Complexity matching in side-by-side walking

•Interpersonal coordination is a very common phenomenon in daily-life activities.•We present the alternative frameworks which have been proposed for accounting for such situations.•We propose statistical tests, for distinguishing between these theoretical hypotheses.•We applied these tests on series collected during synchronized walking.•The results are consistent with the complexity matching hypothesis.

Interpersonal coordination represents a very common phenomenon in daily-life activities. Three theoretical frameworks have been proposed to account for synchronization processes in such situations: the information processing approach, the coordination dynamics perspective, and the complexity matching effect. On the basis of a theoretical analysis of these frameworks, we propose three statistical tests that could allow to distinguish between these theoretical hypotheses: the first one is based on multifractal analyses, the second and the third ones on cross-correlation analyses. We applied these tests on series collected in an experiment where participants were instructed to walk in synchrony. We contrasted three conditions: independent walking, side-by-side walking, and arm-in-arm walking. The results are consistent with the complexity matching hypothesis.