Genetic Factors

Question 1

What is MAOA (monoamine oxide A)

Answer 1

An enzyme that regulates metabolism of serotonin in the brain

Question 2

What is the MAOA gene

Answer 2

The gene responsible for the activity of the enzyme MAOA in the brain- the low-activity variant of the gene is closely associated with aggressive behaviour

Question 3

Outline a study which reveals the influence of the MAOA gene on aggression

Answer 3

Brunner et al. (1993) found that 28 males in a Dutch family, who had a history of impulsively aggressive behaviour (rape, attempted murder), had abnormally low levels of MAOA and the low-activity variant of the MAOA gene

Question 4

Describe an additional study which supports the role of the MAOA gene on aggression

Answer 4

Mertins et al. (2011) found that high-activity variant of MAOA gene can lead to less aggression

Question 5

If both twins share the same characteristic, what does this suggest?

Answer 5

-MZ = genetic influence (nature)
-DZ = environmental influence (nurture)

Question 6

Which twin study revelas the influence of genes on aggression

Answer 6

Coccaro et al. (1997) found concordance rates of physical assault were 50% for MZ twins and 19% for DZ twin and found concordance rates of verbal aggression were 28% for MZ and 7% for DZ twins

Question 7

Which adoption study reveals the influence of genes on aggression

Answer 7

Hutchings and Mednick et al. (1975) found that a significant number of adopted boys in Denmark with criminal convictions had biological parents with convictions for criminal violence

Question 8

Describe a study which has suggested that aggression is a result of a gene-environment interaction rather than just genes in isolation

Answer 8

Caspi et al. (2002) determined that children with low-activity variant of MAOA gene were more likely to show anti-social behaviour, only if they had been maltreated as a child

Question 9

Why is using different methods to measure aggression an issue

Answer 9

Makes it difficult to draw valid conclusions about the role of genetic factors if research findings vary depending upon how the aggression is measured

Question 10

Describe a study which suggests the influence of multiple genes on aggression and not just the MAOA gene

Answer 10

Stuart et al. (2014) found males who inflicted IPV were more likely to have the low-activity variant of the MAOA gene and the serotonin transporter gene (5-HTT)

Question 11

What do adoptions studies tell us about aggression

Answer 11

• if the same aggression trait is demonstrated by the adopted child and their biological parents= genetic influence (nature)
• if the same aggression trait is demonstrated by the adopted child and their adoptive parents= environmental influence )nurture)

Question 12

Explain the difference between the MAOA-L and MAOA-H variants

Answer 12

• people with the MAOA-L variant produce less of the MAO-A enzyme
• people with the MAOA-H variant produce more of the MAO-A enzyme