More recently the discussion into what the most likely cause of crime is has changed. From the 40's and onwards psychologists such as Sheldon and Lambroso have tried to prove the cause of crime as being genetic and down to the nature of the person committing them. Lambroso himself suggested that "Criminals are born not made" and tried to conduct research to prove this.
However, whilst it is highly recognised that there is a general biological difference between those who commit common crimes and the 'average citizen', more recent research has examined closely the effect that outside causes have on people turning to crime. The discussion on criminality has changed from whether the 'Nature' side of a person is to blame for it or whether the 'Nurture' received by people is the primary reason. Since the 'Nature' of criminals has been looked at and respected conclusions have been drawn, more psychologists have been looking into how 'Nurture' has led to criminality.
One aspect that the 'Nurture' side of studies looks into is the social influences that people are receiving at this point in history. In the time of Sheldon and others people only socialised within their town. Since towns used to be much smaller, this used to only give them access to people within a radius of about 2 miles. But, now that there is improved travel, schooling and places of work, people socialise with a group that can range to a radius of about 25 miles. Also, with improved communication, people can speak to others who are almost anywhere on the planet.
Another aspect of whether it is the 'Nurture' a person receives that leads to their criminality is the current widespread effect of the media. People, it has been shown, can be influenced by what they see and hear on television (TV) and the radio. They can also be taught aggressive behaviour through violent video games, and people can access information on almost any subject, including criminality, on the Internet.
This new, wider range of influences is continually being studied to find the effect that it can have on people. There are many social factors that affect how a person develops. Social learning theory suggests that much of what we learn is done by imitation and modelling others behaviour. Therefore the influence of other people on us is a major factor in shaping our behaviour.
It is also important to point out that there are different types of aggression, including anti-social aggression – which encompasses behaviour that intends to harm someone, physically or psychologically, who doesn't want to be treated as such; pro-social behaviour – such as when a policeman shoots a criminal to protect people; and sanctioned aggression – such as self-defence, for example when someone causes harm to their attacker.
One influence on all types of behaviour is the self-fulfilling prophecy – which suggests that people tend to be become what is expected of them – and this can be used to explain why people turn to crime. Labelling theory ties in here as well, since it says that someone only becomes a criminal when labelled a criminal by society. It is not what the person does that matters, but how society labels what they do, because people can end up becoming their label.
Rosenthal and Jacobson (1968) carried out one of the most well known studies into the self-fulfilling prophecy. First of all they gave students in a class an IQ test, but they selected students at random, irrespective of their IQ results. They told their teacher that they were about to 'spurt' and when they tested them at the end of the year they found that those "identified" had all improved.
Because the teachers had expected them to improve they had given them more attention and help so that the 'prophecy' came true. A study by Eden (1990) used a similar method with 29 platoons of soldiers. Some platoons were told that they were above average whilst the other platoons were told nothing, though all of the platoons were at an average level.
After ten weeks the soldiers' performance was tested and the groups in the 'informed' platoons were found to have achieved best on both written and weapons tests. However, the self-fulfilling prophecy can work in both positive and negative ways and whilst it can be shown to help some people it can also be used as an explanation of why people would turn to crime. Social expectations, especially if people live in a criminally minded group or have low self-esteem, may encourage people to become criminals. On the other hand, it can be a positive influence if people have high expectations for others.