Genetic factors in aggression Flashcards
What is MAO-A (monoamine oxidase A)?
An enzyme that regulates the metabolism of serotonin in the brain
What is the MAOA gene?
The gene responsible for the activity of the MAOA enzyme in the brain. The low-activity variant is closely associated with aggressive behaviour
What study reveals the influence of the MAOA gene on aggression?
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;s of MAOA and the low activity variant version of the MAOA gene
What is the difference between monozygotic and dizygotic twins?
Monozygotic twins 100% of their genes,
Dizygotic twins share 50% of their genes
Which twins study reveals the influence of genes on aggression?
Coccaro et al. (1997)- found physical assault concordance rates of
MZ- 50%
DZ- 19%
and verbal aggression concordance creates of
MZ- 28%
DZ-7%
Which adoption study reveals the influence of genes in aggression?
Hutchings and Mednick (1975) found a significant number of adopted boys in Denmark with criminal convictions had biological parents with convictions for criminal violence
What is the strength of genetic factors in aggression?
Reseach support for MAOA gene- Brunner et al. (1993) showed that the low-activity varient of the MAOA gene is associated with aggression.
Mertins et al. (2011) found the converse isi true and that high activity varient of the MAOA gene is associated with less aggressive behaviour. In a money disributing game they found thta males with the high-activity varient were more co-operative and made fewer aggressive moves than the low- activity varient.
Counter- The study also showed that non-genetic factos play a role. Even ptpts with the low activity gene behaved co-operativly when made aware that other ptpts were. Knowledge of a social norm partly determined how aggressive or co-operative the MAOA-L ptpts were.
What are the 3 limitations for genetic factors in aggression?
Diathesis-stress model- An individual may possess a gene associated with aggression, but that behaviour is only expressed if the environmental conditions are favourable. Caspi et al. studied 500 male children and found that those with the MAOA-L gene were significantly more likely to grow up to exhibit anti-social behaviour but only if they were maltreated as a child. Children with the MAOA- H who were maltreated gene and those with the MAOA-L gene that were not maltreated did not display the same anti-social behaviour.
Problems with measuring aggression- Studies investigating aggression differ massively in terms of the method they use. E.G self reports, direct observations, teacher reports. Rhee and Walden (2002) carried out a meta analysis of adoption studies investigating the genetic influence of aggression and found generate factors had a greater influence on aggression studies using self-reports than parents/teacher. Difficult to draw valid conclusions.
Problems with twin studies- Twin studies may lack validity. In every pair of twins we assume they hair the same environment as each other as they are raised together (equal environments assumption) however DZ twins may not share their environment to the same extent as MZ twins. MZ twin are treated very similarly by people especially parents (praising them equally to be aggressive) but this may not be the case with DZ twins. This means that concordance rates are inflated.
