Effects of outcome expectancies and disinhibition on ad lib alcohol consumption

The present study was designed to demonstrate a causal role for alcohol expectancies in alcohol consumption by experimentally manipulating expectancies and measuring ad libitum consumption in the laboratory. A second goal was to determine whether effects of expectancy manipulation on alcohol consumption would differ as a function of disinhibition, a trait often associated with increased risk for alcohol-related problems.

Male nonproblem drinkers (N = 120) completed measures of preexisting expectancies, disinhibition and typical alcohol consumption; were given expectancies for the effects of alcohol on a novel task for which they were paid based on their performance; and participated in an ad lib drinking session.

Subjects who were told that alcohol would impair task performance expected greater impairments in performance (p < .001) and consumed less alcohol (p < .05) than subjects told that alcohol had no effect on performance and those told that the effects of alcohol were unknown. Differences in alcohol consumption across groups were mediated by expected effects of alcohol on task performance. Subjects scoring higher in disinhibition expected more negative effects of alcohol in the impairment condition than in the other conditions, whereas subjects scoring lower in disinhibition did not expect differences in the effects of alcohol across the three conditions.

Alcohol outcome expectancies were effectively manipulated and a causal effect of expectancy on alcohol consumption was demonstrated. This was the first demonstration of a causal effect of expectancy using a behavioral measure of alcohol consumption.