Person knowledge is independently encoded by allocentric and egocentric reference frames within separate brain systems

Humans spontaneously infer information about others to perceive the similarity in behaviors and traits among people in our social environments. However, evaluating the similarity among people can be achieved through multiple frames of reference: other-to-other differences (allocentric similarity) or self-to-other differences (egocentric similarity), which are difficult to dissociate with behavioral measures alone. Here, we use functional magnetic resonance imaging to test whether the similarity of brain response patterns when thinking of others and the self is predicted by models of allocentric and egocentric similarity in the trait-judgments of well-acquainted peers from 20 independent groups of people (total N = 108; within-subject design). Results show that both allocentric and egocentric similarity during person representation are reflected in brain response similarity patterns when thinking of others but do so differentially and in non-overlapping brain systems. Specifically, allocentric similarity was positively related to brain similarity patterns in distributed regions involved in social cognition as well as in regions involved in general non-social spatial reference frame encoding. Egocentric similarity was inversely related to brain response similarity but only within dorsal regions of the medial prefrontal cortex and anterior cingulate, suggesting that activation within this region is important for dissociating selfrepresentation from that of similar others. These results suggest that the brain processes both kinds of reference frames independently to encode trait information about conspecifics that we use to represent person knowledge about other people within realworld social networks.