Pilot study
A pilot study (N=13 social drinkers) found surprising results (Figure 3). In this pilot study, participants discriminated normal trials (e.g., with black elements) from differently coloured oddballs (e.g., with green elements). Participants completed the task twice, in separate sessions on separate days (a standard procedure in alcohol research, see Halsall et al. 2021 for meta-analysis). In one session they drank 0.65g/kg alcohol before EEG recording, in the other they drank an equivalent placebo drink before EEG recording. Despite our pre-registered predictions (https://aspredicted.org/xp4dd.pdf), alcohol enhanced the SPN, particularly during later 400-1000 ms time window (t (12) = -4.188, p < .001, dz = 1.161). This suggests alcohol may disinhibit the visual cortex, making it more sensitive to task-irrelevant symmetry. However, this unexpected result required replication. The pilot study also found that alcohol had no effect on the P1 peak (t (12) = -0.112, p = .913, dz = 0.031), and reduced N1 dip (t (12) = 4.460, p < .001, dz = 1.237).