The effects of expectancy and alcohol on cognitive-motor performance.

Previous studies have found equivocal evidence for expectancy effects on cognitive-motor performance. The effects of expectancy and alcohol on a dual tracking and reaction-time task analogous to some driving skills, and on choice reaction-time, were studied in a balanced-placebo design (n = 90). A dose of alcohol achieving 80 mg/100 ml (high dose) had large effects on both tasks, but a low dose (40 mg/100 ml) had no significant effects. Expecting alcohol led to subjects who received the high dose performing significantly better on the primary tracking task than subjects expecting placebo (but also receiving the high alcohol dose). By contrast, on a secondary reaction-time task, subjects who had received placebo performed worse 100-130 minutes after drinking, if they had expected alcohol. All groups felt more drunk than baseline and expecting alcohol made subjects feel more able to perform, whatever drink they had received. The implications of these findings for the nature of expectancy effects on performance and the relationship between expectations and strategy are discussed.