Effects of alcohol, instructions and consumption rate and motor performance.

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Abstract
To investigate the combined effects of alcohol, instructions regarding the alcohol content of a beverage and the rate of consumption on motor performance, 64 men college students (mean age 19) completed a pursuit rotor tracking and a divided-attention task consisting of simultaneous performance of the pursuit rotor-tracking and reaction-time tasks before and after drinking. According to the Quantity-Frequency-Variability Index, 53 were heavy and 11 were moderate drinkers. Each subject completed a short questionnaire estimating the expected effects of intoxication on motor and reaction-time tasks. In a balanced placebo design, half of the subjects were told they would be given an alcoholic beverage and half that they would be given a nonalcoholic beverage; half of each group received an alcoholic beverage and half received a nonalcoholic placebo. Half of those in each of the 4 instructional set-beverage groups were told to drink their beverage in 15 min (0.45 g of alcohol per kg of body weight) and half in 45 min (0.49 g/kg). Pursuit rotor-tracking performance, alone and during the divided-attention task, was adversely affected by a moderate dose of alcohol, the subjects drinking alcohol being on target for less time than those given a placebo. Reaction time was not affected by alcohol, and, perhaps because blood alcohol concentrations reached only 0.04%, the drinking rate had little effect on performance. Instructional set did not influence any of the measures of performance, but instructions and beverage influenced the subjects'' estimates of intoxication, the beverage being more important than the instructions.