Washington ? Even a single drink of alcohol is enough to impair someone’s ability to reason quickly and detect errors, according to a study that monitored brain waves in volunteers given drinks.

Dutch researchers put sensors on the scalps of 14 men who were tested in three sessions after having a placebo, a single alcohol drink or several drinks. The volunteers then were challenged in a computer test that required quick thinking and instinctive reasoning.

Changes in brain action were quickly detected even after a single drink, leading the researchers to conclude that alcohol, even in “modest doses,” was enough to erode the mind’s ability to detect and correct errors.

The alcohol was administered using orange juice spiked with vodka containing 37.5 percent alcohol. The dosage was based on the weight of the test subject. For instance, a 180-pound man would be given drinks with an alcohol content of 1.2 ounces for a low-dose test and about 2.4 ounces in a high-dose test. The drinks were consumed over a 20-minute period.

The lead author on the study is K. Richard Ridderinkhof of the University of Amsterdam and the Leiden University. It was published electronically Thursday by Sciencexpress, the online edition of the journal Science.

Ridderinkhof and his colleagues tested the volunteers using a technique that measures the ability to respond correctly to conflicting and confusing signals.

On placebo, the volunteers experienced an error rate of about 4.8 percent, but after the first drink the errors soared to 19.8 percent.

Drinking alcohol also reduced processing speed, the time each subject took to decide the correct answer.

Measures of brain waves showed the small doses of alcohol quickly affected the anterior cingulate cortex, a part of the brain that influences thinking processes and the unconscious detection of error.