It's common knowledge that a brain on booze doesn't function as well as a sober one. After drinking, people demonstrate slower reaction times and make more mistakes. Now research published online by the journal Science suggests that moderate drinking also interferes with a person's ability to recognize when he has committed an error.

K. Richard Ridderinkhof of the University of Amsterdam and his colleagues recruited 14 male social drinkers to test alcohol's effects on a region of the brain known as the anterior cingulate cortex (ACC). The ACC is involved in detecting erroneous or conflicting responses. The men performed a so-called flanker task, in which they were asked to identify the direction of a target arrow that was surrounded by other arrows meant to distract them. After being trained on the test, the subjects consumed two drinks (either placebo or alcoholic) in under an hour and performed the tasks again while their brain activity was monitored. Specifically, the scientists analyzed the error-related negativity (ERN) response and found that men with blood alcohol levels of 0.04 percent and 0.10 percent showed significantly lower ERN responses than their sober counterparts did. That is, the drinkers' brains were not as good at noticing mistakes. And unlike their sober counterparts who slowed down after making a mistake to try to correct their actions, men who had imbibed alcohol showed no signs of such corrective behavior.