Interfering with activity in the dorsomedial prefrontal cortex via TMS affects social impressions updating

Chiara Ferrari, Tomaso Vecchi, Alexander Todorov, Zaira Cattaneo

In our everyday social interactions we often need to deal with others' unpredictable behaviors. Integrating unexpected information in a consistent representation of another agent is a cognitively demanding process. Several neuroimaging studies point to the medial prefrontal cortex (mPFC) as a critical structure in mediating social evaluations. Our aim here was to shed light on the possible causal role of the mPFC in the dynamic process of forming and updating social impressions about others. We addressed this issue by suppressing activity in the mPFC by means of 1 Hz offline transcranial magnetic stimulation (TMS) prior to a task requiring participants to evaluate other agents' trustworthiness after reading about their social behavior. In two different experiments, we found that inhibiting activity in the mPFC increased perceived trustworthiness when inconsistent information about one agent's behavior was provided. In turn, when only negative or positive behaviors of a person were described, TMS over the mPFC did not affect judgments. Our results indicate that the mPFC is causally involved in mediating social impressions updating-at least in cases in which judgment is uncertain due to conflicting information to be processed.