Fast, but error-prone, responses during acute alcohol intoxication: effects of stimulus-response mapping complexity.
BACKGROUND
Although moderate doses of alcohol can impair performance on tasks that require information processing, little is known about the locus of the alcohol effects within the processing stream. This study used a psychological refractory period paradigm to investigate the effect of alcohol on the central, cognitive stage of information processing when task complexity is manipulated by altering stimulus-response compatibility.


METHODS
Thirty-four healthy male social drinkers were assigned to one of two groups (n = 17) that performed two tasks. Each trial consisted of a task 1 stimulus (tone) followed by a task 2 stimulus (letter) that was presented after one of four stimulus onset asynchronies (50, 200, 500, or 1100 msec). A baseline test of performance was obtained before the groups received a beverage containing either 0.0 g/kg (placebo) or 0.65 g/kg alcohol. Both groups were retested when blood alcohol concentration (BAC) was increasing and was decreasing.


RESULTS
The alcohol group made significantly more errors in task 1 compared with their drug-free baseline measure during the ascending phase of the BAC curve, and error rates increased to a greater extent for the more complex arbitrary stimulus-response mapping condition. Moreover, this increase in errors continued unabated during the descending phase of the BAC curve. Increasing BACs also slowed performance (longer reaction time), but unlike errors, reaction time returned to drug-free baseline levels when BAC was decreasing.


CONCLUSIONS
The results provide evidence that an acute dose of alcohol can impair one aspect of the central, cognitive stages of information processing. The possibility that errors in information processing remain during decreasing BACs even after processing speed has returned to drug-free levels has important practical implications relating to the detrimental consequences of acute alcohol intoxication.