Frustration reduces interpersonal competition through dynamic interpersonal neural synchronization in dyads.

Frustration reduces competitive willingness in social interactions, yet the underlying dynamic neural mechanisms remain unclear. Using functional near-infrared spectroscopy (fNIRS) hyperscanning, we record dyadic hemodynamic activity during a competitive task following a frustration task. Results show that frustration progressively reduces competitive willingness. Accordingly, increased interpersonal neural synchronization (INS) is observed in the frontopolar cortex (FPC) during the middle stage and the dorsolateral prefrontal cortex (dlPFC) during the late stage. FPC INS mediates the effect of frustration on competition performance. Role differences are determined based on frustration task performance, and Granger causality analysis reveals a bidirectional influence that is significantly stronger from leaders to followers. These findings suggest that frustration enhances cognitive control and executive function in the middle stage through increased INS in FPC, and enhances inference of others' intentions in the late stage through increased INS in dlPFC, thereby dynamically reducing competition. This study reveals a distinct neural pattern of interpersonal competition processes under frustration.