To what extent to physiological factors explain why people become criminals?

In this essay the extent to which physiological factors influence peoples behaviour, and primarily whether or not they will become criminals, will be discussed. This area is greatly influential within the nature/nurture debate, which is a core debate in psychology, as it looks at whether behaviour is influenced by genetics more than by the environment or whether it is the other way around. This essay will look at what effect different genetic influences can do to a person.

It is also important to point out that the discussion will focus on physiological (or biological) factors of the body and not at mental aspects of the brain. It will look at issues including inherited characteristics and twins. The first item that would be looked at when discussing physiological factors is a persons genetic factors. The first person to look at why criminals are criminals was Lambroso (1876) and he thought the origins of criminality were gene based. Schafer (1976) credited Lombroso as the father of criminality as he was the first person to really look into the reasons for being a criminal.

He thought that certain criminals could be identified by body shape and facial characteristics, for instance he thought that all sex offenders had big lips and protruding ears. He originally suggested that criminals were "born not made". He was however criticised for his methods. Lambroso only looked at convicted criminals already in prison during his research but never made comparisons with non-criminals or even non-convicted criminals, so he had no control group to back up his findings against.

It has also been suggested that he confused criminality (the study of criminals) with psychopathology (the study of people with severe mental disorders, who commit violent crimes). He has however also been praised with the fact that he started people looking into the reasons of why people become criminals at all. Another type of study into whether genetic influences can cause criminality is family studies. These look at certain families to see if crime runs through the family. Osborn and West (1979) studied fathers and sons to look for a link.

Criminal fathers and non-criminal fathers were compared and their sons were also followed to find out if they would commit crimes. They found out that 40% of the sons of criminal fathers became criminals as well compared with 13% of the sons of non-criminal fathers. There have been several family studies undertaken but they are criticised – it is argued that although children share 50% of their genes with their fathers they are also likely to share a very similar upbringing in a similar environment.

So, whether they are or aren't criminals cannot be said, from the findings of family studies, to be due to nature or nurture alone. A study along the same lines as family studies is Adoption studies. These follow adopted children who don't grow up in the same environment as their natural parents, who either are or aren't criminals. If there is a correlation between parents and children it is more likely to be down to genetics rather than environment. A reliable study in this area is one done by Mednick et al (1983) who studied 14,500 adopted children.

He found that a boy with a biological parent as a criminal was much more likely to commit a crime than a boy with a non-criminal parent. Crowe (1974) found that an adopted boy with a criminal as a biological mother had a 50% chance of committing a crime whilst a boy with a non-criminal mother had a 5% chance. Other studies, however, have found that if an adopted boy's adopting father is a criminal as well as his biological father then he is more likely to become a criminal as well, so environment can be shown to play a part even here.