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Bottoms Up! The Influence of Elongation & Pouring on Consumption Volume

Wansink, Brian and Koert van Ittersum (2003). Bottoms Up! The Influence of Elongation and Pouring on Consumption VolumeJournal of Consumer Research, 30(3), 455–463. doi:

Beware of the shape of glass you use. It could contribute to you drinking much more than you think. Two studies of 167 people showed that both children and adults pour and consume more juice when given a short, wide glass compared to those given a tall, narrow glass, but they perceive the opposite to be true. *

The studies, conducted by researchers at the Food and Brand Lab went to a Health and Fitness Camp for teenagers and gave campers either short wide glasses as they entered the cafeteria line or tall, slender glasses. Both glasses held 22 ounces. As the campers exited the line, they were stopped and asked how much soda, milk, or juice they had taken and their glass was measured. People given short wide glasses poured 76% more than those who had randomly been given tall slender glasses. They believed, however, that they had poured less. The same was true when the study was repeated with adults.

This bias is caused by a visual illusion known as the vertical–horizontal illusion. The tendency we have to focus on heights instead of widths. That's why, for instance, people say, "Boy, is the St. Louis Arch high," but they never say, "Boy, is it wide," even though the dimensions are identical.

When pouring into glasses, we tend to focus on the height of the beverage and basically ignore the width," said Brian Wansink Ph.D. , an author on the study (along with Koert van Ittersum, Ph.D. ). "That's why we over pour into wide glasses but think we poured very little. "

A wide range of people and institutions would like to better control a person's consumption of a product. Those in the hospitality industry want to decrease costs (via serving size) without decreasing satisfaction. Those in public policy want to decrease waste. Those in health and dietetics fields want to decrease over–consumption. Those on restricted diets want to decrease calories, fat, or sugar intake. If short, wide glasses encourage people to pour more than tall glasses, the selection of glasses has an impact on costs as well as on calories.

Yet there are circumstances where there is a desire to stimulate an increased consumption of healthy beverages with the undernourished young and old. For instance, a parent may want to encourage their child to pour and drink more milk at home, and a dietician may want nursing home patients to consume more juice in the cafeteria. In these cases, short, wide glasses would encourage more consumption than the narrow six ounce glasses that are often provided.

Download the article here. 

*The study was conducted at the University of Illinois, former location of the Cornell Food and Brand Lab.