Washington, Nov. 8 (Reuters): Just two glasses of wine can cloud a person’s judgement so much that he does not even realise he is making errors, Dutch researchers have reported.
At a blood alcohol level of .04 per cent — reached by drinking two glasses of wine in less than an hour — the brain’s “oops” response stops working properly and people no longer realise they have made a mistake, the researchers said.
Richard Ridderinkhof of the University of Amsterdam in the Netherlands, who led the research, said his team monitored an area of the brain called the anterior cingulate cortex.
“We have known for some time that the anterior cingulate cortex is heavily involved in judgement,” Ridderinkhof said in a telephone interview.
“With the anterior cingulate cortex there is this component that you can see when you record an EEG (electroencephalogram),” he added.
“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’s team tested 14 men who were all social drinkers.
They gave them either an alcohol-free wine, enough wine to raise their blood alcohol levels to .04, or enough to get them fairly tipsy at .10 per cent.
Then the men took a computer test. They were rehearsed on the test, which involved reacting to an arrow on the monitor screen, so they did not make many mistakes, but their brain activity was recorded.
The men who had drunk any alcohol at all made more mistakes anyway, but their brains failed to react to them, Ridderinkhof’s team reported in today’s issue of the journal Science.
The differences were not much more pronounced at a .10 level than they were at a .04 level.
“We were really surprised to find this at a .04 level,” Ridderinkhof, a psychologist, said.
A .04 level is reached, for the average man, by drinking two glasses of wine, two small beers or two small servings of spirits in an hour.
Women reach that point somewhat sooner, Ridderinkhof said, and in general are more impaired at any level than men are.
This could have implications for drinking and driving laws, he said.
“Whereas it is difficult to generalise to a real-life situation, until we know more precisely a cut-off point, this certainly would be an indication that drinking and driving together is not a good combination,” he said.
It is well documented that even one drink can cause a person’s reactions to slow down, and that people who have alcohol in the blood make more mistakes on a variety of tasks.
Ridderinkhof said his team’s study shows that alcohol compounds these shortcomings, by suppressing the brain’s ability to catch errors and make up for them.
Usually after a person makes an error, he or she slows down and works much more carefully.
“However, after drinking alcohol this sort of control mode is diminished. It's almost gone,” Ridderinkhof said.