Brunner et al,. (1993) – Genes and Serotonin

Brunner et al,. (1993) – ‘Abnormal behaviour associated with a point mutation in the structural gene for monamine oxidase A,’ Science 262 (S133), 578-80.




This is the second study we look at from the ‘Biology’ section of ‘Turning to Crime’. As part of your OCR A2 Psychology Exam. It is further categorised into ‘Genes and Serotonin.’

How much do genes and neurotransmitters contribute to the development of criminal behaviour? As this study is from the biological section, you may not be surprised to find out that genes and serotonin are central to the study. “Studies of aggressive behaviour in animals and humans have implicated altered metabolism of serotonin, and to a lesser extent dopamine, and noradrenaline [also known as norepinephrine] . These observations suggest that genetic defects in the metabolism of these neurotransmitters may affect aggressive behaviour, but such mutations have not yet been reported.” (1). Brunner lists a myriad of sources for the above quotation, however the background research we will be focusing on will be:

  • Osborn and West (1979)
  • Bohman (1955)
  • Price (1966)
  • Witkin (1976)

Osborn and West (1979)

Osborn and West studied the sons of criminals in order to discover if it is possible to inherit criminal tendencies. The results showed that only 13% of the sons of the non-criminal fathers in the study had convictions. Whereas, 40% of the sons of the criminals.

Bohman (1955)

Bohman studied both the adoptive and biological parents of children. In order to understand if biology had a greater impact upon behaviour or if nurture did. 40% of the children who had biological and adoptive parents with criminal records, had convictions. However only 12% did if the biological parents had criminal records and the adoptive parents didn’t.

Bohman concluded that the highest risk of a child developing criminal traits is present when genetic and environmental factors are present. Bohman also concluded that there is a greater chance of children becoming criminals if their parents have criminal records.

Price (1966)

Price found that chromosome abnormalities can cause changes in behaviour.

The male chromosome is XY and the female chromosome is XX. However Price found an abnormality wherein the male chromosome becomes XYY—which is otherwise known as “The Super Male Gene”—Price studied Scottish state hospitals for the criminally insane.

Price found that 28% of the men in the hospitals had the XYY defective gene, as compared with under 0.1% of the normal population.

Witkin (1976)

Followed on from Price’s research concluded that the men who are afflicted with this disorder are more likely than the general population to be involved in crime.

Witkin offers both a genetic explanation and a social explanation: Witkin suggests that the genetic impairment may cause characteristics like low intelligence and above average height, which in turn are viewed negatively by other people and thus lead to the afflicted individual developing criminal traits.


The research aimed to study and understand the behaviour of the males in a large family in the Netherlands. The behaviour exhibited by the males in the family was borderline mental retardation (their average IQ was around 85), and violent behaviour. Examples of the behaviour include:

  • Attempted rape
  • Exhibitionism
  • Arson
  • Impulsive Aggression


As the males had a hereditary genetic disorder, Brunner couldn’t have manipulated the independent variable.



5 Males from the family in the Netherlands, all of whom have the same genetic condition, which was later called Brunner Syndrome.

Two carrier females and one non-carrier females were used as a control and compared with 3 clinically affected males.

Females are not affected by the condition, although they can carry the condition in their genes, but they do not exhibit any symptoms.


All the males acted aggressively when angry, fearful, or frustrated.

A base change in the DNA structure was identified in all 5 males. This in turn resulted in flawed monoamine metabolism, which is linked with a deficit of the enzyme monoamine oxidase A (MAOA). The reason only males are affected is because it is specifically the single X chromosome which is responsible for the production of MAOA.

It is important to note that not all the males in the family were afflicted with the inability to control their aggression, even if they suffered mental retardation.


Brunner concluded that it is likely that the defect in the gene which causes flawed serotonin metabolism is the cause of the mental retardation and thus the aggressive behaviour exhibited in the males. The MAOA deficiency accounts for their inability to regulate their aggression.


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This is a very rare condition, which both accounts for the small sample and the lack of generalisability. This study provides support for the determinism argument as the men in the study all had a genetic condition which was not learned, their behaviour will always be predetermined by their condition. Of course the study is androcentric as the condition is only experienced by males, but it is also ethnocentric for no good reason apart from the rareness of the condition.

It could be argued that this study is reductionist as there is a complete lack of other variables studied, given that there were males who did not exhibit aggressive behaviour, the conclusions of the study could be questioned.

As the methodology of the study was scientific there is no social desirability bias.

  1. Brunner et al,. (1993) – ‘Abnormal behaviour associated with a point mutation in the structural gene for monamine oxidase A,’ Science 262 (S133), 578-80.
Further Reading

The Private Life of the Brain (Penguin Press Science)


Brunner et al,. (1993) - Genes and Serotonin
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Brunner et al,. (1993) - Genes and Serotonin
Brunner et al,. (1993) is one of the studies you need for your A2 OCR Psychology studies. It considers genetic explanations of criminal behaviour.