Cognitive processes and motor skills differ in sensitivity to alcohol impairment

Research reviews have suggested that cognitive and motor skills are not equally sensitive to a moderate dose of alcohol; they disagree, however, on which type of task is more sensitive to impairment. This issue is addressed in two experiments testing a cognitive and a motor skill task performed by the same person at comparable blood alcohol concentrations (BACs) during a moderate dose of alcohol.

A motor skill task (PR) and a rapid information processing (RIP) task requiring no learned motor skill were performed in counterbalanced order, and tests on the pair of tasks occurred at intervals as BAC rose and declined. In the first experiment, two groups of male social drinkers (each n = 10) received either a moderate dose of alcohol (0.62 g/kg) or placebo and performed the tasks with no consequence for performance. The second experiment comprised four groups (each n = 14) to verify and extend the results to a situation in which unimpaired performance under alcohol was rewarded on one or both tasks.

In both experiments, impairment on the PR task tended to increase and diminish with rising and declining BACs, whereas impairment on the RIP task showed no such pattern. Reinforcement reduced the degree of impairment displayed on each task, but the different task profiles of impairment were still evident.

The results indicate how disagreement over the sensitivity of cognitive and motor skills to a moderate dose of alcohol may occur when impairment is only assessed at some particular BACs. Theoretical and practical implications of the findings are discussed.