Genetic Factors in Aggression

Question 1

What did Coccaro et al. find regarding aggression in twins?

Answer 1

50% concordance for MZ and 19% for DZ (physical aggression) and 28% (MZ) and 7% (DZ) (verbal aggression)

Question 2

Outline Hutchings et al’s study regarding adoption and aggression.

Answer 2

14,000 adoptions in Denmark - significant number of adopted boys with criminal convictions had biological parents with criminal convictions.

Question 3

Outline Rhee and Waldman’s study regarding genetics and aggression.

Answer 3

Meta-analysis - genetic influences could be found in 41% of cases of aggression observed.

Question 4

What is the function of the MAO-A gene?

Answer 4

Monoamine oxide is produced by the gene that breaks down serotonin after it has been expended and its chemicals are recycled to be used elsewhere.

Question 5

Differentiate between the two types of MAO-A gene.

Answer 5

MAO-A Low - leads to certain areas of inactivity in the brain - resulting in a build up of serotonin.

MAO-A High - overactivity in certain areas of the brain - leads to too little serotonin.

Question 6

Give some supporting evidence for the role of the MAO-A gene in aggression.

Answer 6

• Stuart et al. - 97 men who had physically abused their partners - those with the MAO-A Low variant were the most aggressive towards their partners.
• Frazzetto et al. - trauma, before the age of 15, triggered the MAO-A gene - diathesis stress model may be a more sensible suggestion to explain aggression.

Question 7

Give two advantages of the genetic explanations of aggression.

Answer 7

Advantages:
- Supporting evidence for involvement of genetics in aggression - Coccaro et al. - concordance 50% in MZ and 19% in DZ (physical aggression) and 28% and 7% (verbal aggression) - strong support for genetic bases though there must be another factor that influences - diathesis stress.

• Support for genetic basis from pro social studies - The high variant of the MAO-A gene must be associated with positive behaviour - Merlins et al. - males with the high activity variant were more co-operant in lab based tasks - real life applications - drugs may be used to reduce antisocial behaviour.

Question 8

Give two disadvantages of the genetic explanations of aggression.

Answer 8

Disadvantages:
- Methodology is inconsistent and various depending on the study - Rhee and Waldman - meta-analysis 51 studies - aggressive behaviour was largely due to genetic contributions though only when self-reports were used - thus making it highly difficult to draw veracious conclusions.

• Diathesis stress model may be more appropriate - Frazetto et al. - trauma before 15, triggered the MAO-A gene - reductionist explanation as it places emphasis on biology alone.