theories of crime

  • Created by: jayeca
  • Created on: 25-02-21 09:34

XYY Syndrome

Some chromosome abnormalities feature extra chromosomes, such as XYY – which means a person has an extra Y chromosome. Blood samples can be taken from criminals to see if they have chromosomal abnormalities that might cause their criminal behaviour.

  • XYY men are sometimes known as ‘super males’. Criminologists are interested in this syndrome as it is believed that men with XYY syndrome are more aggressive and more likely to be violent and criminals than males with a single Y chromosome.
  • This condition is not inherited, so it does not run in families, even though it may be a genetic reason for criminality.
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XYY Syndrome Research

  • Jacob et al. (1965) suggested than men with XYY syndrome were more aggressive than XY men. Some studies have found that there are more XYY men in the prison population.
  • XYY – 15 per 1000 in the prison population compared to 1 per 1000 in the general population. This means that XYY men are over-represented in the prison population.

Case study 

  • John Wayne Gacy (who sexually assaulted, tortured and killed at least 33 men in the USA is said to have XYY syndrome.

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Strengths of XYY

  • Supporting research
  • Adler 2007: indicated that it is possible that aggressive and violent behaviour is at least partly determined by genetic factors
  • Jacob 1965: Found a significant number of men had XYY gene in prison
  • Shows a reason for higher levels of aggression- explanatory power
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Weaknesses of XYY

  • Studies have shown abnormalities are widespread over the general population and therefore do not explain aggression
  • Too much focus on genetics, ignores behaviorist approach.
  • Theilgaard 1984: compared traits between XY and XYY men and found that aggression was not associated with XYY men
  • Doesn’t explain women criminality
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Twin Studies

Twin studies support the idea that a heritable trait may increase the risk of criminal behaviour.

Monozygotic or MZ twins share 100% of their DNA.

Dyzygotic or DZ share 50% of their DNA.

If both twins share a characteristic there is said to be a concordance rate.

In order to determine the role of genetic and environmental influences, (or nature versus nurture) many twin studies have taken place.

Evidence has been found that suggests genetics or nature plays a role in criminality to the extent that concordance in MZ twins is greater than in DZ twins.

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Twin Studies Research

Lange (1929) found that MZ twins showed a higher degree of concordance than DZ twins for criminal behaviour. 10 of the 13 MZ twins had both served time in prison, whereas only 2 of the 17 DZ twins showed concordance.

Christiansen (1977) studied a larger sample of 3,586 twin pairs from the Danish islands and found concordance rates of 35% (MZ) and 13% (DZ) for male twins. And 21% (MZ) and 8% (DZ) for female twins.

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Strengths of Twin Studies

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Weaknesses of Twin Studies

Early studies, such as Lange 1929, lacked accurate control groups. Unsure whether MZ or DZ, guess work!

Small samples in many twin studies, not generalisable.

If twins are brought up in the same environment, criminality could just be as easily related to nurture rather than genetics.

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Adoption studies

We can use adoption studies to explain criminal behaviour by comparing criminals with their biological and adoptive parents. 

Studies like this look at the impact of nurture on children who are raised by their non-biological parents.

If, in criminal behaviour the child is more similar to their biological parents than their adoptive parents, (who they share the same environment with) a genetic (nature) basis of criminality can be suggested.

BUT: if a child is more similar to their adoptive parents, we could argue an environmental (nurture) cause for criminality. 

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Adoption studies Research

Hutchings & Mednick (1975) studied 14,000 adopted children and found a high number of boys with criminal convictions had biological parents with criminal convictions too. This suggests a link between aggression and genetics.


Mednick et al (1994) found no relationship between the number of criminal convictions of adoptive parents and their adopted children. They DID find a correlation (relationship) between the number of criminal convictions of biological parents and their offspring.

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Strengths of Adoption studies

Adopted children are exposed to a different environment than their biological parents, easy to separate genetic and nature factors.

Crowe 1972: 50% of children with criminal biological mothers because criminal by 18, whereas only 5% of children without a criminal mother became criminal by 18.

Bohmen et al 1982: When the biological father was an alcoholic and committed violent crimes, the biological son tended to as well.

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Weaknesses of Adoption studies

The age of adoption may mean the adopted child has already been influenced by their natural parents or foster environment.

Information about biological family is not always available, so comparison cannot always be made.

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Cesare Lombroso

Lombroso said:

A criminal is a ‘separate species’

Lombroso argued that criminals were born, not made (supports the nature argument)

Lombroso said that offenders possess similar characteristic to lower primates and this could explain their criminality

He argued that a ‘born criminal’ could be determined by the physical shape of the head and facial features

Criminality is heritable and criminals had ‘atavistic (or primitive) features’

These features are ‘throwbacks’ to an earlier stage of human development

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Atavistic Features

Atavistic Features include:

•Large or forward projecting jaw

•High cheekbones

•Flattened or upturned nose

•Low, sloping forehead 

•Long arms in relation to lower limbs

•Large ears

A male with five or more of these physical anomalies is marked as a born criminal.

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Lombroso Theory Research

A recent study from a university found that facial features can identify a criminal.

ID photographs of 1,856 Chinese men (50% had a previous conviction) were entered into an artificial intelligence programme.

It wrongly flagged innocent men as criminal 6% of the time BUT correctly identified 83% of real criminals.

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William Sheldon

•Sheldon (1949) developed a theory that shares Lombroso’s idea that criminal behaviour is linked to a person’s physical form.

•Sheldon’s findings were produced in his book Atlas of Men in 1954.

•He carefully examined photographs showing the front, side and back of 4,000 men wearing few clothes.

•Sheldon proposed that there are 3 body types or ‘somatypes’

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Brain Abnormalities

Several research studies have suggested that damage to the pre-frontal cortex of the brain may cause altered behaviour in individuals.

Behaviour changes include:

•Immature behaviour

•Loss of self-control

•Struggling to modify behaviour

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Brain Abnormalities Research

Raine et al (1994) used PET scans to study the living brains of impulsive killers. He found damage in the pre-frontal cortex of the brains of criminals – the part of the brain which controls impulsive behaviour.

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Case Study: Phineas Gage

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Brain Abnormalities Modern Research

Recent research in Canada (Mc Isaac et al., 2016) found that people who have had serious head injuries are twice as likely to go to prison. Female prisoners were even more likely to have survived brain injury. The risk of women who had suffered brain injuries was 2.76 higher than for uninjured women.

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Aspects of a person’s diet such as low blood sugar (hypoglycaemia associated with diabetes), additives in food, and, pollution can influence the chemistry of the brain.

Research has found that low levels of serotonin (a neurotransmitter/chemical in the brain that is thought to regulate mood) 

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Scerbo & Raine (1993) carried out a meta-analysis of 29 studies looking at

antisocial adults and children. They found low levels of serotonin in all studies.

•It is possible to control serotonin levels by diet.

•The following foods can help raise serotonin levels: 

Salmon, Poultry, Eggs, Spinach ,Seeds ,Milk ,Soy products, Nuts 

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People who take steroids in large amounts can become very violent. This is known as ‘roid rage’

Steroids are usually taken to increase muscle growth, but they also increase testosterone levels. (Testosterone is a hormone thought to be implicated in aggression).

Horace Williams was an American body builder who killed a man by beating him after taking 2,000 times the recommended dose of steroids.

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