Teenagers are trying to be different than their parents

Psychology researcher Judith Rich Harris formulated the theory that children's personalities are mostly influenced by their genes and their social group. The theory contradicts the myth that the way the parents raise their children has the most important role in the shaping of their character. According to her research the teenagers personality is formed when they are trying to fit in with the group or to compete with their peers.
There is an article on edge.org about the work of Judith Rich Harris: link