Effect of ethanol on judgments of performance.

Ethanol impairs cognitive and psychomotor performance, although the precise reasons for this remain unclear. We investigated the effect of ethanol on individuals' judgment of their performance. Eighteen healthy volunteers (19-22 years) received a high dose of ethanol (0.8 g/kg for males and 0.7 g/kg, for females), a medium dose (75% of the high dose) and a placebo in counterbalanced order on three study days. A general knowledge (GK) test was administered on a pen computer 75 min after the drink. An adaptive algorithm adjusted the difficulty of questions so that scores were similar on all three study days. Volunteers then rated how well they believed they had performed the GK task using a visual analogue scale. A battery of other performance tests and mood ratings was also completed both before and after the GK test. These showed the expected effects of ethanol. There were no significant differences in scores on the GK test between treatment sessions. There was a highly significant dose-dependent increase with ethanol on volunteers' ratings of their performance on this test. These findings suggest that ethanol leads to an overoptimistic assessment of ability which may contribute to ethanol's impairment of performance.