contemporary study: brendgen

Question 1

what is the aim?

Answer 1

investigated the aggression in MZ and DZ twins to discover:
- the extent to which social and physical aggression is explained by genetic and environmental factors
- whether the overlap between social and physical aggresssion is explained by the effect of the other type of aggression

Question 2

what was the procedure used?

Answer 2

the researchers used a twin study design
- 234 pairs of twins from the longitudinal quebed newborn twin study which collected data from twins regularly
44 male MZ twins and 50 female MZ twins
41 male DZ twins and 32 female DZ twins

Question 3

what did the teacher ratings do?

Answer 3

kindergarten teachers rated the social and physical aggression of each child on a three-point scale NEVER SOMETIMES OFTEN in response to items such as saying bad things (social) or hitting (physical)

Question 4

what did the peer ratings do?

Answer 4

a research assistant checked that each child could recognise everyone in their class and had them nominate children who best matched a description of behaviour e.g. tells others not to play with a child (social) and gets into fights (physical)

Question 5

what were the findings?

Answer 5

• 20 - 23% of social aggression was explained by genetic factors
• physical aggression was mostly explained by genetic factors and partly by non-shared environmental factors and social aggression mostly by non-shared environmental factors
• moderate correlation between social and physical aggression (mostly genetic)
• high physical aggression = high social aggression but not the other way around

Question 5

what is a weakness?

Answer 5

based on equal environmental assumptions
- MZ and DZ may not experience similar treatment to the same extent
MZ twins are more likely to be treated similar due to their similar appearance

Question 5

what is a strength?

Answer 5

the researchers used ratings of aggression from two sources
- both teachers and students
- provides reassurance that they are valid and reliable

Question 6

how can it be applied?

Answer 6

could lead to effective interventions to reduce aggression?
- interventions should focus on preventing or reducing physical aggression in the early years
- brendgen et al suggest that future studies could identify the factors that block the path from physical to social aggression

Question 6

what is the competing argument?

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Answer 6

many of the ways MZ similarity occurs is irrelevent to the behaviour being investigated. DERKS et al. conducted a study of aggression in adolescent twins and used statistical methods to show that the assumption is not valid