Two competing types of theory have been proposed about the function of dorsal anterior cingulate cortex (dACC): evaluative theories hold that dACC monitors ongoing behavior to detect errors or conflict, whereas response selection theories hold that dACC is directly involved in the decision making process. In particular, one response selection theory proposes that dACC utilizes reward prediction error signals carried by the midbrain dopamine system to decide which of several competing motor control systems should be given control over the motor system (Holroyd and Coles, 2002). The theory further proposes that the impact of these dopamine signals on dACC determines the amplitude of a component of the event-related brain potential called the error-related negativity (ERN). In the present study, we applied this theory to a decision making problem that requires participants to select between two response options in which an erroneous choice is not clearly defined. Rather, the reward received for a particular response evolves in relation to the individual's previous behavior. We adapted a computational model associated with the theory to simulate human performance and the ERN in the task, and tested the predictions of the model against empirical ERP data. Our results indicate that ERN amplitude reflects the subjective value attributed by each participant to their response options as derived from their recent reward history. This finding is consistent with the position that dACC integrates the recent history of reinforcements to guide voluntary choice behavior, as opposed to evaluating behaviors per se.