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How consensus-building conversation changes our minds and aligns our brains

How do people come to share a way of seeing the world? We show that consensus-building conversation can align future brain activity. We scanned participants' brains as they watched previously unseen movie clips with ambiguous narrative content. Participants then gathered in conversation groups with the goal of coming to a consensus about each movie clip’s narrative. Finally, participants were scanned while viewing the clips again, along with novel clips from the same movies. We found that group members' neural activity became more aligned after conversation, with each group achieving a distinctive pattern of alignment reflecting their unique discussion. This alignment persisted over novel clips, framing new but related information. Finally, we found that participants who were central in their real-world social networks played an outsized role in creating group alignment, both by facilitating conversation and by being more likely to adapt their own brain activity to the group. These results suggest that the effects of conversation on private thought are a powerful determinant of social influence. We discuss implications for theories of social influence, language, and the mind.