Aggression: Genetic Factors in Aggression Flashcards
Describe the role of Twin Studies in Genetic Factors in Aggression
The role of genetic factors in aggression can be tested in twin studies. Genes are identical in sets of monozygotic twins but are different between sets of dizygotic twins, meaning that if monozygotic twins are more alike in terms of aggression than dizygotic twins are, this similarity can be attributed to genetics. Coccaro et al. performed a twin study, and found generally that almost 50% of variance in aggressive behaviour can be attributed to genetic factors.
Describe the role of Adoption Studies in Genetic Factors in Aggression
Adoption studies can help determine the relative contributions of environment and heredity in aggression. Positive correlation between adopted children and their biological parents implies a genetic effect, while positive correlation between the child and their adoptive parents implies an environmental effect. A study of over 14,000 adoptions in Denmark by Hutchings and Mednick, found that a significant number of adopted boys with criminal convictions had biological fathers with criminal convictions, demonstrating a genetic effect.
Which gene has been potentially linked to Aggression?
MAOA
Describe the role of MAOA
One gene which has been linked to aggression is the gene coding for the production of monoamine oxidise A (MAOA). MAOA regulates the metabolism of serotonin in the brain, and low levels of serotonin are associated with aggressive behaviour. Thus, low levels of MAOA are also associated with aggression. Studies of violent criminals have found that they often have a defect in the gene that produces MAOA.
Name a Study which supports the role of MAOA
Brunner et al.
Discuss Brunner et al.’s findings
Brunner studied a Dutch family in the 1980s, and found that most of its male members behaved in a particularly violent and aggressive manner. and a large proportion had been involved in serious crimes of violence, including rape and arson. These men were found to have abnormally low levels of MAOA, which shows evidence of a relation between genes and aggression.
What study backs up the difficulty of determining the role of genetic factors in aggression
Caspi et al.
Discuss Caspi et al.’s findings
Caspi studied 500 male children, who showed links between MAOA and Aggressive Behaviour. The research discovered a variant of the gene associated with high levels of MAOA and a variant associated with low levels. Children with low levels of MAOA were significantly more likely to grow up to exhibit antisocial behaviour but only if they had been maltreated as children. Children with high levels of MAOA who were maltreated and those with low levels who were not maltreated, did not display antisocial behaviour. This shows that it is the interaction between genes and environment, that determines behaviours such as aggression.
Name another study which supports the link between MAOA and increased aggression
MAOA is thought to increase aggressive behaviour by affecting levels of neurotransmitters. Research support for this comes from Cases et al., who disabled the MAOA gene in mice. They found that in these mice, levels of serotonin and dopamine (both of which are associated with higher levels of aggression) increased and aggression increased. This suggests that MAOA reduces aggression by regulating levels of these neurotransmitters.
AID: Animal Research
Studies such this one on non-human animals have an important role in helping us understand aggression in humans, as genes can be manipulated and the effects of these manipulations can be observed. This allows us to precisely identify the role of specific genes. However, commonly-used animals such as mice have a different genome and physiology to humans, so the effects of genes may be different. The use of animals in such studies can also be considered unethical.
AID: Real World Application
This research has an important real-world application. There have been suggestions that if people’s genes predispose them towards aggressive behaviour, genetic engineering should be used to change their genes and reduce this risk. Some have even suggested more extreme measures to prevent the heritability of such genes, for example by chemical castration. However the labelling of an individual as dangerous based on their genetic inheritance poses serious ethical questions.
