The Shape of Your Beer Glass Is Making You Drunk

Beer served in a pint glass may lead to more drinking then intended. Nick Purser/Getty

Your drinking glass can trick you into consuming alcohol much more quickly than you intended.

That's because, according to new work by researchers at the University of Bristol in England, people tend to make volume judgments based on the height or shape of a container—and they are often pretty far from the mark. When the glass holds OJ, those terrible guesstimates don't really matter. But they become a serious problem at the bar.

To better understand what makes people overindulge, David Troy, a Ph.D. student at Bristol, and his fellow researchers recruited drinkers and split them into two groups. Half received glasses with lines marking where it was a quarter, half and three-quarters full; the other group had the same glasses but without the indicators. Those drinking from marked glasses imbibed more slowly than the other group—suggesting, the researchers say, that when drinkers have a clear view of how much they're consuming, they pace themselves.

To test the effect of glassware shape on volume judgment, researchers asked volunteers to complete a computer task designed to measure their ability to judge the true volume midpoint of a liquid in two glassware silhouettes: one with curved sides and one with straight. Perhaps unsurprisingly, participants were far more likely to misjudge the halfway point of a curved glass than that of a straight glass.

Lastly, the researchers took their study out on a bender. They asked three bars to record how much beer they sold over the course of two weekends when using two different kinds of glasses: one straight and one curved. It turned out that straight-sided glasses led to significantly fewer purchases. The paper that resulted from the work, presented recently at the 2015 British Psychological Society Annual Conference in Liverpool, argues that the bar patrons served in the straight glasses ended up drinking less because they were better than those barflies with curved glasses at judging the volume of their beverages.

"Human behavior is not actually driven by deliberation upon the consequences of actions, but is automatic in response to their environments," says Troy. Environmental cues like color, size and, in this case, shape of glassware can influence how we experience drinking. Speciality beer glasses with curves—the Belgian dubbel chalice, the German pilsner beer boot, the India pale ale snifter—may make the drink taste better, but they are also great at convincing bar patrons they've drunk less than they actually have. And the more they drink, the worse their perception gets. All of which leads to excess drinking.

Dr. Pamela Peeke, a physician and senior science adviser at Elements Behavioral Health, a addiction and mental health treatment provider, suggests simple changes can nudge individuals to make healthier choices. "Use tall, narrow glasses when alcohol is poured. People think they're drinking more when they're not, in comparison to short, wide or curved glasses," says Peeke. "It's all a mind game."