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. Significance StatementUnderstanding how humans form mental representations of others is fundamental to the study of social behavior. Yet we know little about how these representations evolve as people get to know each other over time. Using brain imaging in a real-world social network of first-year high school students, we tracked how participants neural representations of their classmates changed over the course of a year. While some brain regions encoded stable, shared representations of peers, others showed increasingly individualized patterns. These findings shed light on how real-world social experiences shape representations of familiar others and delineate how the brain balances both personal experience and shared social information. This work informs theories of social cognition by showing how mental representations evolve over time.