Before you down that pint, check the shape of your glass—you might be drinking more beer than you realize. According to a new study of British beer drinkers, an optical illusion caused by the shape of a curved glass can dramatically increase the speed at which we swill.
Binge drinking is on the rise says experimental psychologist Angela Attwood of the University of Bristol. There is a proportionate rate in the increase of crime to alcohol consumption. Attwood suspected that the shape of a beer glass, which can give the appearance of different volumes to the same amount of liquid, might also distort perception of how much alcohol is being consumed.
To test the hypothesis, she and her colleagues randomly divided 160 young, healthy people—students and faculty members of the University of Bristol, as well as some members of the general public—into eight groups. Volunteers were easy to get. FREE BEER AND LEMONADE tends to convince persons to be guinea pigs. They were then video recorded drinking. They assigned each group to drink either lager or soft drink from straight or curved glasses. While the participants drank, they watched a nature documentary deemed emotionally neutral, so that they wouldn’t be “sitting there with nothing to do but drink,” Attwood says.
After watching video of both sessions and recording how much time it took for the drinkers to finish their beer or sodas, Attwood’s team found that one group consistently drank much faster than the others: the group drinking a full glass of lager out of curved flute glasses.
Attwood believes that the reason for the increase in speed is that the halfway point in a curved glass is ambiguous. Social beer drinkers, she says, naturally tend to pace themselves when drinking alcohol, judging their speed by how fast they reach half-full. Another experiment in which participants were asked to judge different levels of fluid in photographs of straight and curved glasses showed that people consistently misjudge the volume in fluted glasses, Attwood says.
Not included in the study? Drinking from cans. Drinking from bottles. Drinking from Red Solo Cups at parties.