From the time that a boy and a girl are born their role is already given to them genetically. A boy knows how to behave like a boy and girl knows how to behave like a girl. Parents only teach the children a role that is accepted in society. Children learn from Mommy takes care of the children and comb her daughter's hair and daddy may fix a broken lock or change the oil in the car. When a girl is given a doll she automatically knows what to do with it by watching her mother comb her own hair, but this doesn't define a girl as being a girl, its all genetic, the girl and boy's natural instincts would develop.
Second Answereer says: I would think that they define their character that way, yes!