Aggression: Genetic Influences

Question 1

Tests for genetic influence

Answer 1

Twin studies
adoption studies
epigenetics

Question 2

Concordance rate

Answer 2

The probability a pair of individuals will both have a characteristic, given that one pair has the characteristic

Question 3

What type of twin should concordance rates be higher in

Answer 3

Monozygotic as they share 100% of their genes

Question 4

Twin studies

Answer 4

Similarity in aggressive tendencies should be higher in MZ twins than DZ twins because both sets of twins share the same environment.
However:
MZ share 100% of genes
DZ share 50% of genes

therefore any difference in concordance rate should be down to genes

Question 5

McGuffin (1985)

Answer 5

Twin studies
Found MZ twins concordance rate for aggression 0.8 7
Found DZ twins concordance rate for aggression 0.72

Question 6

Coracco (1997)

Answer 6

Twin studies
Found 50% of aggressive behaviour towards others is due to genetics
suggests a genetic underpinning
50% is high when considering other factors like deindividuation, Social learning, and institutional agg.
These may have an impact but much smaller in comparison to genetic influence

Question 7

Adoption studies

Answer 7

Can I help determine the relative contributions of environments and hereditary aggression

Question 8

How are adoption studies carried out?

Answer 8

Compare rates of aggression of adoptees with their biological parents. If strong concordance rate, suggests didn’t learn aggression through environment must have a genetic base

Question 9

Hutchings and Mednick. Procedure

Answer 9

Adoption studies

Conducted large-scale adoption study Denmark 14,000 adoptees

Question 10

Hutchings and Mednick. Findings

Answer 10

Adopted boys with criminal convictions in Denmark found to have biological parents mainly fathers with criminal convictions.
Supports genes are the cause of aggression rather than environment

Question 11

Epigenetics

Answer 11

Changes in organisms, caused by modification of gene expression

Question 12

MAOA gene in humans

Answer 12

humans have various forms of the MAOA gene, resulting in different levels of activity of the enzyme

Question 13

What does MAOA do?

Answer 13

an enzyme

breaks down important neurotransmitters in the brain, including dopamine and serotonin;

Question 14

Brunner et al 1993

Answer 14

MAOA gene
Dutch family - males were violent, aggressive criminals
Found the same genetic mutation which affected production of MAOA (has abnormally low levels of MAOA)
Therefore not producing enough serotonin leads to aggression

Question 15

Brunner - criticism

Answer 15

One case study
Idiographic
Not generalisable

Question 16

Caspi 2002

Answer 16

MAOA gene
Studies 500 male children and identified two variants of MAOA gene:
MAOA-H
MAOA-L

Question 17

MAOA-H

Answer 17

High levels of MAOA = low levels of aggression

Question 18

MAOA-L

Answer 18

Warrior gene
Low levels of MAOA, high levels of aggression BUT

nature-nurture interaction: Found children with warrior gene only became aggressive if they’d been maltreated as a child - Caspi

Question 19

Conclusion

Answer 19

Born with a predisposition for aggression, but environmental factors trigger it
diathesis stress model

Question 20

RWA x Ethics

Answer 20

Suggest people’s genes predisposition towards aggressive behaviour
Genetic engineering used to change genes and reduce risk
More extreme = chemical castration
Labelling individuals as dangerous based on genetic inheritance poses serious ethical questions

Question 21

Twin studies criticism

Answer 21

Theory that MZ twins share and environment to the same extent as DZ twins do, not necessarily true
MZ twins = more likely to be treated identically
DZ twins = more independent and gain individual identity

Question 22

MAOA is regulated by

Answer 22

the MAOA gene