Genetic factors in agression Flashcards
Twin studies
(Coccaro et al. 1997)
AO1
A study using adult twin pairs found that nearly 50% of the variance in direct aggressive behaviour (i.e agression towards others) could be attributed to genetic factors (Coccaro et al. 1997)
Adoption studies
(Hutchings and Mendnick, 1975)
AO1
A study over 14,000 adoptions found that a significant number of adopted boys with criminal convictions had biological parents with convictiions for criminal violence.
Research on genetic factors in agression
Miles and Carey, 1997
AO1
A meta-analysis of twin and adoption studies found a strange genetic influence in aggression. Both genes and family enviroment were influential in determing aggression in youth, but at later ages the influential in determining aggression in youth, but at later ages the influence of rearing enviroment decreased and the influence of genes increased
Rhee and Waldman (2002)
AO1
Concluded that although aggressive anti-social behaviour was largely a product of gentic contributions, the influence of other factors affected their expression.
MAOA: A gene for aggression?
A gene responsibility for produing the enzyme MAOA is associated with aggressive behaviour. MAOA regulates the metabolism or serotonin the brain, and low levels of serotonin are associated with implusive and aggressive behaviour.
Capsi et al. (2002)
Discovered a variant of the gene associated with low levels of MAOA (MAOA-L). Those with this variant were significantly moe likely to grow up to exhbit anti-social behaviour but only if they had been maltreated as children. Children with the MAOA-L variant who were not maltreated or not display anti-social behaviour.
AO3
Problems of sampling
P: It is difficult to draw meaningful conclusions from studies that have focused exclusively on individuals convicted of violent crime.
E: Convicitons for violent crime relatively few compared to the vast number of violent attacks by individuals that never result in a conviction. They therefore represent just a small minority of those regulary involved aggressive behaviour.
E: This might explain why so many studies have found little or no evidence of heritability for violence.
Difficulties of determining the role of genetic factors
P: It is difficult to establish genetic contributions to aggressive behaviour for the following reasons:
E: As well as genetic factors, there are many non-genetic (i.e enviromental) influences on the manifestion of aggresive behaviour. These influences may interact with each other. Genetic factors may affect which enviromental factors have an influence and vice versa (gene-enviroment interaction).
E: This highlights the problem of identify the specific contributions of genetic factors to aggresive behaviour.
Evidence for the influence of the MAOA gene
P: A Finish study has added research to support that the MAOA gene is implicated in severse violent behaviours.
E: Tilhonen et al. (2015) studies prisioners revealing that the MAOA-L variant, in combination with another gene (CDH13), was associated with extermely violent behaviour. There was no substiantial evidence for either of these genes among non-violent offenders, indicating this combination of genes was specific for violent offending only.
E: However, although these genes may make it harder for some people control violent urges, they do not predetermine violent behaviour.
The MAOA gene might explain gender differences in aggressive behaviour
P: An advantage of MAOA gene research is that it offers an explanation that for the uneven rates of violence males and females.
E: Niechoff (2014) this is a consequence of the differential genetic vulnerabilty that males and female have to the MAOA gene. The MAOA gene is linked to the X chromosomes. Women have two X chromosomes, whereas men have only one and are therefore more likely to be affected.
E: This could explain why males typically show more aggressive behaviour than females.
What 4 AO3 are you using?
Problems sampling
Difficulties of determing the role of genetic factors
Evidence for the influence of the MAOA gene
The MAOA gene might explain gender differences in aggressive behaviour.
