In a healthy family surrounding they probably haven't been traumatized by the ills of the social world, learned to be afraid of climbing high into a tree, eating bugs in the yard (hey, Mom and Dad buy bugs to eat at the market, so why not?) and the many other lessons most of us learn along the way.
They see someone smiling at them, and they smile back. It's wonderful. The girl tending the family BBQ banana stand in a night market, the boy playing in the pipe at a playground, the two girls on the bench and the impish smile of our self-appointed tour guide at Erawan cave (with the unfortunate teeth he tried to hide) - these are all memories I look back on fondly.