STEVE INSKEEP, HOST:
The most recent studies show that American kids still have a problem with obesity. In fact, the closest thing we have to good news is that kids are not gaining weight as rapidly as they were some years ago.
Some experts say fast food and a lack of exercise drive childhood obesity in the United States, and now researchers at Cornell University may have identified a surprising new factor. NPR's social science correspondent Shankar Vedantam is here to tell us about it. Hi, Shankar.
SHANKAR VEDANTAM, BYLINE: Hi, Steve.
INSKEEP: OK. What's the problem?
VEDANTAM: I can say it in one word, Steve: plastics. In this case, plastic debit cards might be making our kids fat.
INSKEEP: What do you mean by that?
VEDANTAM: Well, many school cafeterias allow kids to pay for their lunch by swiping a debit card. You know, your parents load up $50 on the card and the kids swipe it in the cafeteria.
VEDANTAM: I spoke with Brian Wansink. He's a behavioral economist at Cornell, so he studies how human behavior affects economic choices. He's found that compared to kids who use cash in cafeterias, kids who use debit cards seem to make more unhealthy eating choices. Here he is.
BRIAN WANSINK: Kids are much, much, much more likely to take desserts, and are much less likely to take fruits and vegetables. In contrast to that, in schools where kids are paying cash, kids not only buy a lot more fruit, but they also buy a lot less dessert.
INSKEEP: Wow. OK. A lot of questions there, one of them why. But first, how is it that he knows this?
VEDANTAM: Well, along with a colleague, David Just, Wansink has just finished an analysis where he monitored more than 2,300 students at 287 schools across the country, kids in grades one through 12. And what they found was that three times as many kids buy vegetables when they were paying cash, rather than using debit cards, and kids paying cash also ate a lot less. They consumed 10 percent fewer calories.
INSKEEP: I want to try to figure this out because I think people instinctively understand you might spend more money with a debit card or a credit card. That's one reason a lot of people don't like to use them very much. You feel that maybe you're going to be more careful with your money if money is going through your hands. But you're not necessarily talking about kids spending more or less; you're talking about them choosing different foods depending on how they paid. Why would that be?
VEDANTAM: Well, I think you've actually hit the nail on the head, Steve. Using cash and credit cards are the same in terms of economics, but psychologically they're actually very different things. When you're using a debit card or a credit card, the consequences, the financial consequences of your purchase, are far off in the future.
And Wansink thinks the same thing might be happening with your experience of the things that you buy, which is your attitude becomes, what I put in my mouth doesn't really matter because the consequences of that are also far off in the future.
INSKEEP: OK. If schools are concerned about childhood obesity, what should they do about this?
VEDANTAM: Well, Wansink thinks the smart thing to do is to actually work with the bias instead of trying to fight it. Once we understand how the bias works, why not make it work for you? So his idea is what if schools said you can buy fruits and vegetables using the debit card, but if you want to buy desserts and candy, you actually have to pay cash.
VEDANTAM: And he's also conducted another experiment along these lines. He's found that making it a tiny bit harder for kids to get cookies in a cafeteria makes a big difference to whether they actually pick out the cookies. Here he is again.
WANSINK: When we put cookies behind the line, behind the lunch line, so that kids have to ask the cafeteria workers to pass it to them, cookie sales dropped dramatically. In some cases as much as 50 percent, simply because a kid has to wait for 10 seconds to say can you please hand me a cookie.
VEDANTAM: So I think the bottom line here, Steve, is that it's hard to get through to kids when you, you know, you have to worry about coronary heart disease in 40 years. For a 17-year-old, that just is so remote.
VEDANTAM: It's much more effective to say, hey, look, all your friends are already sitting down and eating. They're already talking. Maybe they're talking about you. Wouldn't you rather be sitting down with them instead of spending 10 boring seconds waiting for a cookie?
INSKEEP: Well, Shankar, I've got a debit card here. Let's go get something to eat.
VEDANTAM: Absolutely, Steve.
RENEE MONTAGNE, HOST:
NPR's science correspondent Shankar Vedantam. You can follow him on Twitter @hiddenbrain. You can follow this program @morningedition and @nprinskeep.
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