Locus of Control and Perceived Alcohol Ingestion in Performance of a Fine Motor Skill

Abstract

To investigate the influence of locus of control on a fine motor coordination task where subjects had ingested or believed that they had ingested alcohol, 60 men who were enrolled in introductory psychology and scored in the upper or lower thirds of the population on Rotter's I-E Scale (30 external and 30 internal scorers) were randomly assigned to one of three treatment conditions: a control group (no alcohol expected/no alcohol received), an alcohol group (alcohol expected/alcohol received), and a placebo group (alcohol expected/no alcohol received). Pretest and posttest measures of performance on the Purdue Pegboard Test were obtained from all subjects. Subjects in the control groups were given three 6-oz. (177.4-ml) glasses of fruit punch over a 35-min. waiting period between pretest and posttest on the Purdue Pegboard. The alcohol groups drank a sufficient number of similar glasses (usually three) to produce a 0.1% measure on a breathalyzer before completing the posttest on the Purdue Pegboard. The placebo groups were told that they were drinking an alcohol-based drink but were served three glasses of a nonalcoholic, rum-flavored fruit drink. These groups were also told that they measured 0.1% on a breathalyzer. Control groups, both internal and external scorers, showed essentially no change from pre- to posttest on the Purdue Pegboard. The alcohol groups, on the other hand, both internal and external scorers, showed a significant decrement in performance. The internal-placebo group did not differ from the two control groups and showed no decrement in performance. The external-placebo group, however, did not differ from the two alcohol groups and showed a significant decrement in performance at posttest on the Purdue Pegboard, despite the fact that they had ingested no alcohol. This supported the hypothesis that the external scorers who believed they had ingested alcohol would behave as though they had.