Abstract:  Human societies are unique in terms of large-scale social cooperation and trust between unrelated people (generalized trust). As an important social signaling mechanism, generalized trust reduces transaction costs, facilitates cooperative behavior, and promotes human society’s prosperity. The question of why and when people trust each other has important implications for human social interaction and economic decision-making. Previous fMRI research utilizing the Trust Game has revealed brain regions involved in the decision to trust, including medial prefrontal cortex, caudate nucleus, amygdala, insula and dorsolateral prefrontal cortex. However, the extant research has failed to clearly reveal neurophysiological mechanisms of the investor’s decision-making in the Trust Game. To investigate the time course and neural oscillation courses of trust decision-making, we recorded the electroencephalographic (EEG) data of 21 healthy human participants while they played the role of trustor in the one-shot Trust Game; in this game, participants made decisions to trust or distrust the counterpart. In addition to behavioral data analysis and event-related potential (ERP) analysis, we also conducted spectral analysis to examine the neural oscillations underlying the trust game responses. Behavioral results indicated that participants made trusting decisions more than chance. Electrophysiological results suggested that distrusting choices induced a more negative N2 and a less positive P3 than did trusting choices. Spectral analysis results showed that the beta-band (18~28 Hz, 250~350 ms) power for distrusting choices was significantly larger than trusting choices; this may suggest greater inhibitory control exerted to distrust. Moreover, trusting choice after a negative outcome elicited a significant higher beta-band (15~20 Hz, 150~300 ms) power than did trusting choice after a positive outcome, while the beta-band power for distrusting choice after a negative outcome was similar compared to distrusting choice after a positive outcome. Our study provided some new insights into the psychophysiological processes underlying human’s decisions to trust strangers. Specifically, when making a decision to trust or distrust the counterpart, the distrusting choice induced a larger N2 than did the trusting choice, which may reflect greater cognitive control to inhibit trusting behavior. On the other hand, a more positive going P3 for the trusting choice than the distrusting choice may suggest that increased attention and motivation are associated with the trusting behavior. Moreover, the increased beta power across frontal areas for distrusting choices might reflect frontal inhibitory processes. These findings highlight the ingrained norm of cooperation and trust in modern societies, and provide preliminary spatio-temporal and spectral results understanding human’s decision-making in the one-shot Trust Game.

Key words: generalized trust, decision-making, N2, P3, Time-frequency analysis