Prior to completing 10 blocks of 80 experimental trials, participants completed 7 blocks of 28 practice trials, during which performance was monitored by the computer program to ensure that each participant attained a speed/accuracy balance that produced approximately 10% errors. Participants making fewer errors were instructed to respond more quickly. No feedback was given during the experimental trials. Given that ERN amplitude decreases as the number of errors increases (see Gehring et al., 1993; but see Olvet & Hajcak, 2009), this comparability in performance ensured that any decrease in ERN amplitude in the alcohol group was not due simply to a larger number of errors in that group relative to the other groups. In addition, and similar to previous studies in which response confidence judgments have been recorded (Bartholow et al., 2012; Scheffers & Coles, 2000), following the response on each trial a 3-point scale appeared on the screen, with anchor points labeled “Sure Correct”, “Don’t Know”, and “Sure Incorrect.” Participants were instructed to indicate their confidence in the correctness of the response they just made by pressing one of
