Stimulus-reinforcement association learning and reversal learning are assessed by means of a simple computerized card game with play money stakes. Participants are shown two decks, one, mostly a winning deck (win: 6 times out of 7) and the other, mostly a losing deck (lose 6 times out of 7). The subject must choose a deck at each trial and feedback regarding win or loss is provided after each choice. After the learning criterion of eight consecutive cards chosen from the winning pack is met, the contingencies are switched. This constitutes the reversal phase of the task. If the criterion is again met, the contingencies are switched again for a total of 50 trials, allowing up to 50 reversals. Points are gained for each correct response and lost for each incorrect response. The ability to “unlearn” the association between a stimulus and reward and re-associate the stimulus with punishment is a distinct, frontally mediated, form of learning as shown in both animal (Ongur & Price, 2000) and imaging studies (O’Doherty et al., 2001; Rogers, Andrews, Grasby, Brooks, & Robbins, 2000). This
