To test the hypothesis that alcohol impairs posterror behavioral adjustment (Ridderinkhof et al., 2002), we calculated behavioral interference effects [RT on incongruent trials (e.g., black-tool) minus RT on congruent trials (e.g., black-gun)] and compared their magnitude on trials that followed correct responses to trials that followed errors using a 3 (Beverage group) × 2 (Trial type: posterror, postcorrect) mixed factorial ANOVA. A significant Beverage group × Trial type interaction, F(2, 64) = 3.16, p < .05 (see Figure 5), showed that RT interference effects were smaller on trials after errors compared to trials after correct responses for participants in the placebo group, t(21) = 2.38, p = .02, consistent with previous findings (Ridderinkhof et al., 2002) and with the general notion of posterror adjustment (e.g., Rabbitt, 1966). Control group participants showed a similar pattern, but the means did not differ reliably (t < 1). No such differences were apparent for participants in the alcohol group, however, t(22) = −1.33, p = .25. Additional contrasts showed that, whereas postcorrect interference effects were unaffected by beverage group (F < 1), posterror interference
