Discuss the Role of Genetic Factors in Aggressive Behaviour

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everything you need to know for an essay on the role of genetic factors in aggressive behaviour
chloe.brandon
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chloe.brandon
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What does this biological approach of aggression encompass? the idea that aggressive behaviour is due to an individuals biological makeup as opposed to a product of environmental factors
What kind of question does this bring about? whether aggression is nature or nurture
What is one way to see whether aggression runs is a genetic trait? twin studies
What is the difference between monozygotic and dizygotic twins? monozygotic twins are identical and share all of their genes whereas dizygotic twins are non-identical and share 50% of their genes
What do researchers do in twin studies? compare the degree of similarity for a particular trait (aggression) between sets of MZ twins to the similarity between sets of DZ twins
What does it mean if MZ twins are more alike in terms of their aggressive behaviour? this should be due to genes rather than the environment
What have most twin studies focused on? criminal behaviour
What did one of the few studies like one by Coccaro et al (1997) study? specifically aggressive behaviour using adult twin pairs
What did they find? 50% of the variance in direct aggressive behaviour could be attributed to genetic factors
How can adoption studies help us to see whether aggression is genetic? they help to untangle the relative contributions of environment and heritage
What happens if a positive correlation is found between aggressive behaviour in adopted children and aggressive behaviour in their biological parents? you can assume the aggression is due to genetics
What happens if a positive correlation is found between aggressive behaviour in the adoptee and the aggressive behaviour in the rearing family? you can assume that the aggression is due to environmental factors as the adoptee doesn't share any genes with the adoptive family
What did Hutchings and Mednick (1975) do? conducted a study on over 14,000 adoptions in Denmark
What did they find? a significant number of adopted boys with criminal convictions had biological parents (particularly fathers) with criminal convictions
What does this provide evidence for? a genetic effect
Is there a gene for aggression? not specifically an individual gene
What is there? a gene responsible for producing a protein called monoamine oxidase A (MAOA) has been associated with aggressive behaviour
What does MAOA do? regulates metabolism of serotonin in the brain and low levels of serotonin are associated with impulsive and aggressive behaviour
In the 1980's what did a study of a Dutch family find? many of its male members behaved in a particularly violent and aggressive manner, and a large proportion had been involved in serious crimes of violence including rape and arson
What was it discovered that these men had? abnormally low levels of MAOA in their bodies and a defect in this gene was later identified
Who provided this study and its findings as a means of demonstrating the role of genetic factors in aggressive behaviour? Brunner et al (1993)
What did Caspi et al (2002) do? conducted a study demonstrating an interaction between genes and the environment
What did they link? MAOA to aggressive behaviour
What did their study involve? 500 male children
What did the researchers discover? a variant of the gene associated with high levels of MAOA and a variant associated with low levels
What were those with low levels of MAOA more likely to exhibit? antisocial behaviour but only if they had been maltreated as children
Which children did not display antisocial behaviour? children with high levels of MAOA who were maltreated and those with low levels who had not been maltreated
What does this show? that there is an interaction between genes and the environment which determines behaviours such as aggression
Who provided research support for the genetic basis of aggression? Miles and Carey (1997)
What did they do? they carried out a meta-analysis of 24 twin and adoption studies
What had most studies relied on? parental or participants' self reports or aggressive tendencies, although some involved observation of aggressive behaviour
What did the results suggest? a strong genetic influence that could account for as much as 50% of the variance in aggression
What was notably important? age differences, with both genes and family environment being influential in determining aggression in youth, but at later ages the influence of rearing environment decreased and the influence of genes increased
Who conducted a later meta-analysis? Rhee and Waldman (2002)
What did they do? they combined the results of 51 twin and adoption studies
What did they also conclude? aggressive antisocial behaviour was largely a product of genetic contributions
What did both meta-analyses have in common? several variables, including the age of participant and assessment method for aggression moderated the genetic influence on aggression
What does this suggest? although genetic factors play a significant part in the development of aggressive behaviours, the influence of other factors affects their expression
What have many of the studies in this area focused on? individuals convicted of violent crime
What is the first problem that arises when trying to draw meaningful conclusions from these studies? the participants themselves, convictions for violent crimes are relatively few compared to the vast number of violent attacks that never result in a conviction
What does this mean? they therefore represent just a small minority of those regularly involved in aggressive behaviour
What is the second problem? offenders designated as 'violent' on the basis of a court conviction are not necessarily the most persistent offenders, for example, a convicted murderer would be designated as violent for one offence, despite possibly having a lifetime free of crime
What might this explain? why so many studies have found little or no evidence of heritability for violence
What is another limitation? It is difficult to determine the role of genetic factors
Why is this difficult? 1. more than one gene usually contributes to given behaviour 2. there are many non-genetic influences as well as genetic which influence the manifestation of aggressive behavior 3. these influences interact with each other, genetic factors may affect which environmental factors have an influence and vice versa
What is a problem with assessing aggression? many studies have relied on either parental or self-reports of aggressive behaviour, whilst others have made use of observational techniques
What did Miles and Careys' meta analysis that was described previously find? the mode of assessment was found to be a significant moderator of aggressive behaviour
What did they find about the studies that used parental or self-report techniques? genetic factors explained a large proportion of the variance in aggressive behaviour
What did observational studies show? less genetic contribution and a greater influence of environmental factors
Why is animal research valuable? rodents offer the advantage of experimental manipulation to test the effects of specific genes on aggressive behaviour
What may manipulations involve? selective breeding programmes and 'knockout' techniques (where a single gene is eliminated from a group of experimental animals in order to study its effect)
What is an example of a study that has potential for an understanding of human aggression? Young et al (2002)
What did the researchers claim? to have identified a genetic mutation that causes violent behaviour in mice
What effects did the mutation nicknamed 'fierce' have on mice? extremely violent behaviour towards other mice
How is this relevant to human aggression? a counterpart of this gene does exist in humans although its precise function is unknown
What is the real world application? if people are predisposed towards aggressive behaviour or violent crime, then questions about the treatment of such behaviours inevitably arise
What do some people suggest? genetic engineering
What do other people suggest? the problem should be dealt with more directly whilst violence remains at the forefront of public concern, for example through chemical castration
What is characteristic of the conclusions made through research in this field? they are of an extremely tentative nature and have far-reaching ethical consequences of labelling an individual as a threat to society on the basis of their genetic inheritance
What is important? an awareness of the limitations of these studies
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