Rational choice theory commonly assumes that the presence of unselected choices cannot impact which among the remaining choices is selected—often referred to as “independence of irrelevant alternatives.” We show that such seemingly irrelevant alternatives influence choice in a school lunch setting. In these lunchrooms, we provide evidence that the presence of specific side dishes—trigger foods—can strongly increase the sales of unhealthy à la carte options, even when the trigger foods are not selected. This behavioral anomaly can be exploited to lead children to healthier choices. We also offer a method that can be used to identify such foods.
