Figure 1.

Number reduction task (NRT) illustrated by an example trial. Subjects sequentially transform a given sequence of the three digits (1, 4, and 9) into a new sequence to determine the final result of this trial (Response 7 [R7] – Fin). The hidden task structure implemented in all trials is that the digits used as last three responses mirror the previous three responses (illustrated by the pairwise arrows at the bottom of the figure), which implies that the second response is always equal to the final result (R2 = R7).