Genetic factors in aggression Flashcards
What have twin studies demonstrated?
That heritability (i.e genetic factors) accounts for about 50% of the variance in aggressive behaviour.
What did Emil Coccoro et al. (1997)?
Studied adult male monozygotic (MZ) and dizygotic (DZ) twins.
What was Coccoro’s hypothesis?
He expected to find greater similarities in aggression between MZ twins if aggression is mostly influenced by genetic factors because they have a greater degree of genetic similarity.
What were Coccoro’s findings?
For aggressive behaviour defined as direct physical assault, the researchers found a concordance rate of 50% for MZ twins and 19% for DZs. The corresponding figures for verbal aggression were 28% (MZs) and 7% (DZs).
State adoption studies findings.
Soo Rheen and Irwin Waldmin (2002) carried out a meta-analysis of adoption studies of direct aggression and antisocial behaviour. They found that genetic influences accounted for 41% of the variance in aggressive.
Define the term MAOA?
Monoamine oxidase a is an enzyme responsible for ‘mopping up’ neurotransmitters after they have been transmitted across a synapse. MAOA works on serotonin to break it down once it is transmitted. MAOA production is controlled by a particular gene, one variant of which has been nicknamed the ‘warrior gene’.
What can a dysfunction in the MAOA gene cause?
The low activity-variant of the gene means that it doesn’t break down serotine therefore there won’t be much to bounce therefore this affects the levels of serotonin in the brain, which increases the likelihood of aggressive behaviour.
Give evidence supporting MAOA theory.
Han Brunner et al. (1993) studied 28 male members of a large Dutch family who were repeatedly involved in impulsive violent criminal behaviours. The researchers found that these men had abnormally low levels of MAOA in their brains.
Gregory Stuart et al. (2014) studied 97 men involved in inflicting intimate partner violence (IPV), were part of a treatment programme. Men with the low-activity MAOA gene were found to be the most violent perpetrators of IPV.
Explain gene-environment (GxE) interactions.
The explanation that low MAOA activity is linked with aggression only in combination with an environmental influence, for example, a traumatic life event.
Give evidence supporting gene-environment (GxE) interactions theory.
Frazzetto et al (2007) found a link between the low-activity MAOA gene variant and aggression, but only in those who experienced childhood abuse. Those who had not been abused did not show high levels of aggression, even with the low-activity MAOA gene. This suggests an interaction between genes and the environment, supporting a diathesis-stress explanation.
What are the limitations of genetic factors in aggression explanations?
It is hard to isolate the role of genes from environmental influences.
There are likely to be multiple genetic influences on aggression.
Methods of measuring aggression differ significantly between studies and include, self-reports, parent and teacher reports and direct observation.
Give evidence for the difficulty in separating genetic and environmental factors.
Rose McDermott et al. (2009) showed that participants with the low-activity MAOA gene behaved aggressively in a laboratory-based money-allocation game, but only when they were provoked. Otherwise, they were no more or less aggressive than other participants.
Give evidence on there being multiple genetic influences on aggression.
Evangelos Vassos et al. (2014) in a meta-analysis couldn’t find any evidence of an association between any single gene and aggression. It was calculated that multiple genes interact to determine aggressive behaviour; casting doubt on it being a single candidate gene.
Why is the variety of methods to measure aggression a weakness?
This creates questions over the validity of the research findings as they vary making it difficult to draw valid conclusions about the role of genetic factors so reducing the support for genetic factors in aggression.
