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Shape of beverage glass influences how much people pour – and drink
Mark
Reutter, Business Editor
217-333-0568; mreutter@illinois.edu
10/21/2003
CHAMPAIGN, Ill. —
Your eyes play tricks. And your brain makes it worse.
Both teenagers and adults misjudge how much they pour into glasses.
They will pour more into short wide glasses than into tall slender glasses,
but perceive the opposite to be true. The delusion of shape even influences
experienced bartenders, though to a lesser degree, a researcher at the
University of Illinois at Urbana-Champaign has found.
How shape can alter a person’s notion of size has been widely
investigated. For instance, triangles are generally perceived to be
larger than squares, and horizontal shapes are seen as smaller than
vertical objects of identical volume.
Yet research examining the effects of shape on how people determine
how much they consume is limited, said Brian Wansink, a professor of marketing and nutritional science at
Illinois. To understand the process better, Wansink examined how shape
influences teenagers, adults and bartenders who pour beverages into
empty glasses.
The results of his study will be published in the December issue of
the Journal of Consumer Research.
Wansink, director of the Food
& Brand Lab at Illinois, conducted three tests. In the first,
he looked at how much juice 97 teenagers poured for themselves during
breakfast at a summer camp in New Hampshire. The male and female campers,
12 to 17, with an average age of 15, had come to the camp to learn about
nutrition and lose weight. They were taught about dieting and portion
control in daily lectures and demonstrations.
Upon entering the cafeteria line for breakfast on the ninth day, the
campers were randomly given a tall and short glass of identical capacity
in which to pour their orange juice. The tall glass was slightly less
than twice the height of the small glass.
The teenagers poured 76.4 percent more orange juice in the short, wide
glasses than in the tall glasses (9.7 ounces versus 5.5 ounces). Although
the girls poured less juice in their glasses than the boys, both groups
equally overpoured in the short, wide glasses.
When questioned by Wansink’s team, however, the teenagers believed
that they had poured less (7 ounces) into the short, wide glasses, and
more (7.5 ounces) in the tall, slender glasses. This mistaken impression
translated into drinking more juice when placed in the short glass,
with 97 percent of all campers finishing the juice they had poured.
The psychologist Jean Piaget (1896-1980) believed that young children
tended to be caught and fixed by the vertical dimension of a visual
field. Piaget thought that as they grew up humans developed strategies
to isolate and better compare vertical and horizontal dimensions.
But the tendency to overestimate the vertical dimension persisted in
a second experiment conducted by Wansink. He used the same basic procedure
of the teenager study to measure how much juice was poured by 89 adults
eating breakfast at a camp in western Massachusetts. The group ranged
from 16 to 82, with an average age of 37.
The adults poured and consumed 19.2 percent more juice in the short
wide glass than in the tall slender glass (6.8 ounces versus 5.7 ounces).
“These results were consistent with Piaget’s notion that
older people are less likely to focus their attention merely on the
vertical dimension and are better able to account for the other dimensions
as well. Still age did not eliminate the elongation effect,” Wansink
wrote.
The adults, like the teenagers, mistakenly perceived that they had poured
less into the wide glasses than into tall, slender glasses. Seventy-nine
percent of the adults given the wide, short glasses underestimated how
much they poured, as compared with 17 percent of those given tall glasses.
When informed of the overpouring, most of the adults expressed surprise.
“We heard remarks like ‘You’re kidding’ and
‘Can you weigh it and show me?’ which is consistent with
the general lack of awareness by participants of how much they actually
poured,” Wansink said in an interview.
In a final study, Wansink examined how accurately bartenders could estimate
drink volumes. He asked 45 bartenders in Philadelphia to pour 1.5 ounces
of liquor into drink glasses. Half the bartenders were given slender
highball glasses, and the others had short tumbler glasses. Each glass
held 12 ounces. The bartenders were asked to pour rum for a rum and
Coke, whiskey for a whiskey on the rocks and vodka for a vodka tonic.
On average, the bartenders poured 31.3 percent more into the tumbler
glass than into the highball glass (2.1 ounces versus 1.6 ounces).
Less experienced bartenders tended to overpour more (2.2 ounces in tumblers
versus 1.6 ounces in highball glasses), but even bartenders with an
average of nine years of experience poured 1.8 ounces in the short glass
compared with 1.7 ounces in the tall glass.
There are various policy implications in these findings, according to
Wansink. The tricks of the eye and brain could play havoc with dieters
seeking to monitor and better control food and beverage consumption.
“Because people believe there is greater capacity in a tall, slender
glass, they will pour less into it, but thinking the opposite with a
short, wide glass, will keep pouring,” the researcher said. Aside
from overconsumption of alcohol, inadvertent overpouring of medications
and over-the-counter drugs could pose a potential health risk.
Wansink’s paper is titled, “Bottoms Up! The Influence of
Elongation on Pouring and Consumption Volumes.”
