Abstract

Design aspects and results of experiments that investigated the effects of caffeine on alcohol-induced performance decrements in humans are discussed. Simple conclusions concerning those outcomes are unwarranted because they seem to depend on the tasks used and the dosages of both drugs, with both antagonism and potentiation of alcohol-induced effects having been reported. Results indicate that legally intoxicated individuals cannot antagonize alcohol-induced, driving-related decrements with caffeine prior to driving an automobile, thought to be the major behavior for which caffeine is used in attempts to antagonize alcohol-induced decrements. We offer suggestions for research concerning subjects' habitual use or nonuse of caffeine and typical alcohol consumption levels, the interval between alcohol and caffeine ingestion, and the effects of caffeine and alcohol alone on performance tasks. We also suggest that statistical analyses should allow for a differentiation of results in which caffeine partially offsets an alcohol-induced decrement from more positive results in which caffeine returns functioning to its normal level.