How do researchers study genetic Draw on your factors?research methods Twin Studies knowledge - Monozygotic twins share all of their genes where as dizygotic Adoption Studies twins share only about 50% - Researchers compare the degree of similarity for-Separate the effects of genes aggression to look for afrom that of the environment concordance rate.-If there’s a +ve correlation in - If the concordance rate isaggressive behaviour in higher in MZ twins it suggestsadopted children and their the behaviour has a geneticbiological parents it suggests componentthe behaviour has a geneticcomponent
Genetics and AggressionStudies often find that aggressive children have aggressive parentsMiles & Carey (1997)Carried out meta-analysis of 24 twin and adoption studiesResults suggested a strong genetic influence that could accountfor as much as 50% of the variance in aggression
Genetics and AggressionStudies often find that aggressive children have aggressive parents Other research focussed on the genes themselves and tried toidentify important characteristics of genes that might cause these aggressive tendencies – much of this research has focused on chromosomes Sandberg (1961) first identified the 47 XYY karotype. Whilst most normal individuals have 46 chromosomes (23 from each parent), it’s possible for a male to have an extra Y sex chromosome, making the XYY
Genetics and AggressionStudies often find that aggressive children have aggressive parents The research of Court-Brown (1965-1967) found that those with XYY would be ‘best hospitalised due to an increased likelihood of aggressive behaviour’ This was requested based upon common knowledge of traits associated with each of the sexes. Many textbooks and media depictions of the time adopted thisview contributing the widely held belief that XYY males are more aggressive
Genetic theory EvaluationAlternative ApproachFocussing so heavily on genetics ignores the behavioural approachFails to account for the role of the environmente.g. Bandura’s Bobo doll study demonstrated that children were more likely to exhibit aggressive behaviour when observed by a rewarded adult role modelThis suggests that environment and SLT may at least play a part in aggression.
Genetic theory Evaluation In addition to this: A replication of Bandura’s research using twins found no difference in correlations between MZ and DZ twins - Suggesting that aggression may be more a product of the environment
Genetic theory EvaluationAlternative ApproachNature Vs. NurtureAronson (1999) reported on non-violent theFocussing so heavily on genetics ignores behavioural approach societiesThis suggests thatfor the role of the environmentFails to account learning is more important thate.g. Bandura’s Bobo doll study demonstrated biology when explaining aggressionThis is critical as were if therelikelybiological that children even more are to exhibit influences Aronson’s researchobserved by a aggressive behaviour when shows that the environment can role model rewarded adult override themIf aggression is that environment and SLT may atThis suggests biological then it would not be least playspecific in implying aggression is learned culturally a part – aggression.
Genetic theory EvaluationNature Vs. NurtureMcGue et al (1992) correlation of MZ and DZ twins +0.43 for MZ, +0.30 for DZSuggesting that genes play some part in aggressive tendencies as MZ twins share more DNA than DZ twins – suggesting genes play a part
Genetic theory Evaluation A03 In addition to this: The reason MZ Bandura’s A replication of twins are more similar that DZfound research using twins might be due to environmental no difference in correlations factors – MZ twins are between MZ and DZ twins -more likely thatbe treated Suggesting to aggression may be more a product of the same the environment They share nature and nurture
Genetic theory Evaluation Theilgaard (1984) researched Lagerspetz (1979) bred 25the traits of XYY men compared generations of mice – in eachto XY men (including comparing generation the more aggressive aggression levels). mice were made to breed, It was found that no single similarly with the least aggressive characteristic (except height) was mice. associated with the XYY condition This resulted in 2 very different Suggests that the initial view strains of mice of XYY genotypes influencing aggression may have been One group were super-aggressive overemphasised and the other more docile