Judging when alcohol's effects wear off not easy

The way that alcohol impairs reasoning and problem-solving abilities may explain why some people feel they are fit to drive even though they are drunk.

To look at how cognitive abilities, which affect thinking skills, are affected during both rising and declining levels of blood alcohol concentration (BAC), researchers made 20 Americans consume alcoholic drinks over an eight-hour period to bring their BAC up to 0.10 percent and then waited for their levels to return to a normal BAC. BAC is a measurement used to determine intoxication, usually for legal or medical purposes. As their BAC levels rose and then fell during the experiment, the participants were asked to describe their feelings of drunkenness and they were assessed on their ability to navigate a hidden maze learning task on a computer.

Sober young adults made few mistakes on this test. But in this experiment, errors increased dramatically with rising BAC levels and the rate of errors did not decline dramatically even when the participants said they felt less drunk. The type of cognitive functioning used in the computer test is important for driving skills and making judgments in terms of travelling through intersections or changing lanes, the researchers noted.

The findings show that executive function does not recover as quickly after drinking as basic functions such as motor speed and information processing speed.