A Field Experiment on the Impact of Incentives on Milk Choice in the Lunchroom

Almost a third of US children ages 2-19 are deemed overweight or obese, and part of the problem is the habitual decision to consume high calorie, low nutrient foods. We propose that the school lunchroom provides a 'teachable moment' to engage children in making healthful choices. We conduct a field experiment with over 1,500 participants in grades K-8 and evaluate the impact of small non-monetary incentives on the selection of milk in the school lunchroom. At baseline, only 16% of children select white milk relative to 84% choosing chocolate milk. We find a significant effect of incentives, which increase white milk selection by 2.5 times, to 40%. One concern with incentives is that they may decrease intrinsic motivation to eat healthy, called 'crowd-out of intrinsic motivation.' However, we do not find evidence of 'crowd-out'; rather, we see some suggestive evidence of the positive habit forming effect of incentives.