red or green to signify either a win or a loss (with red or green as the winning color counterbalanced across participants), and the unchosen box turned the other color (either green or red) to indicate what the outcome of the trial would have been had that box been chosen. The feedback stimulus appeared for 1000 ms, followed by a blank screen for 1500 ms preceding the onset of the next trial. Replicating the design used by Gehring and Willoughby (2002), all four possible combinations of 5 and 25 (i.e., 5-5, 5-25, 25-5, and 25-25) were evenly crossed with the four possible win/loss outcomes (win-win, win-loss, loss-win, loss-loss), resulting in 16 trial types; thus, while the participant’s choice produced a designated outcome on each trial, signaled by the feedback, outcomes on future trials were not predictable from outcomes associated with prior choices (analogous to a roulette wheel or slot machine). Two sets of these 16 trial types, ordered randomly, were included in each block. Upon completion of a block, participants received feedback about their win/loss ratio within that block. Participants completed 12 blocks of 32 trials.
