Expectancy and pharmacological effects of alcohol on human cognitive and motor performance: the compensation for alcohol effect.

The expectancy versus pharmacological effects of alcohol have been primarily studied in relation to social and affective behaviors. The present study extended this type of investigation to perceptual, cognitive, and motor behaviors and utilized two alcohol dosages. Forty-two male undergraduate social drinkers, ages 18 to 25 years, were led to expect either alcohol or tonic. After actually consuming no alcohol, a low dosage, or a moderate dosage, they performed various cognitive and motor tasks. A questionnaire assessed subjects' responses to the expectancy manipulation and either preceded or followed task administration. A 2 X 3 X 2 multivariate analysis of variance resulted in a significant Expectancy X Dosage interaction for cognitive tasks (letter cancellation, digit span, Raven's matrices); subjects apparently compensated for alcohol-induced deterioration on these tasks when they were aware they had consumed alcohol. No consistent effects were found for motor tasks (finger tapping, stylus monitoring, standing steadiness, walking steadiness). The significance of the alcohol compensation effect and related methodological considerations are discussed.