Reinforcement of a behavioral standard modifies individual differences under alcohol.

OBJECTIVE: Whether alcohol increases or decreases individual differences relative to sober levels may depend on the situation in which behavior is measured. This study tested the hypothesis that reinforcement and behavioral standards will modify the effects of alcohol on individual differences.
METHOD: Two groups of male social drinkers (N = 12) performed a psychomotor task under repeated doses of alcohol (0.62 g/kg), and received verbal feedback (FB) for matching an easy or a difficult performance standard.
RESULTS: FB reduced between-subject and within-subject differences under alcohol, especially when coupled with the easy standard. Between-subject and within-subject differences were equivalent under alcohol and sober conditions when variance introduced by changing blood drug concentrations was controlled. The consistency of an individual's performance across doses depended on the consistency of his criterion response.
CONCLUSIONS: Situational factors alter individual differences under alcohol, and pharmacological intoxication alone does not appear to account for undue variability in behavior under moderate doses.