Self-regulators - A hidden dimension of interaction: Movement similarity and temporal proximity increase the perception of interpersonal coordination in third party observers

•Self-regulatory movements and their perception are of direct interest to the theory of the cooperative signalling characteristic of language.•Movement similarity and temporal proximity are the most perceptually salient characteristics of self-regulators.•The perceptual biases towards mimicry and synchrony could have evolved for interpersonal coordination.

In everyday circumstances, humans use a variety of cues to draw rich inferences about the nature of interaction. Among these, we focus on sequences of self-regulatory movements, such as touching behaviours and postural changes, that have long been related to interpersonal coordination understood both in terms of mimicry and synchrony. So far, there has been a severe lack of studies on the third party perception of interactional phenomena, including self-regulators. Here, we investigate which elements of the interactional dynamics induce the perception of interactants' behaviours (represented by self-regulators) as causally related, and show that the most important factor responsible for such attribution is the similarity of observed movements. On a more general plane, we hope to make a step towards uncovering perceptual biases that evolved for interpersonal coordination, thus shedding some light on the human interactional potential and its evolution.