Interpersonal Trust In The Economic Exchange Game

Interpersonal trust,defined as “a psychological state comprising the intention to accept vulnerability in virtue of positive expectations of the intention or behavior of another”,is essential to prime,establish and maintain social relationships.Previous studies have demonstrated that interpersonal trust has cognitive,affective and intentional components.Some studies have speculated the correlations of interpersonal brain activities while interpersonal trust is emerging.However,how does interpersonal trust dynamically change and what’s the potential neural basis underlying interpersonal trust are still unclear.In our studies,two persons’ brain activities during interaction were recorded simultaneously by the functional near infrared spectroscopy(fNIRS)based hyperscanning technique.Firstly,how individuals build interpersonal trust in economic exchanges? In Experiment 1,participants of 27 dyads were recruited to play 10 rounds of trust game,in which one invested to the other(investor to trustee,Investment Phase),the other repaid it(trustee to investor,Repayment Phase)and they achieved income themselves(Total Income Phase).As the investor and the trustee increase money-given from early rounds(1-5)to late rounds(6-10)they showed the increased right-temporo-parietal interpersonal brain synchronization(IBS),which was more enhanced in viewing the total income compared with viewing the outcomes of investment or repayment.The dyad-wise IBS increase was influenced by the investment increase(late rounds minus early rounds)and such an influence was fully mediated by the corresponding repayment changes.Experiment 1 suggested that interpersonal trust emerged in the interaction between the investor and the trustee,and revealed the potential neural basis underlying interpersonal trust(Inter-Brain Synchronization).Secondly,how is the interpersonal trust affected by the social context factors(e.g.,social hierarchy,socioeconomic status)of economic exchange game? In Experiment 2,researchers manipulated the social context factor of social status(participant groups involve 17-paired difference-in-status group and 19-paired non-difference-in-status group).In the non-difference-in-status group,interpersonal trust and the corresponding IBS haven’t been observed.However,in the difference-in-status group,money-given increase between the investor and the trustee still emerged from early rounds to late rounds,accompanied by the increased right-temporo-parietal interpersonal brain synchronization(IBS)as well.The IBS increase could be predicted by the investment increase and the corresponding repayment changes.Experiment 2 indicates that the establishment of interpersonal trust and its neural activities would be affected by the social context factor.Integrating the results from two experiments,it was found that inter-brain synchronization occurred in right TPJ during the establishment of interpersonal trust,and the synchronization was correlated with trust behaviors of investor and trustee.Moreover,when trustee encountered with the investor with higher status,their inter-brain synchronization correlating with their trust behaviors will enhance.Meanwhile,the investor who was in high status dominated their relationship in the economic exchange game.These findings tend to support motivation attribution hypothesis which interpreted the dynamic change of interpersonal trust.