Social coordination dynamics: measuring human bonding

Abstract

Spontaneous social coordination has been extensively described in natural settings but so far no controlled methodological approaches have been employed that systematically advance investigations into the possible self-organized nature of bond formation and dissolution between humans. We hypothesized that, under certain contexts, spontaneous synchrony-a well-described phenomenon in biological and physical settings-could emerge spontaneously between humans as a result of information exchange. Here, a new way to quantify interpersonal interactions in real time is proposed. In a simple experimental paradigm, pairs of participants facing each other were required to actively produce actions, while provided (or not) with the vision of similar actions being performed by someone else. New indices of interpersonal coordination, inspired by the theoretical framework of coordination dynamics (based on relative phase and frequency overlap between movements of individuals forming a pair) were developed and used. Results revealed that spontaneous phase synchrony (i.e., unintentional in-phase coordinated behavior) between two people emerges as soon as they exchange visual information, even if they are not explicitly instructed to coordinate with each other. Using the same tools, we also quantified the degree to which the behavior of each individual remained influenced by the social encounter even after information exchange had been removed, apparently a kind of social memory.

Keywords: Coupling; Emergence; Entrainment; Interpersonal; Social memory; Spontaneous Synchronization; Vision.

Figure 1. Experimental set-up and design

(A) Participants sat in front of each other and were instructed to look at each other’s finger when they executed the task with their eyes open. (B) Note that the experimental set-up allows participants to see the movements of their own finger as well as the movements of the other person sitting in front of them. (C) Detail of the experimental procedure in the O-C-O (Open-Closed-Open) and the C-O-C (Closed-Open-Closed) conditions.

Figure 2. Relative phase between the participants’ movements

(A–D) Displacement of the index finger of both participants during representative trials in the (A) closed-open-closed C-O-C and (B) open-closed-open O-C-O conditions. (C–D) Peak-to-peak relative phase φ between the movements of the index finger of the participants during C-O-C (C) and O-C-O (D). (E–F) Distribution of all the relative phase φ-values in 20° bins across all pairs of participants (n=6) and all trials (10 per pair) during C-O-C (E) and O-C-O (F). The yellow overlays outline spontaneous synchronization.

Figure 3. Frequency overlap between the participants’ movements

(A–B) Representative trials for the C-O-C (A, same trial as Figures 1A and C) and the O-C-O conditions (B, same trial as Figures 1B and D). Each individual plot represents a 20s segment. Power spectra of the movements of each participant are plotted as well as the frequency overlap. (C–D) Mean and standard deviation of the power spectrum overlap, PSO, across all pairs of participants (n=6) and all trials (10 per pair) for the Closed-Open-Closed C-O-C (C) and the Open-Closed-Open O-C-O (D) conditions. The yellow overlays outline spontaneous synchronization.

Figure 4. Directionality effect in peak frequency changes in the C-O-C condition

Power spectrum of the movement of the participant with (A) the lowest (L) initial preferred frequency (red) and (B) the highest (H) initial preferred frequency (blue) for each of the three time segments. For both participants, the effects of opening and closing the eyes is illustrated by green and black arrows respectively. (C–D) Grand average of the peak frequencies for each kind of participant (L & H) in each time segment. T-test significance: * p < .05, ** p < .01.