Although response confidence ratings were not directly relevant to the current hypotheses, making these ratings introduced a delay between trials, raising the possibility that group differences in post-error and post-correct indices of control could arise from differences in the accuracy or the time taken to make the ratings. Across groups, participants were equally able to classify the accuracy of their responses (Control: M = .95, SD = .04; Placebo: M = .95, SD = .05; Alcohol: M = .96, SD = .02; F[2, 90] = .20, p = .82). However, the control group made these ratings more quickly (M = 2673 ms, SD = 369) than either the placebo (M = 2905 ms, SD = 293; F[1, 57] = 7.25, p = .01) or alcohol groups (M = 3029 ms, SD = 294; F[1, 57] = 17.06, p < .001), whose confidence rating RTs did not differ reliably, F(1, 62) = 2.87, p = .10. RT was included as a covariate in the ERP analyses, and was not significant, nor did its inclusion alter any effects of interest.1 Therefore, we do not consider this issue further.
