Genetic Factors in Aggression

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  • Created by: Emilyio
  • Created on: 17-04-16 19:16
(A01) Monozygotic (MZ)
Identical twins. They share 100% of their genes. They're formed from one fertilised eggs (or zygote)
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(A01) Dizygotic (DZ)
Non identical twins. Share 50% genes. Non-identical twins formed from 2 fertilised eggs (or zygotes)
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(A01) Is MZ twins are more likely are more alike in terms of aggression, what does this mean?
It means that it should be due to genes rather than environment.
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(A01) Coccaro et al 1997
Adult twin pairs found that nearly 50% of the variance in direct aggressive behaviour could be attributed to genetic factors
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(A01) If a +. correlation is found between the adoptees aggressive behaviour and the rearing family what effect is implied?
environmental
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(A01) Hutchings & Mednick 1975
Study of 14,000 adoptions in Denmark found a number of adopted boys with criminal records had biological parents(particularly fathers) with criminal convictions.
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(A01) What does MAOA stand for?
Monoamine Oxidase
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(A01) What does MAOA do?
Regulates the metabolism of serotonin in the brain, and low levels of serotonin are associated with impulsiveness.
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(A01) Dutch Family - Brunner et al 1993
1980's. Found that many of its male members were violent and aggressive manner, and a large proportion had been involved in serious crimes (**** & arson). They had low levvels of MAOA in their bodiesm and a defect in this gene was later identified.
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(A01) Gene-environment interaction - Caspi et al 2002
500 male children. Researchers found a gene associated with high levels of MAOA & a variant associated withlow levels. Low=antisocial only if maltreated. high=none. interaction between genes and environment creates aggression.
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(A01) What is the stress-diathesis model?
The claim that inherited temperamental or personality characteristics place some individuals more at risk of committing violent crime. A genetic predispotion of susceptibility.
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(A01) Adoption Studies - gene-environment interaction.
highest rates of criminal violence in adoption studies have shown that highest rates of criminal violence in adopted children ossur when both biological parents AND adoptive parents have violent crime history.
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(A01) Brennan & Mednick 1993
criminal history of an adoption male was comparedwith criminal history of both his biological and his adoptive fathers, found that genetic influences were significant in cases of property crime but not in cases of violent crime.
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(A02) 3 reasons whyit is difficult to establish genetic contributions :
1)more than one gene usually contributes to a given behaviour 2)there may be non-genetic influences 3)influences may interact, (gene-environment interactions) as shown by Caspi 2000
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(A02) issues with assesment - Self-reports or observation
Genetic factors explained a large proportion of aggression in studies that used parental, or self reports. However those who used observations showed significantly LESS genetic contribution and a greater influence of environment.
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(A02) Problems of assessment - Plomin et al 1981
Found no differences of in correlations between MZ & DZ twin pairs, suggesting that individual differences in aggression were more a product of environmental influences
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(A02) Methodological limitations -
Fail to distinguish between violent and non violent crime, making it more difficult to untangle the role of genetic factors in specifically Aggressive violence. AND fail to distinguish between criminals who are HABITUALLY violent and those who aren't
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(A02) Walters 1992
Meta-analysis found only a low - moderate correlation between heredity + crime with better designed & more recent studies finding less support.
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(A02) probling of sampling
Most studies are on violent crime. 2 difficulties: 1)violent crimes are relatively few and so represent just a minority. 2)violent criminals are not most serious, persistent offenders. (a murderer would be violent yet may have had a crime-free life)
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(A02) aggression in the public eye - real application
Findings in this area are too uncertain to state causal factors. People are concerned on treatment, some advocating genetic engineering. Awareness of limitations are important - unethical results of labelling a person a threat to society due to genes
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(A02) non human animals - Young et al 2000
Claimed to identify a genetic mutation that causes violent mice. Mutation nicknamed 'fierce' causes violent behaviour towards other mice. a counterpart of this is found in humans, though its function is unknown
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Card 2

Front

(A01) Dizygotic (DZ)

Back

Non identical twins. Share 50% genes. Non-identical twins formed from 2 fertilised eggs (or zygotes)

Card 3

Front

(A01) Is MZ twins are more likely are more alike in terms of aggression, what does this mean?

Back

Preview of the front of card 3

Card 4

Front

(A01) Coccaro et al 1997

Back

Preview of the front of card 4

Card 5

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(A01) If a +. correlation is found between the adoptees aggressive behaviour and the rearing family what effect is implied?

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Preview of the front of card 5
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