Synchronization in joint action: from tapping to fire-walking

Synchronization of actions, goals, and intentions among people is an important phenomenon in successful social interactions, which has been studied in both intentional and unintentional scenarios. It has been observed in coordination tasks requiring mutual information exchange between individuals, as well as scenarios of unidirectional coupling whereby one individual aligns with another through mimicking or simulation. In order to explore the dynamics and mechanisms involved in entrainment, a finger tapping experiment was carried out. Pairs of subjects were asked to tap on their respective keyboards following an 8-beat stimulus. They were instructed to keep the given beat as precisely as possible as well as synchronize with the ‘other’, while they received auditory feedback of themselves tapping, the other, or the computer metronome. Analysis of their inter-tap intervals showed that dyads were unable to achieve full synchrony but rather in the attempt to lock in phase with each other, they corrected their tapping onsets in opposite directions. Windowed cross-correlations revealed high correlation in both lag +1 and -1 in the interactive condition, suggesting a shared continuous adaptation to the other’s output. Unintentional synchronization was also considered through a second study, looking at heart rates of spectators and participants during a fire-walking ritual. Preliminary analysis revealed high synchronization among family members. Dynamical systems analysis showed that both types of interactions may be represented through varying degrees of coupling strengths between people, possibly correlated with their affinity to one another; however, even through indirect contact with each other, people do not adopt leader/follower positions.