The error-related negativity (ERN) is a response-locked brain potential generated when individuals make mistakes during simple decision-making tasks. In the present study, we examined ERN under conditions of reward and punishment, among participants who scored extremely low or high on the socialization scale of the California Psychological Inventory (CPI). Participants completed a forced-choice task, and were rewarded for correct responses in half the trials, and punished for incorrect responses in the remaining trials. A significant interaction between socialization (SO) and condition revealed that low-SO participants produced smaller ERNs during the punishment task than during the reward task, whereas high-SO participants produced similar ERNs in both conditions. Reaction time and electromyogram data essentially bolster the interpretation that the ERN effects reflect differences in error salience for high-SO and low-SO participants, and are consistent with the avoidance-learning deficits seen in psychopathy.