Here is a parable for our time: There once was an adult who wanted to encourage eighth graders to eat healthier food. The adult designed a lesson plan full of nutritional information—why fruit and vegetables are good for you, why junk food is bad for you, and so on. A similar approach had worked with younger children. But the eighth graders declared the intervention—and, if we’re being honest, the adult—boring. They carried on eating junk food, some of them in greater quantities than they had before.