Aggression - role of genetic factors/genes

Question 1

Mason and Frick (twin studies)

Answer 1

• aggressive behaviour 50% due to genes
• used meta-analysis and measured variance
• twin studies criticized for shared environment, however also looked at adoption studies

Question 2

Coccaro (twin studies)

Answer 2

• 40% genetic

- assessed degree of genetic and environmental influences on aggression and measured concordance rates

Question 3

Hutchings and Mednick (adoption studies)

Answer 3

• positive correlation between number of convictions for criminal violence among biological parents and number of convictions for their adopted sons
• suggests genes have impact
• significant number of cases; 14000

Question 4

Button (gender differences)

Answer 4

• heritability of aggressive behaviour was significantly higher in females than males

Question 5

Brunner (role of MAOA gene)

Answer 5

• family with aggressive males
• all were suffering from genetic defect on X chromosome
• concluded that these men were suffering from a defective MAOA gene
• excess levels of neurotransmitters were not being broken down, found in urine samples

Question 6

Caspi (role of environment)

Answer 6

• childhood maltreatment
• boys who experienced abuse were at risk of developing into violent offenders
• increases risk of criminality by 50%
• no clear cause and effect relationship

Question 7

Caspi and Moffit (environment and gene)

Answer 7

• 1037 people
• found that severe maltreatment and mutant MAOA gene was linked to most antisocial behaviour
• no maltreatment and a mutant MAOA gene was linked to least amount of antisocial behaviour
• suggests antisocial behaviour is not a genetic disease, however genes and environment together increase risk of behaviour as just maltreatment alone did not have as much of a significant effect