On this task, participants are asked to learn which of two patterns is more likely to be associated with reward. On each trial, participants are presented with two abstract visual patterns simultaneously. Participants are instructed to guess which pattern is most likely to be associated with reward. They are given feedback (correct or incorrect) after each choice. Participants were told, however, that no stimulus was rewarded all the time, and furthermore, that the "rewarded" stimulus changed occasionally. Participants were then told that once they decided which stimulus was most likely to be rewarded, they should stay with that choice until they felt that the stimulus most likely to be rewarded had changed. Participants made choices abut three different sets of abstract visual patterns. For each pattern, the task started with an intial learning acquisition phase, where one of the stimuli was reinforced 80% of the time (a choice of the other stimulus was reinforced the remaining 20% of the time). Once participants reached a criterion of 9 choices of the more-frequently reinforced stimulus in a block of ten trials (in 50 or fewer total trials), the reinforcement contingencies for the stimuli were reversed: the stimulus that was reinforced 80% of the time previously was now reinforced only 10% of the time and the other was reinforced 90% of the time. The probabilities changed from the initial acquisition phase to the "reversal" phase in order to make the task difficulty of the two types of phases more similar. To reach criterion in the reversal phase, participants need to choose the new stimulus that is most likely to be rewarded 9/10 times in a block of trials (within a total of 50 trials). If participants are able to reach criterion in this phase, the reinforcement contingencies are reversed one more time (staying at 90%/10%), and participants need to learn to choose the stimulus that was originally most likely to be rewarded, in order to reach criterion. Thus, each participant completes up to 2 reversal stages with each stimulus pair (or up to 6 total, along with the 3 initial discrimination stages).