We investigated the relationship between action-outcome contingency and stimulus-preceding negativity (SPN), a motivationally sensitive event-related potential. Neuroimaging studies have shown that insular cortex (a known source of the SPN) is more activated prior to rewards that are contingent on prior correct action than rewards that are given gratuitously. We compared two gambling tasks, one in which the participant attempted to guess the profitable key-press option (choice) and one in which rewards were simply given at random (no-choice). The SPN that developed in anticipation of feedback was larger in the choice condition, especially at right anterolateral sites. These findings suggest that the SPN specifically reflects the expectation of response reinforcement, rather than anticipatory attention toward emotionally salient stimuli.