The nature-nurture debate is all about whether or not our behaviour stems from our genes or whether the environment around us and the way we are raised is the reason for why we behave in certain ways. Nature is what we are born with, the characteristics we inherit from our parents and things that cannot be changed. Nurture is what we learn from the things around us and the environment we are raised and live in.
When looking at nature, this side of the debate suggests that everything we are and everything we will become is determined by our genes and our biological make up. The way we are does not necessarily happen from birth as certain genes can change as the body matures and so, as a person gets older, certain characteristics that they have inherited may begin to show.
Aggression is one of the things which researchers are debating about; is it due to nature or nurture?
Twin studies are very useful in this area because monozygotic (MZ) twins, who share 100% of their DNA, will prove whether or not aggression (or any other behaviour for that matter) is due to the genes we inherit. If the aggressiveness between MZ twins is more similar, this is considered to be down to the role of genes; for example, Coccaro et al found that nearly 50% of the alteration in aggressive behaviour towards others could be accredited to genetic factors when he studied behaviour in adult twin pairs.
Adoption studies are also useful because they can compare genes of biological parents to the environment around the adopted parents to see which is the cause of aggressive behaviour. If there is a correlation between an aggressive individual who has been adopted yet has aggressive biological parents, then the behaviour is said to be down to the genes, and vice versa. Mednick studies 14,000 adoptions and found that there was a positive correlation between boys who had criminal convictions and their biological parents who had criminal convictions (particularly