Brain-to-brain synchrony during shared reminiscing predicts connection and memory in romantic couples

Romantic partners often revisit relationship-defining memories together, reconstructing a shared account of their relationship through conversation. Such shared reminiscing can strengthen interpersonal connection by fostering alignment in thoughts, feelings, and perspectives, an experience known as shared reality. Here, we used functional near-infrared spectroscopy to record brain activity simultaneously from romantic couples during naturalistic, face-to-face conversations. Couples first discussed an unresolved conflict and then jointly recounted their relationship origin story, including how they first met and how their relationship developed. Shared reality decreased following the conflict discussion and returned to baseline levels after the origin story. While recounting their origin story, partners exhibited synchronized activity in the right medial frontopolar cortex, a region implicated in autobiographical memory and reasoning about close others. This synchrony was not observed at rest or during the conflict discussion. Greater medial frontopolar synchrony between partners during the origin story discussion was associated with higher post-conversation shared reality, closeness, and relationship satisfaction, even after accounting for baseline relationship quality. It also predicted better subsequent memory for the conversation, an association that was robust to controlling for the importance and familiarity of the memories being discussed. Together, these findings reveal how the interbrain alignment that emerges during shared reminiscing tracks both the connection partners experience and what they later remember. Our work bridges relationship science and social neuroscience through the naturalistic neuroimaging of live social interaction, and offers a window into the neural processes that accompany mutual understanding, social connection, and sharing memories in romantic relationships.