It’s a common sight on Japanese mass transit: Children troop through train cars, singly or in small groups, looking for seats.

They wear knee socks, polished patent-leather shoes, and plaid jumpers, with wide-brimmed hats fastened under the chin and train passes pinned to their backpacks. The kids are as young as 6 or 7, on their way to and from school, and there is nary a guardian in sight.

Even in big cities like Tokyo, small children take the subway and run errands by themselves. The reason has a lot to do with group dynamics. —Atlantic