Children's developing understanding of social norms

Although children are influenced by social norms from birth, they only begin to understand social norms as such in the three to five year age period. It is at this age that they begin to enforce conformity to social norms on others, even using the normative language of should, must, and ought to. By the end of this age period, they are even capable of creating new social norms (i.e., game rules) themselves, and they automatically see these as binding on everyone concerned, suggesting an understanding that the force of social norms comes not just from adult authority but also from agreement. Although particular social norms differ among cultures, it seems that children in all cultures are born with the same basic norm psychology.