To expedite long lunch lines and enable cleaner accounting, about 80 percent of schools use debit cards or accounts that parents can add money to for cafeteria lunch transactions, write David Just and Brian Wansink, professors at the Cornell Center for Behavioral Economics in Child Nutrition Programs.
"There may be a reason for concern about the popularity of cashless systems," say the researchers. "Debit cards have been shown to induce more frivolous purchases or greater overall spending."
Just and Wansink compared purchases at school cafeterias that use debit-only systems with those that accept debit or cash. They found that students in first through 12th grades at debit/cash cafeterias consumed about 721 calories compared with 752 calories at debit-only schools.
For non-healthy food items alone - such as candy, dessert, cheeseburgers and fries - students at debit-only schools consumed 441 calories during their lunch, compared with 378 calories for students at debit/cash schools.
An ice cream sandwich here and a bag of potato chips there add up: A child can draw down debit accounts quickly, the research points out. Parents pay for several weeks' worth of lunches in advance, often with little control over individual transactions. Parents often have difficulty gauging how long the money should last, if spent wisely.
"This may lead children to generally greater spending on lunch," the researchers report.
The results, which are based on a study of more than 2,300 students, have important implications for schools and child obesity. A small number of schools have introduced debit systems that allow parents to regulate daily spending, which can help combat the problem. If the use of cash, as opposed to debit cards, can nudge a student into making slightly healthier choices, then perhaps a "cash-for-cookies" policy, for example, would "encourage students to think twice before making their selection," said Just and Wansink.
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