Fig. 1.

The probabilistic reversal-learning task. An example of several consecutive trials in the probabilistic reversal-learning task is shown (running from bottom totop). On each trial, subjects are presented with two abstract visual patterns. Using trial-and-error feedback, subjects must discover which of the two patterns is correct (here indicated by asmall arrowhead on top of the pattern to improve legibility). Feedback (a green smiley face or red sad face) is presented as soon as the subject has chosen one of the patterns by a left or right button press.