Discuss the Role of Genetic Factors in Aggression

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Outline and evaluate genetic factors in aggression (8 + 16) It has often been suggested that genes have an influence on human aggression. Most people have 46 chromosomes, but in 1961, Sandberg identified the 47 XYY karyotype, and found that it is possible for a male to have an extra Y sex chromosome, making them XYY. The research of Court-Brown suggested that those with the XYY makeup should be hospitalised due to the increased likelihood of aggressive behaviour. This however was an early assumption that Court-Brown made prior to the examination of patients and although the statement was later retracted, the view that XYY males were more aggressive had already been incorporated into the thinking of many scientists. In later research Theilgaard aimed to investigate the link between the XYY chromosome and aggression by examining the personality traits of a sample of XYY men, comparing them to XY men. The research focused on levels of aggression in the two groups, but found that the only characteristic that was shared by all XYY men was their above-average height. Levels of aggression fluctuated, so no definitive conclusions could be drawn. Overall, research in this area lacks reliability and has shown no consistent link between genotype and aggressive behaviour. Also much of the research used samples of prison inmates so could be criticised as lacking population validity. Therefore any link, however weak, between XYY and aggression would lack generalisability. The fact that prison populations also include XY males suggests that genetics alone are not responsible for any aggressive behaviour that may have led to them being imprisoned and not all inmates are imprisoned because of aggressive, violent crimes. Theilgaard argued that although XYY males gave more aggressive interpretations in thematic apperception tests and therefore seemed more aggressive it didn’t
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