Heavy drinkers tend to think that they’ve attained some sort of practice and are better able to handle themselves while drunk. But previous research shows that alcohol hinders motor coordination and the brain’s cognitive functions. What scientists didn’t know was exactly how tolerant someone could become to alcohol.

Now, in a paper published in the journal Psychopharmacology, a team of scientists explain that while heavy drinkers are comparable to light drinkers when it comes to fine motor skills, they’re actually worse at tasks pertaining to short-term memory, motor speed, and other complex cognitive processing tasks. While heavy drinkers report lower self-perceived impairment — also known as “behavioral tolerance” — they’re not necessarily more sober.

“Overall, there is a common belief among heavy drinkers that they can ‘handle their alcohol’ and that many common daily tasks may not be affected by their alcohol use,” lead researcher Dr. Ty Brumback said in a statement. “The take-home message here is that tolerance to alcohol is not equal across all tasks and is not protective against accidents or injuries while intoxicated, because it may in fact lead the heavy drinker to judge that they are not impaired and attempt more difficult tasks.”

Alcohol changes the brain's neurobehavioral processes. 

Brumback’s team examined previously collected data of 86 self-reported heavy drinkers and 69 light drinkers. The study is broken into two parts: In the first trial, both groups of drinkers were asked to do two psychomotor tasks, the Grooved Pegboard Test and the Digit Symbol Substitution Test (DSST). Participants were tested when sober and then again after given a dose of alcohol.

During the Grooved Pegboard Test, subjects were timed while they moved and inserted rotating pegs into slots in a board. This test is an analog for fine motor tasks, like using keys to unlock a door. The DSST involved participants trying to memorize a list of symbols that coordinate to numbers, then attempted to correctly fill in a sheet of paper coordinating those symbols and numbers within 90 seconds. The reasoning for this test is that it mimics a complex task that involves short-term memory, like actually driving a car.

Five years later, the same group of participants completed the same two experiments again. Overall, they found that every participant completed the tests better when they were sober.

But something did change over time: When it came to the pegboard test, heavy and light drinkers showed similar levels of impairment during the initial testing, but five years later both groups actually showed improvement. The researchers explain the heavy drinkers’ slight improvement to the fact that their brains showed evidence of an increased chemical tolerance to alcohol.

But while heavy drinkers may metabolize alcohol faster (leading to the ability to do fine motor tasks) each group still did a really terrible job with the DSST test during both test periods. Cellular adaptations may have helped heavy drinkers think they weren’t impaired, thus helping them out with the fine motor tasks, but DSST testing showed the reality of the situation: They were still too drunk to do anything complicated.

Dangerously, the scientists explain, the rewarding effects of alcohol combined with a sense that they aren’t that drunk is what leads heavy drinkers to still engage in risky behaviors. A heavy drinker might think they’re fine, but the beer goggles are still strapped on.

Photos via Wikimedia Commons, Giphy