Beer drinkers in the United Kingdom are influenced by an optical illusion caused by the shape of a curved glass. According to a new study published this month (August 17) in PLoS ONE, certain glass shapes can actually make people down a beer more quickly, possibly contributing to the rising binge drinking problem in the U.K. that legislation has failed to control.
Different glass shapes can give the same volume of liquid the appearance of varying volumes, reasoned experimental psychologist Angela Attwood of the University of Bristol. So she and her colleagues set out to test how much glass shape affected beer drinkers’ intake. They tested 160 healthy young people, who were categorized as “social beer drinks,” not alcoholics, according to the standard WHO test for hazardous drinking. The researchers then asked each participant to drink one of two volumes of lager or soft drink—either 177 milliliters or 354 milliliters—from either a straight or curved glasses, while watching a nature documentary. At the end of each session, the participants performed a word search task, the purpose of which was merely to throw them off the true purpose of the study.
Reviewing the data, the researchers found that people drinking a full glass of beer from a curved glass drank significantly faster—in about 8 minutes, compared to the average 13 minutes it took people drinking from a straight glass. They found no differences in drinking time, however, between curved and straight glasses of half a beer.
According to Attwood, social beer drinkers naturally pace their drinking by judging how quickly they reach the halfway point. Because a curved glass holds more beer in the top half, it unconsciously motivates drinkers to speed up, reasons Attwood, who suggests a solution of marking beer glasses with a half-full line. "We can't tell people not to drink, but we can give them a little more control," she told ScienceNOW.