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One stiff drink, or two glasses of wine, can cause drinkers to begin making mistakes and not recognizing that they have made an error, according to a new study from the University of Amsterdam.
A blood alcohol content of only .04 can impair the ability to reason quickly and detect errors, the study concluded, supporting the long-held belief by activists that impairment begins long before the legal BAC limit for drunk driving.
In the Amsterdam study, Richard Ridderinkhof and his associates studied what they call the brain's "oops" response which can be monitored electronically in an area of the brain called the anterior cingulate cortex (ACC).
"We have known for some time that the anterior cingulate cortex is heavily involved in judgment," Ridderinkhof said. "With the anterior cingulate cortex, there is this component that you can see when you record an EEG [electroencephalogram]. Some people call it the `oops' response. This is really there when you make an overt error, then you see this brain wave - and it is not there when you give a correct response.''
Ridderinkhof tested 14 men who were social drinkers. They were given either an alcohol-free drinks, enough alcohol to raise their blood alcohol levels to .04, or enough to get them legally "drunk" at .10 percent. The men took a computer test, which involved reacting to an arrow on the screen, and their brain activity was recorded. They were given the opportunity to practice taking the test before they were given alcohol.
The volunteers who did not drink any alcohol experienced an error rate of about 4.8 per cent, but after the first drink the error rate increased to 19.8 per cent. The time each subject took to decide the correct answer also increased when they drank alcohol. All of the subjects who drank alcohol made mistakes, but the number of mistakes at .10 level were not significantly different from those at a .04 level. "We were really surprised to find this at a .04 level," Ridderinkhof told reporters.
Perhaps more importantly, the research indicated that at .04 the subjects did not recognize that they were making mistakes, according to the electronic response in their ACC.
"Whereas it is difficult to generalize to a real-life situation, until we know more precisely a cutoff point, this certainly would be an indication that drinking and driving together is not a good combination," Ridderinkhof said.
The study was published in the journal Science.
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