Almost a century ago, the psychologist Jean Piaget defined the stages of cognitive development. Up until about age 2, children learn about cause and effect through their actions. For the next five years, they learn through pretend play but struggle with logic. By middle school, they're in the "concrete operational stage." Their thinking is more logical but still rigid. Then around age 12, children enter the "formal operational stage," becoming capable of theoretical and abstract reasoning. This progression isn't just about acquiring knowledge; it's about a change in the very nature of how we think. Madeline Levine, a psychologist and...