 We will measure brain activity using functional magnetic resonance imaging fMRI, in conjunction with the performance of reinforcement processing tasks from the literature. These paradigms involve either the passive observation of reinforcement contingencies, or the requirement to make an appropriate response within a time window in order to earn positive feedback. The ongoing study uses two specific paradigms: one examining the impact of brain responses to feedback on subsequent learning, and one investigating how brain responses to a monetary reinforcer are modulated by the unexpectedness of the event. 