Figure 1.

Sequence of stimulus events within a trial of the reinforcement learning and choice task. A, Following selection of one of the two stimuli, the choice was visualized to the subject by a white frame (presented for 300 ms) around the corresponding symbol. This was immediately followed by positive or negative feedback, according to the task schedule. B, In the subsequent choice phase, symbols were rearranged to yield 12 novel combinations of symbols. In addition, the three pairs from the learning phase were also presented. Trials were identical to those from the learning phase, with the exception that no outcome was presented. Of particular interest in this phase were so-called win–win trials (highlighted in blue) and lose–lose trials (highlighted in red) in which two symbols associated with a very high or very low probability of reinforcement, respectively, were combined.