genetic Explanations Flashcards
What are the two types of MAOA gene and how do they differ?
1) low activity form (MAOA-L). People with this produce less of the MAO enzyme hence they do not remove as much dopamine and serotonin.
2) high activity form (MAOA-H) produce more of enzyme hence remove more dopamine and serotonin.
People with low form are thought to have more aggressive tendencies.
What did Cases et al find supporting MAOA gene theory?
Studied mice genetically engineered to lack MAOA gene. Found that the mice had dramatically altered levels of serotonin and showed enhanced aggression when adult males.
What did Mattson find similar to Cases?
Found that MAOA deficient male mice attacked new mice introduced to their cage. Female mice with the defective gene behaved normally suggesting the effect may only be inherited in males.
What did Brunner find supporting MAOA GENE?
Discovered a defective MAOA gene in a Dutch history with a previous history of male violence. Suggests that defective MAOA gene also plays a role in human aggression.
What did Moffit find criticising this?
Found that aggressive behaviour was 9x more likely in participants with MAOA-L gene if they had suffered abuse as children. participants who suffered abuse with MAOA-H were no more likely to behave aggressively than a control group suffering no abuse.
Outline the MAOA gene and its link to aggression:
MAOA (monoamine oxidase A) regulates the enzyme MOA (monoamine oxidase A) this enzyme breaks down neurotransmitters like serotonin and dopamine which are associated with mood. A build up of these neurotransmitters can cause a person to respond aggressively to situations. MAOA gene regulates the enzyme which removes excess amounts of these neurotransmitters.
Outline the link between PET-1 gene and aggression:
It is thought that people who are over aggressive/anxious may be missing the PET-1 gene. The gene was removed from specifically bred mice and they found the mice had heightened levels of both anxiety and aggression. When the mice were given territory, the response time to attack an intruder was significantly lower than a natural mice.
What did Deneris et al suggest regarding the PET-1 gene and human behaviour ?
Believes that the behaviour of the genetically engineered mice is strikingly reminiscent of some human psychiatric disorders characterised by aggression/ anxiety. The gene appears to be important in the development of serotonin neurotransmitters in the foetus.
What did McGue et al find in his twin study experiment regarding PET-1 gene?
Found a (+0.43) correlation for MZ twins and (+0.30) for DZ twins on aggression scales. Suggests genes do play a part in aggressive tendencies as the nurture factor has been accounted for, being both MZ and DZ twins are generally raised in a similar environment.
What did Plomin et al find regarding twin studies and PET-1 gene ?
Replicated Bobo doll study using sets of twins, found no difference between levels of aggression in MZ and DZ twins.
What is an IDA point for the genetic explanation of aggression ?
Focusing on the role of genetic factors ignores the idea that aggression can be learnt. Fails to account for environmental factors which have been shown to influence behaviour (e.g. Milgram and Bandura)
