CHAMPAIGN, Ill. -- If you are what you eat, do you eat whatever's before you? Apparently so, at least when it comes to snack foods where size has become a major ingredient in marketing.
On Feb. 6, Brian Wansink, a professor of business administration at the University of Illinois, took eight graduate students from his Food & Brand Lab on campus to a movie theater in Mount Prospect, Ill. They gave out large and extra-large popcorn containers to people attending a matinee showing of "Payback," starring Mel Gibson. Afterward, Wansink and the students weighed the containers to see how much the moviegoers ate.
People given the extra-large containers ate 44 percent more than those handed the slightly smaller containers.
CBS "This Morning" taped Wansink and his students for a report on the impact of portion size on the weight and diet of Americans. Wansink found that the extra-large size added 120 calories to the average intake of the moviegoer. "If you have it, you'll eat it," he said.
Until now there has been little scientific research on why large packages increase consumer usage. Generally the link was believed to be based on the "scarcity effect" -- people used more from large packages because they worried less about running out.
Wansink has been testing another theory -- that people use more from larger packages because the product is perceived as cheaper. Wansink has run five studies using liquid cleaners, cooking oils, spaghetti, bottled water and bleaches. In the first four experiments, consumers were observed at his Brand Lab using different sizes of the same products. The fifth experiment was conducted to prove the lab findings were applicable to the real world. Altogether, 691 adults were tested.
The results were similar to the popcorn test. "People use more from larger packages -- typically between 9 percent and 36 percent more -- because, deep down, they perceive that per-unit cost is cheaper in large packages. We further found that increased package size works best with food and household products that are used frequently and are familiar to consumers."
There was, however, an upper limit to the package-usage relationship. "After a certain point, increasing package size will have no effect on usage," Wansink said. This was especially true among products with potentially harmful side effects from overuse, such as bleach.
Wansink set up his Food & Brand Lab, believed to be the only such research facility at a U.S. university, two years ago to examine consumer behavior with commonplace packaged foods and household items.
"Letting people know about the subtle things that influence their behavior helps them become better consumers," Wansink said. "This has been a major objective of my research."