There was a time when “playing with friends” didn’t require checking three family calendars, texting four parents, figuring out who was driving, and setting a pickup time. You just went outside. Maybe you knocked on a neighbor’s door. Maybe you rode your bike around until you found someone. Maybe you ended up sitting on a curb with a bunch of kids doing something random, which somehow, was still fun. I recently wrote about wanting my daughter to have a ‘90s childhood, and this concept that Jonathan Haidt recently spoke about has that vibe. The social psychologist and author of The...