"My husband cheated on me because it's in his nature," or, "that woman stole because she was raised in a broken, abusive home." These sorts of attempts to explain or understand human behaviour are examples of the nature versus nurture debate. Proponents on both sides of this ongoing debate attempt to understand what causes people to think and act in certain ways.
Those who believe that nature is the cause of human behaviour often base their argument on genetics. They argue that behaviour is the result of inherited traits that people are born with. Despite experience and external circumstances, a person's fundamental nature and characteristics do not change. Thus, taken to an extreme, proponents of the "nature" side might argue that there is no such thing as free will because our destinies have already been determined by our traits. Thus, according to someone who believes nature determines behaviour, although a child may have had wonderful life experiences and a stellar upbringing, if he is genetically predisposed to violent behaviour, no amount of good parenting can alter that.
Supporters of the nurture side of the debate argue that environment is the main factor determining human behaviour. According to this theory, people are often beneficiaries or victims of outside circumstances: Children raised in healthy, positive environments are more likely to grow into productive successful adults than children raised in negative, threatening environments. Thus, people's behaviour is a reflection of how they were raised and the situations they experienced in life, not the result of inherited traits. A child could have been born with Einstein's IQ, but if she was raised in an environment that devalued intelligence, it's unlikely she would ever become a great scientist.
Studies that involve adoption or identical twins separated at birth are used as evidence in the debate. This is because these situations largely eliminate one factor or the other. In the case of adoption studies, scholars look at children who were born in one environment and raised in a completely different one. In twin studies, identical twins raised in different environments are examined. The adoption studies show a correlation between certain behaviours and genetics because the biological parents and children shared certain behaviours but not the same environment. Twin studies also show that genetics plays a strong factor in human development and behaviour. One study revealed a 50 per cent concordance between criminal behaviours in twins. However, this also leaves room for environmental factors to play a role.
Although people in non-scholarly debate may side passionately with either nature or nurture, most scholars believe that nature and nurture are both factors that shape human beings. Thus, the main argument isn't simply nature versus nurture, but what to what extent each factor affects individuals, and in what areas. Additionally, other factors such as culture, race and society play a role in shaping an individual. Ultimately, according to scholars, neither side has all the answers as to why people become who they are -- they both have some of the answers.