Warmth is more influential than competence

Previous neuroimaging studies have revealed neural representation of traits in the medial prefrontal cortex (mPFC), but related studies mainly investigated the neural representation of warmth or competence trait respectively. To identify the potential differences of trait codes of warmth and competence in the mPFC, we applied functional magnetic resonance imaging (fMRI) repetition suppression which is a rapid reduction of neuronal responses upon repeated presentation of the same implied trait. Participants read two successive trait-implying behavioral descriptions. In each trial, the critical target sentence implied either a warmth-related or competence-related trait was preceded by a prime sentence that implied trait from the other dimension of the 'Big Two' with a same or opposite valence, or no trait. The results revealed robust repetition suppression from prime to target in the mPFC only when the prime was a warmth-related trait, regardless of valence. Critically, the suppression effect was much stronger after being primed with a similar and opposite warmth trait compared with a trait-irrelevant prime. This suppression pattern was found nowhere else in the brain. The result seems to indicate that humans do not completely interpret and represent warmth and competence traits as independent dimensions and the warmth trait is more influential than Competence trait. The finding extends the understanding of the 'Big Two' theory of impression formation from the aspect of neural activity.