Figure 4A shows the initial response to alcohol or placebo. For the first 5 subjective measures shown, the initial response to alcohol was an increase while for tiredness, a decrease was observed. About half of the subjects rated anxiety zero at all time points, and of the remainder, roughly equal numbers of subjects reported increases as reported decreases. During the placebo infusion, mean responses were in a similar direction as those observed during the alcohol infusion, but were much smaller. The perceived number of drinks dropped by approximately 1. Figure 4B shows the adaptive response. All 7 subjective measures showed acute tolerance to alcohol infusion (i.e., negative values, indicating a return toward baseline), regardless of the direction of the initial response. For the placebo infusion, the direction of the adaptive response indicated acute tolerance for all measures except tiredness, which showed acute sensitization; again, much smaller subjective responses were reported during placebo infusions.
