Researchers at Cornell University published a "New Year's tip" in the latest issue of the British Medical Journal: the shape of a wine glass can affect the amount of wine poured and consumed. Even professional bartenders unintentionally pour 20% to 30% more into wider, shorter glasses.
Brian Wansink, a professor at Cornell University, said that people always pour more into wide, short glasses and less into tall, slender ones, a phenomenon that is not influenced by the pourer's education level, concentration, or practical experience. It is speculated that this might be caused by the "vertical-horizontal optical illusion," where people tend to perceive vertical lines as longer than horizontal lines of the same length. Wansink explained that when pouring, people tend to focus on the height of the liquid while neglecting its width.
Researchers had 198 college students (43% female) and 86 professional bartenders (with an average of 6 years of experience, 38% female) pour 1.5 ounces of Sprite into wide, short tumblers and tall, slender glasses, respectively. The results showed that the students poured an average of 30% more into the tumblers, while the professional bartenders poured 20% more. When the students were given repeated practice beforehand, they still poured 26% more into the shorter glasses. Even when the bartenders poured "at a leisurely pace," they still poured 10% more.
Wansink, the director of Cornell University's Food and Brand Lab, has long studied the psychology and behavior of eating and drinking. He suggests that people typically drink 92% of what is in their glass. Therefore, for those who wish to drink less, it is advisable to use tall, slender glasses or glasses with measurement markings. For parents, he recommends using tall, slender glasses for carbonated drinks for their children and wide, short glasses for healthy beverages like milk.