Genetic factors in aggression Flashcards
Twin studies
If MZ twins are alike than DZ twins, it suggests a strong genetic influence. Studies of adult twins suggest that at least 50% of the variants in aggression can be explained in terms of genetic factors.
Adoption studies
Adopted boys with criminal convictions had biological parents with criminal convictions too, providing evidence for a strong genetic link.
What is the research support for a strong genetic influence between genes and aggression?
A meta-analysis found that younger people are more influenced by both genetics and the environment where as in older people genetic influences are more important in determining aggressive behaviour.
However, what are the problems with miles and carey’s meta-analysis?
The method used to assess aggression was self-report which reduces the reliability of the study. Those who self-report reported higher levels and hence shows a stronger genetic link
The age of the participant also had an effect on the aggression displayed, meaning that the study suggest genetics play a part in the development of aggressive behaviours but the expression is influenced by other factors.
Is there a gene for aggression?
MAOA has been associated with aggressive behaviour. MAOA regulates the metabolism of serotonin and low levels of serotonin are associated with aggressive behaviour. A study of a violent Dutch family found that the men had low levels of MAOA, indicating a link.
Could aggression be an interaction between genes and the environment?
A study concluded that boys with low levels of the MAOA were significantly more likely to display aggressive behaviour but only if they were maltreated as children. Suggesting an interaction between the genes and the environment that determines aggression.
What are the problems of sampling in genetic studies?
Many ‘violent’ people are never convicted and so those studies represent a small minority of those regularly involved in aggressive behaviour.
People labelled as ‘violent’ may not be the most serious of offenders e.g someone committing a murder may have a life time of no crime whatsoever, again, only showing the minority. A reason why many studies have found little evidence of heritability for violence.
Reduces validity
What are the difficulties of determining the role of genetic factors?
More than one gene contributes to any given behaviour.
There are other non-genetic factors that can influence on the manifestation of aggressive behaviour. And these factors can interact with each other.
How has animal research helped us in this area?
Researchers can eliminate a single gene from an experimental group to see its effects. Meaning researchers can identify genetic mutations that cause aggressive behaviour in mice. Comparing that to humans, we can see whether it’s the same, exact function is unknown yet.
Genetics have found a link for violent crime or not?
Research suggests that inherited temperament of personality characteristics make some people more likely to commit violent crimes. Adoption studies have found that shown that the highest rates of criminal violence occur when both biological and adopted parents have a history of violent crime.- showing an interaction between genes and the environment.
Studies have shown genetic influences were significant in cases of property crime but not violent crime.
Real world application of determining whether someone will be aggressive or not
People have suggested genetic engineering or even chemical castration to treat potential violent offenders.
Labelling is also an issue here with people taking part in self-fulfilling prophecy because of it. This raises ethical issues as people are labelled as something they are not, even when the evidence is not 100% conclusive.
What are the 4 evaluation points of this?
problems of sampling
real word application-labelling
value of animal research
difficulties in determining the role of genetic factors
