Distinct neural routes for evaluative and informational social influence

Humans routinely revise their judgments based on input from others, but the brain mechanisms that distinguish evaluative from informational social influence remain unclear. We combined a preregistered electroencephalography (EEG) experiment (N = 87) with the Judge-Advisor System to identify how two common forms of social information - feedback and advice - shape judgment and decision-making. Participants made numerical estimates, received either feedback (good/bad) or advice (a specific alternative estimate) that was either close to or far from their own, and then revised their response. Across behavioral and neural indices, both information types showed proximity-dependent effects, yet diverged in their temporal dynamics. Feedback elicited a feedback-related negativity (FRN) that decreased with confidence, indicating reflexive performance monitoring. Advice produced sustained late positive complex (LPC) activity whose onset slowed with higher confidence and lower proximity, reflecting deliberate integration of external information. For both, P300 amplitudes increased with proximity, consistent with the reward value of social validation. These findings reveal two complementary neurocognitive routes by which social information guides decisions: a rapid evaluative route engaged by feedback and a slower deliberative route engaged by advice. The results identify distinct temporal signatures of how the human brain incorporates others' input to refine its own judgments.