PassingPsych

Genetics is the study of patterns of inheritance of specific traits. An example of a gene is MAOA, which provides instructions for making an enzyme called monoamine oxidase A. This enzyme is part of a group of enzymes that break down chemicals called monoamines through a chemical reaction known as oxidation. Mutations in the MAOA gene can cause a deficiency in the enzyme monoamine oxidase A, leading to an increase in serotonin and other neurotransmitters in the brain. This condition, which only affects males, is characterised by mild intellectual disability and behavioural problems including aggressive and violent outbursts. In some cases, particular foods have been found to worsen the symptoms of the condition. In this essay, I will give a detailed account of the impact of genes on behaviours using the supporting study of Caspi et al.

Caspi et al aimed to investigate how environmental stressors might interact with our genetic makeup to result in aggressive behaviour. This interaction is called gene-environment interaction, which is the relationship between DNA and external stimuli that affect behaviour. To investigate, they used a quasi-experiment consisting of 1,037 male children who were born in 1972 in New Zealand. This longitudinal study examined the children for 26 years from birth to adulthood. They examined the genetic makeup of the children, concentrating on the MAOA gene. The upbringing of the children was also examined for any maltreatment. At the age of 26, the participants’ anti-social behaviour was measured. Results showed that men who had been maltreated and had high levels of MAOA activity were less likely to show anti-social behaviours as adults. Conversely, those who had been maltreated and had low MAOA activity were three times more likely to show anti-social behaviour.

Caspi et al demonstrate the effects of genes on behaviour. This is seen in participants with the low-activity variant of the MAOA gene (MAOA-L) who were maltreated, showing three times more anti-social behaviour. This is important as it shows that both the MAOA gene and the environment (in this case, maltreatment) affect behaviour. The low-activity variant of the MAOA gene decreases the production of the enzyme monoamine oxidase A, resulting in an increased amount of serotonin and therefore anti-social behaviour. Therefore, this study is useful in understanding the effects of genes on behaviour.