Small children live in a world that’s difficult for them to manage and in which they often stand accused of doing damage of one kind or another. Denying wrongdoing is therefore their most usual kind of lie and the kind that most often gets them into trouble. Your child breaks his sister’s doll by mistake. Faced with it, he denies the whole incident. Your are probably angrier with him for the lie than you are about the breakage.
If you feel strongly that your child should own up when he has done something wrong, do make it easy. “This doll is broken. I wonder what happened?” is much more likely to enable him to say, “I broke it, I’m sorry” than “You’ve broken this doll, haven’t you, you naughty, careless boy.” But if your child does admit to something, of his accord or because you force it out of him, do make sure that you don’t overwhelm him with anger and punishments. You cannot have it both ways. If you want him to tell you when he has done something wrong, you cannot also be furious with him.
Many young children – especially those with no older brothers and sisters to keep asserting “That’s mine!” – are as vague about property rights as they are about truth. Within the family there will be lots of things that belong to everybody, some that belong to particular people but can be freely borrowed and a few that are “private possessions” for the use of the owner only. Outside the family there are complications too. It is all right to keep the little ball you found in the bushes in the park but it is not all right to keep a purse. It is all right to bring your painting home from nursery school but not a piece of play dough. People are allowed to take flyers from stores (though not the whole pile) but not packages of soup (not even one). There’s no purpose in making a moral issue out of young child’s collecting things that catch his fancy until he’s able to understand all this. You cannot afford to take it entirely casually, though, because even at the age of three or four, other people may call it stealing and make a major song and dance about it.