One very thorough study of “children’s independent mobility,” conducted in urban, suburban, and rural neighborhoods in the U.K., shows that in 1971, 80 percent of third-graders walked to school alone. By 1990, that measure had dropped to 9 percent, and now it’s even lower. When you ask parents why they are more protective than their parents were, they might answer that the world is more dangerous than it was when they were growing up. But this isn’t true, or at least not in the way that we think. For example, parents now routinely tell their children never to talk to strangers, even though all available evidence suggests that children have about the same (very slim) chance of being abducted by a stranger as they did a generation ago. Maybe the real question is, how did these fears come to have such a hold over us? And what have our children lost—and gained—as we’ve succumbed to them?