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by Kirsten Keane
April 05, 2010
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In good taste: Research explores food preferences

“You can have your dessert after you finish four more bites.” Most people have heard this phrase at one time, and many become the bearers of this torturous command years later as parents. But research shows this tactic isn’t particularly effective. So how do we get kids to eat their veggies, and even like them? Are kids who hate vegetables doomed to become meat-and-potatoes adults? And what makes some people actually love Brussels sprouts, anyway?

If a child doesn’t like a certain food, many parents don’t spend much time getting her to actually eat it. “It takes about 10 times to get a kid to like a new food—so don’t give up!” says ASU provost and psychology professor Elizabeth “Betty” Capaldi.

Capaldi has long studied what foods people like, and why. She runs a lab dedicated to food preferences within ASU’s Department of Psychology.

“The worst thing parents can do is tell their kids they can have dessert after they finish their vegetables,” she says. “This makes veggies even less appealing in comparison to the sweet treats awaiting them when they finish.”

Capaldi has shown this same contrast effect in her lab using rats. If the rats received a dessert after a vegetable, they liked the veggie less. “String beans are not as tasty as candy, but compared to liver, they might be good,” she notes. Of course, telling children if they finish four more bites of their veggies they’ll get to eat liver doesn’t motivate them to finish the first, either.

Capaldi shares another approach. “One way to get a child to eat her veggies is to mix it with food she already likes—such as mixing peas in mashed potatoes,” she says. “But an idea that is not as intuitive: sprinkle sugar on veggies like broccoli, and after about ten trials this way, the child should be able to eat the broccoli plain—and enjoy it.”

What about those grownups who aren’t good at eating their vegetables?

Your food preferences are pretty much learned, Capaldi says. There are genetic preferences for sweet and salty tastes and genetic dislikes for bitter and sour. But beyond that, we eat according to habit.

“It’s really important for people to understand that you can learn to like anything,” Capaldi says. “You can change your eating habits, and you can change what you like.”

This is good news, because meat-and-potatoes types are at risk for health problems if they can’t change their eating habits. Folks with a lackluster attitude towards veggies receive fewer antioxidants in their diets, and are more susceptible to cancer.

While most tastes are learned, some adults are predisposed to be picky eaters. This group, called supertasters, is more sensitive to the bitter taste often present in vegetables. In her lab, Capaldi has strips of chemical-treated paper that help her identify supertasters. The strips taste incredibly bitter to people in this group.

The psychology of taste is a relatively new field, emerging in the 1980s. At the time, researchers primarily focused on the external effects of food. It was believed that we ate when we were hungry and that hunger was solely based on the biological necessity to eat. But food isn’t just a physiological requirement borne of the evolutionary desire to live and reproduce. According to Capaldi, we of course eat for pleasure as well. “We eat in part because the food tastes good, and it’s fun to eat.”

“What makes food taste good?” she asks. “That’s my field.”

Capaldi started as traditional animal researcher, studying learning principles in rats. “Like many other researchers, we had rats in mazes pressing bars,” she says. “But what they really cared about was the food. They acted differently depending on the kinds of food they were fed.” This led Capaldi to expand her research to food learning and preferences.

Experiments with rats are often easier to conduct, and produce simpler theories, than human trials. Many of the principles involved in the psychology of taste are easier to discover and study in animals, but there are a lot of qualities of taste preferences that are unique to humans. As a result, much of Capaldi’s recent research has used 5-year-olds and college students as the subjects.

One area she studies is the concept of meals versus snacks. The research shows that if someone thinks a certain food is a snack, they will eat greater amounts later than someone who thinks of that same food as a meal.

“If you think something’s a snack, you’ll eat incredible amounts as opposed to a meal,” Capaldi says.

Even though the amount of calories in a meal is often much less than in a bag of potato chips, it’s easy to sit and not notice we’ve finished the chips until our fingernails scrape the bottom of the bag. Meals, on the other hand, are portioned and we finish when the plate is empty.

“We learn how much to eat by what we think it is, how filling we think it is, how many calories we think it is, and what we’re used to eating,” Capaldi explains.

Even rats eat differently depending on whether food is perceived differently. Little pieces of food seem like more to them, and they eat less.

Capaldi’s studies have been funded by the National Institute of Mental Health and the National Science Foundation. Her research costs are inexpensive these days. For experiments on snacking, often the only expenses are the ingredients to make a peanut butter sandwich. Other research expenses include chocolate pudding and chocolate cake.

Capaldi’s future research plans are centered on learning associated with preferences regarding food texture. This encompasses cognitive processes associated with preferred textures, as well as memory for food.

Overall, Capaldi’s goal is to teach people how to change their eating habits by changing what they eat. In order to accomplish that, she says, we need to buckle down and become comfortable eating healthier foods.

“Familiarity takes time,” she says. “But I think it’s empowering to know you can change yourself. You’re not a prisoner to what you eat.”

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