The participants completed two independent sessions of a word association
learning task, adapted from a previous study of feedback processing
in the striatum (Tricomi and Fiez, 2008; illustrated in Fig. 1).
During this feedback-based learning task, the participants learned arbitrary
word pairs through trial and error. Each trial required the participants
to associate one main word with one of two other word choices,
as in a multiple choice test with two response options. Since the
words were semantically unrelated, learning was entirely dependent
on the feedback that followed each response.