Figure 1.

Behavioral Tasks. (A) The Probabilistic Reward Task (PRT). For each trial, a cartoon face stimulus was presented, after which a mouth (or a nose, depending on task version) appeared briefly (100 ms) on the face and the participant was instructed to indicate (via buttom press) whether the mouth (or nose) was long or short. After the participant responded (or 2500 ms elapsed) feedback was presented. Correct responses for one (“rich”) stimulus were rewarded 3 times more frequently than correct responses for the other (“lean”) stimulus. The asymmetrical reward schedule induced a response bias in which participants were more likely to respond accurately to the “rich” stimulus than the “lean” stimulus. (B) Participants either completed a 2-block (100 trials/block) or a 3-block (100 trials/block) version of the task (task version was entered as a covariate in the analyses). Displayed is average response bias for each block of trials, for the subgroup of participants who completed each version of the task. (C) For analyses, to enable collapsing across task versions, participants’ change in response bias from the first (block 1) to the last (either block 2 or block 3) was computed, and z-scored within the subgroup of participants who completed each version of the task. Z-scored response bias was then collapsed across task versions; however, task version was a covariate in analyses. Displayed is the distributions of z-scored response bias across all participants.