Procedure
Participants attended the EEG laboratory on the University campus between 12:00 and 19:00. They first provided a breath alcohol reading to ensure they had consumed no alcohol prior to the study. Participants then completed a study checklist to make sure they were aware of the conditions of participation and that they have had a meal beforehand. After the pre-screening, participants were fitted with the EEG cap.
Participants were then presented with 3 glasses containing a drink and were instructed to spend 12 minutes consuming the drink and approximately 3 minutes per glass. They completed a subjective effects scale (SES, Morean et al., 2013) before they consumed any drink, in the middle of drink consumption, and after all drinks were consumed.
After drink consumption, the EEG experiment began with 24-trial practice block. Participants then completed the experimental task which lasted approximately 20 minutes. Finally, they completed another SES after the experiment was finished. Breathalyser readings were taken at the beginning of each session, 10 minutes post drink consumption, and after experimental task completion.
The EEG experiment involved 260 trials. These were broken into 10 blocks of 26. Within each block, there were 10 symmetry normal trials (e.g., black or green symmetry), 10 random normal trials (e.g., black or green random), 3 symmetry oddball trials (e.g., green or black symmetry), and 3 random oddball trials (e.g., green or black random). The trials were presented in a randomized order. Each trial began with a 1.5 second baseline period, followed by a 1.5 second pattern presentation. Participants in the Oddball task judged whether the patterns were green or black. Judgments were entered in a non-speeded fashion after stimulus offset using the left (A) and right (L) keys on a standard keyboard. The response mapping varied unpredictably between trials. On half the trials the A key was used to report one option (e.g., Green, as in Figure 4) and the L key was used to report the other option (e.g., Black, as in Figure 4). The Regularity task was identical to the Oddball task, except that participants judged whether the stimuli were Regular or Random.