Naturalistic drinking and driving: expectancy effects and acute protracted error with moderate alcohol consumption
Previous research has demonstrated biphasic effects of alcohol consumption on performance; some responses are more impaired on the ascending limb of the intoxication curve when blood alcohol concentrations (BACs) are increasing, and others are more impaired on the descending limb (when BACs are decreasing). It has also been suggested that well-practiced automatic responses are more resistant to alcohol impairment and may show improved performance on the descending limb (acute tolerance). The present research investigated these effects in the context of a naturalistic alcohol consumption protocol in which drinking occurred in social groups over a period of four hours. Forty-four participants were assigned to one of two alcohol dose conditions or a placebo control group and consumed alcohol in groups of three such that they gradually reached their target BAC (.05 or .08) and maintained it for one hour. The participants completed a series of cognitive tests (Cogstate test battery) and a simulated driving task (Driver Attention Inhibition and Reaction test) over the course of their intoxication curve. The results showed strong placebo effects on self-ratings of intoxication. No evidence of acute tolerance was found in driving performance, instead speed management showed acute protracted error, greater impairment during the descending limb. The findings provide strong evidence of expectancy effects in contributing to perceptions of intoxication but do not support the idea that well-practiced automatic behaviours may be resistant to alcohol impairment.