Frequentist analysis
P1 peak and N1 drop effects were analysed with separate mixed ANOVAs. These had two within subjects’ factors [Regularity (symmetry, random) X Block (alcohol, placebo)], and one between subject’s factor [Task (Oddball, Regularity)]. The SPN was first computed as a difference between symmetry and random in two separate time windows. This was analysed with mixed ANOVA [Interval (early, late) X Block (alcohol, placebo)], and one between subject’s factor [Task (Oddball, Regularity)]. The presence of an SPN in all windows was confirmed with one sample t tests (symmetry – random < 0).