Genetic Factors In Aggression

Question 1

Outline- twin studies Coccaro et al (1997)

Answer 1

Coccaro et al (1997)

• concordance of aggression between MZ and DZ twins
• behaviour defined as direct physical assault, the researcher found concordance rates of 50% for MZ twins and 19% DZ twins
• verbal aggression concordance of 28% MZ and 7% DZ.

Question 2

Outline- MAOA gene

Answer 2

The gene responsible for the activity of the enzyme monomine oxidase in the brain. Low activity of the gene is closely associated with aggressive behaviour.

Question 3

Outline- Gene-environment interactions study

Answer 3

Giovanni frazetto et al (2007)
-found association between agression and low level activity from MAOA gene, but only if the patient had experience significant trauma during the first 15 years of life.

Question 4

Evaluation- support for MAOA

Answer 4

Mertins et al (2011)
-studies those with low activity MAOA and high activity
-they had to make decisions as to whether or not they should give money for the good of a group in a situation
Results- found males with high activity MAOA were less aggressive and more co-operative
Than the low activity group.
So- MAOA low activity does cause aggression

Question 5

Evaluation- non human animal studies.

Answer 5

Godar et al

• it’s possible to ‘knockout’ (remove) genes from animals
• mice who had their MAOA knockout showed significantly increased serotonin levels in the brain and were hyperaggressive.
• shows how high MAOA activity is needed to mop up serotonin to reduce aggression

Question 6

Outline- adoption studies

Answer 6

Rhee and Waldman (2002)

• meta analysis of adoption studies of direct aggression and anti social behaviour.
• they found genetic influences account for 41% of the variance in aggression.
• similar to twin studies.