Aggression L3 Genetic Factors Flashcards
What is the link between genes and aggression?
- Evidence to suggest that there is a link between genes and aggression
- This is shown through twin and adoption studies, along with specific genes which are related to aggression
What did early psychologists believe was the genetic cause of aggression was?
- Main difference between men and women lies in their genotype, with 23 pairs of chromosomes, where XY determines us as male, and XX determines us as female
- They believed the genetic cause of aggression was in the Y chromosome and examined individuals with a genotype of XYY
What were individuals with two Y chromosomes called?
Super Males, Court-Brown discovered 314 patients had the XYY chromosome presentation and he put forward the view that these patients should remain in hospital due to their increased likelihood of aggressive behaviour
Twin Studies in Aggression?
- Studied pairs of male adult twin who were either MZ or DZ and compared the concordance rates for aggression
- Found for physical assault MZ twins had a concordance rate was 50% and for DZ twins it was 19%
- For verbal aggression it was 28% for MZ twins and 7% for DZ twins
- Both suggest a genetic component to aggression
Adoption Studies in Aggression?
- Carried out a meta-analysis of adoption studies of direct aggression and antisocial behaviour
- They found that genetic influences accounted for 41%, suggesting the role of genetics to be important in aggressive behaviour
What Candidate Genes are linked to Aggression?
- The MAOA gene, which is responsible for the protein monoamine oxidase
- This allows the metabolising of noradrenaline, serotonin and dopamine and dysfunction in this gene means the neurotransmitters are not broken down properly
What is the low activity version of the MAOA gene called?
- MAOA-L gene, means they are more likely to be aggressive
- It is also known as the ‘warrior gene’
Expand on dysfunction in the metabolising process?
- If noradrenaline is not metabolised properly we end up with too much adrenaline, causing hypersensitivity in the fight or flight response and individuals may overreact to stimulus, perceiving a threat where one does not exist
- Dopamine not being broken down properly leads to increased levels of aggressive behaviour
- Serotonin has a calming influence and low levels are linked to reduction of control over impulsive behaviour
Strengths of Genetic Factors in Aggression? (3)
- Aggressive Criminal Behaviour in MZ Twins
- MAOA gene in mice
- Dutch family
Aggressive Criminal Behaviour in MZ Twins (+)
Role of genes shown by a much higher concordance rate of physical aggression in criminal behaviour in MZ twins compared to DZ twins
MAOA gene in mice (+)
- Selective Breeding was done in mice, knocking out the MAOA gene
- The MAOA knockout mice showed increased aggression and lower levels of serotonin, showing relationship between genes and neurotransmitters
- Mice were given fluexotine to raise serotonin levels and their behaviour returned to normal
- Shows the role of the MAOA gene in aggression
Dutch family (+)
- Studied 28 men from a large Dutch family who were involved in impulsive violent criminal activity, e.g rape, attempted murder, and physical assault
- They all possessed the MAOA-L gene
Weaknesses of Genetic Factors in Aggression? (2)
- XYY Chromosomes
- Lack of validity in MZ twin studies
XYY Chromosomes (-)
- Undertook research into the men with XYY chromosomes
- Found that this was implicated in an increase in the height of individuals, not aggression
- There is no link between XYY Chromosomes and aggression
Lack of validity in MZ twin studies (-)
- MZ twins may share the same experience of parents and significant others as they are genetically the same
- DZ twins might not as they are not the same sex nor entirely genetically similar
- Therefore twin studies do not account for similar experiences and upbringing of MZ twins, does not emphasise the environmental similarities
