I can understand that, when my Dad had a kid with my step mum even when she was very young, not even old enough to speak decently, if she did something wrong her face would show it. You just looked at her and knew she'd done something. I can't remember what it was, something to do with the hamster I think, but she'd never done it before and never been told off for anything like it but she knew she id something wrong. It's inbuilt.
Children are very perceptive, they pick up how to talk for a start, telling when they're about to get a ******ing is easy by comparison.