The minds of children are almost never at rest. Sometimes you can literally see the gears moving in their little brains! Their minds are constantly in motion. Have you ever watched a preschooler sleep during nap time? If not, I highly recocommend it! You can see their little eyes dancing as they dream. It's amazing.
Recently a man came into my office while I was talking to one of our 3 year olds. She didn't know him and was very reserved.