The Brain Basis Of Prosocial Effects Of Interpersonal Synchrony

In real life,people are always instructed to perform some actions at the same time.If they show movement concordance at temporal or spatial dimension,there will be a kind of interpersonal synchrony.Previous studies have shown that interpersonal synchrony fosters the prosociality to each other,such as helpfulness;we call it as prosocial effects of interpersonal synchrony.However,the underlying brain basis of such effects is not clear.Different from traditional brain research(focusing on single brain activity),recent brain imaging studies have shown that interactive behavior(i.e.,interpersonal synchrony)is associated with the coherence between two brains,named inter-brain synchronization.The present study proposes that the brain basis of prosocial effects of interpersonal synchrony is inter-brain synchronization from the perspective of social interaction.Then,it is supposed that self-other merging,referred to unable to distinguish self-and other-information,plays an important role in prosocial effects of interpersonal synchrony,how does such factor play a role in such effect? Further,if the self-related information is highlighted,such as priming self awareness(the inner subjective state of individual when he is aware of himself),does this affect inter-brain synchronization?The present study aims to explore the brain basis underlying the prosocial behavior in the context of interpersonal synchrony and its influence factors.Functional nearinfrared spectroscopy(fNIRS)and hyperscanning technique were used to simultaneously measuring the brain activities of the interacting participants.Swing arms/ pressing keys at the same time was selected as the task for interpersonal synchrony.To measure the prosociality,on the one hand,participants were asked to decide the portion of sharing punishment to help the interactive partner;on the other hand,they had to report the time they would like to help the partner who was assumed in trouble.The self-other merging was measured through a morphing face distinguish task.To prime self awareness,participant were instructed to find the first-person pronoun “I” when they were reading the experimental stimulus.The results showed that:(i)whatever the passive movement synchrony or the active movement synchrony,the inter-brain synchronization during movement synchrony was positively correlated with subsequent mutual prosociality,including helping behavior and inclination(Experiment 1,2).(ii)Self-other merging mediated the relationship between the inter-brain synchronization during movement synchrony and mutual helping behavior(Experiment 3),but the mediation effect was not significant when putting self-other similarity or positive emotion as the mediating factors(Experiment 4).(iii)After priming self awareness,the helping behavior reduced,the self-other merging decreased,the inter-brain synchronization during movement synchrony diminished,and the mediation of self-other merging disappeared(Experiment 5).Our results indicated that the inter-brain synchronization predicted subsequent mutual prosociality;more important,such prediction was mediated by self-other merging,suggesting the possible mechanism of prosocial effects of interpersonal synchrony;further,self awareness modulates the inter-brain synchronization during movement synchrony and prosocial effects of interpersonal synchrony.This study revealed the relationship between inter-brain synchronization and prosocial effects of interpersonal synchrony,and examining the mediation of self-other merging,the modulation of self awareness on the effect.The current work will enrich our understanding for the formation and development of prosocial behavior,and provide inspirations for maintaining and fostering prosocial behavior in our daily life.