Antagonism shapes social maps in the human brain.

Human relationships form a complex web of affiliative and antagonistic ties. Yet how the brain represents their affective structures remains unclear. Here, using a television drama depicting intertwined friendships and rivalries, we examined how the brain encodes the valence of interpersonal relationships. Participants underwent fMRI scanning before and after watching the drama while viewing the faces of its central characters. They then rated each character pair for relationship strength and valence, and whole-brain representational similarity analysis (RSA) identified brain regions representing these relational structures. Relationship valence effects were most prominent for antagonistic (negative) relationships in the left anterior supramarginal gyrus and right medial prefrontal cortex. Univariate analyses revealed increased activation in the precuneus after drama viewing, suggesting enhanced retrieval of narrative-related person knowledge, though this region did not show statistically significant representational similarity patterns reflecting interpersonal relationships. These findings indicate that the human brain constructs a multidimensional social map from narrative experience, with antagonistic ties playing important role in shaping social relationship representations.