Impulsivity, a personality characteristic of many psychiatric disorders including substance abuse, involves a preference for immediate rewards over delayed rewards and a disregard of long-term consequences. This application hypothesizes that dysregulation of the ventral tegmental (VTA) dopaminergic reward prediction system leads to a reward hypersensitivity in orbitofrontal cortex (OFC) systems of stimulus evaluation and anterior cingulate cortex (ACC) systems of behavior monitoring among highly impulsive subjects. The proposed experiments investigate reward sensitivity in stimulus evaluation and action monitoring utilizing the temporal resolution of ERPs and spatial resolution of fMRI. The experiments employ normal college students screened and separated into high and low impulsive groups, based on the Barrett Impulsivity Scale, participating in a modified flanker task with rewarding and punishing stimuli testing for reduced ACC activation to errors in impulsive subjects, in a passive S1/S2 paradigm testing for enhanced OFC activation to the prediction of reward in impulsive subjects, and an SI/S2 incentive flanker paradigm examining interactions between OFC and ACC in a reward-motivated decision task.