Getting to Know You: Neural Representations of Other People Grow More Perceiver-Specific Over Time

Mental representations of others are central to social behavior, yet little is known about how these representations evolve over significant periods of time as people get to know one another. In this longitudinal functional magnetic resonance imaging study, we tracked how neural representations of familiar peers changed over the course of a school year among two cohorts of first-year high school students (N = 150) embedded in newly formed social networks. We assessed the extent to which individuals' neural representations of their classmates converged with group-level norms - capturing the balance between information that is idiosyncratic to each perceiver and that which is shared across perceivers - and how this changed over time. We identified brain regions where neural representations of familiar peers were well aligned across perceivers, including several areas implicated in person perception, social cognition, and visual processing. Across both cohorts of participants, neural representations in the hippocampus and lateral prefrontal cortex began as highly aligned across participants, then grew more idiosyncratic to each perceiver over time. Similar effects were observed in the ventral medial prefrontal cortex, but only in one cohort of participants. Regions often linked to social cognition (temporoparietal junction, superior temporal sulcus) evinced strong encoding for group normative information at both timepoints. Taken together, these findings suggest that neural representations of familiar others may initially be predominantly driven by information that is consistent across perceivers (e.g., physical appearance, face-based evaluations, and trait impressions), then become more unique over time as each perceiver gains their own experiences with and impressions of these individuals.