptual input, and vice-versa 4,19,43 . However, explicit synchronization as encountered in our study may be a more complex phenomenon.…”

“…Viewed from the framework of predictive coding under the free energy principle, the brain constantly attempts to optimize its use of energy by minimizing the error between its predictions and the sensory input 45 . Thus, when humans are interacting, spontaneous synchronization may occur as a result of individuals minimizing the differences in self/other representations 19 . In our study, the decreased SI seen at the start of the non-shared RCM trials may represent the participants individually searching for a magnitude of variability wherein they are able to minimize the difference between self and other representation.…”

“…what another's intention to act is, when they will act temporally, and where in the common space they will act 15 . Joint action may thus best be understood within a predictive coding framework 6,[16][17][18][19] .…”

“…Hence, we were able to quantify the effects of the internal predictive model on synchronization within the dyads. Previous research has emphasized the necessity of shared predictive models of successful interactions, and we therefore hypothesized that a non-shared RCM would result in decreased synchronization measures 19 . We expected this effect to occur due to discrepancy between the perceived stimuli and the internal predictive model.…”

“…Further, based on earlier studies, we hypothesized that a leading-following strategy would be more prominent in the non-shared RCM condition 2,4 (for an overview of synchronization strategies, see Figure 3). While the underlying mechanisms of synchronization strategies remains a topic of discussion, recent research suggests that mutual adaptation is the most efficient strategy and is premediated by a merging of self-other representation 19 . In joint finger tapping tasks, this would entail considering the auditory feedback created by the other as linked to one's own action.…”