Interpersonal conflict increases interpersonal neural synchronization in romantic couples.

Previous studies on dual-brain social interaction have shown different patterns of interpersonal neural synchronization (INS) between conflictual and supportive interactions, but the role of emotion in the dual-brain mechanisms of such interactions is not well understood. Furthermore, little is known about how the dual-brain mechanisms are affected by relationship type (e.g., romantic relationship vs. friendship) and interaction mode (e.g., verbal vs. nonverbal). To elaborate on these issues, this study used functional near-infrared spectroscopy to collect hemodynamic signals from romantic couples and cross-sex friends while they were discussing conflictual, neutral, or supportive topics. For the couples but not the friends, INS between the sensorimotor cortex of both participants was greater when discussing the conflictual topic than when discussing the supportive topic. INS was positively correlated with the arousal level but not the valence level of communication contents. INS was also positively correlated with interpersonal physiological synchronization based on galvanic skin response, a physiological measure of arousal. Furthermore, the differences in INS between the conflictual and supportive topics were closely associated with verbal rather than nonverbal behaviors. Together, these findings suggest that it is the arousal level induced by verbal interactions during interpersonal conflicts that increases romantic couples' INS.