Gender-specific interpersonal neural synchronization during same-gender closeness-building interactions among strangers: an fNIRS hyperscanning study

Background Self-disclosure, sharing of personal information, is crucial for initiating and deepening interpersonal relationships. Although it has been consistently shown that mutual self-disclosure fosters closeness between strangers, the underlying dual brain neural mechanism remains unexplored. This study aims to uncover these gender-modulated differences and their underlying neural mechanisms. Method We investigated the interpersonal neural synchronization (INS) among zero-history, same-gender strangers. We applied the functional near-infrared spectroscopy (fNIRS) hyperscanning technique to simultaneously measure the brain hemodynamic activities of 32 female and 30 male dyads. Participants engaged in an adapted Fast Friends paradigm, featuring a naturalistic interaction progression from superficial "small talk" to incrementally escalating levels of mutual self-disclosure. Results The structured interactions elicited significant increases in self-disclosure, emotional arousal, and perceived interpersonal closeness as the tasks progressed from the no-disclosure stage to increasingly intimate self-disclosure stages. This psychological escalation was accompanied by significantly enhanced INS between the dorsolateral prefrontal cortex (DLPFC) and temporoparietal junction (TPJ) exclusively during the deep self-disclosure stage relative to the no-disclosure stage. Crucially, gender significantly moderated the relationship between this cross-regional coupling and relationship-building outcomes (closeness: β = -0.386, p_FDR = .025). For female-female dyads, INS significantly mediated the relationship between self-disclosure and closeness (indirect effect = 0.03); however, these associative and mediation pathways were entirely absent in male-male dyads. Conclusion These findings illuminate the dual-brain neural underpinnings of relationship initiation, highlighting that relationship formation between females may rely more heavily on emotional verbal expression and INS than their male peers. This advances theoretical models of social cognition and offers insights into developing strategies for various social settings.