Soup's on

Natural History, June, 2005 by T.J. Kelleher

Knowing whether you're hungry or sated should be a classic case of gut intuition. Yet a recent study of eating habits showed that people don't pay much attention to the gut: they rely instead on their eyes

to assess whether they've eaten their fill.

Brian Wansink, a food-marketing psychologist at Cornell University in Ithaca, New York, and two colleagues set out to determine whether people can be tricked into eating more than they intend to (yes, they can) and whether, once tricked, they have a good idea of how much they actually ate (no, they don't).

At lunchtime in a university cafeteria, the investigators seated volunteers in groups of four at a modified table, set with four eighteen-ounce soup bowls. Two bowls were ordinary, but two were covertly connected by a hose to a vat of soup, and very slowly refilled as the volunteers ate. Those spooning their soup from the ordinary bowls ate, and correctly thought they had eaten, slightly more than eight ounces. The deceived diners ate nearly fifteen ounces, on average, but thought they had eaten less than ten.

In both groups, similar proportions of the volunteers claimed they knew how much they had eaten. Most of them estimated their intake from the height of the soup in the bowl, and described their fullness after the meal in similar terms. Apparently--the adage notwithstanding--the eyes are really smaller than the stomach. (Obesity Research 13:93-100, 2005)