3.3 brendgen Flashcards
what are the aims of brendgen’s study?
contemporary study
to discover
- the extent to which social and physical aggression are explained by genetic and environmental influences
- whether the overlap between social and physical aggression is explained by the direct effect of one type of aggression on the other
describe the sample used in brendgen’s study
234 pairs of twins the longitudinal quebec newborn twin study (QNTS) at 72 months (6 years)
describe the procedure used in brendgen’s study
- researchers used twin study design to calculate correlations between mz and dz twins rated for socailly and physically aggressive behaviour
- teacher ratings - 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 ‘says bad things or spreads nasty rumours about others’ (social) and ‘hits, bites or kicks others’ (physical)
- peer ratings - levels of twins’ social and physical aggression were also rated by their classmates. first, a research assistant checked that each child could recognise everyone in their class. each classmate was given a booklet of photographs of all the children in their class and asked to nominate the three children on each page who best matched a description of behaviour. there were two descriptions for social agg (‘tells others not to play with a child’ and ‘tells mean secrets about another child’) and two for physical aggression (‘gets into fights’ and ‘hits, bites or kicks others’
what were the two descriptions for social and physical aggression in peer ratings?
There were two descriptions for social aggression
- ‘tells others not to play with a child’
- ‘tells mean secrets about another child’
There were two descriptions for physical aggression
- ‘gets into fights’
- ‘hits, bites or kicks others’.
what were the descriptions for social and physical aggression in teacher ratings?
Social
- ‘says bad things or spreads nasty rumours about others’
Physical
- ‘hits, bites or kicks others’
describe the results of brendgen’s study
a) Teacher ratings;
* Physical aggression was 63% genetic and 37% non-shared environment (friends/ school)
* Social aggression was 20% genetic, 20% shared environment (home) and 60% non-shared environment (friends/ school)
Peer ratings were very similar.
* b) Teacher questionnaires revealed that overall boys were rated more physically aggressive and girls more socially aggressive but this not seen in children’s ratings.
c) There was a moderate correlation between peer ratings and teacher ratings; children seen as physically aggressive were also described as socially aggressive.
describe the conclusions of brendgen’s study
- Physical aggression is caused by 50-60% genetic factors (but influenced by a child’s environment), whereas social aggression seems to be caused more by environmental factors (80%), only 20% genetic.
- Children may be genetically predisposed by their genes to behave aggressively but the environment they grow up in may lead to more social aggression.
brendgen - generalisability
P - high generalisability
E - used a large sample size of 234 twin pairs from quebec
T - this sample is large enough to account for ppt variables in the target population of twins
P - low generalisability
E - The sample consisted of 234 twins from the longitudinal Quebec Newborn Twin Study (QNTS) and only goes up to 6 years
T - This will not represent other ages (such as adults) or other cultures and their differing environment
brendgen - reliability
high
P - High reliability as standardised scales were used to measure aggression.
E - For example, teachers ranked statements on a 3 point scale (0- never 1- sometimes 2- often) to statements such as ‘two what extent does this child get into fights’.
T - This offers a consistent measure of aggression and can be replicated to test for consistent results
brendgen - reliability
low
P - Low
E - The allocation of whether twins were MZ or DZ was based purely on observation of appearance
E - This would mean there may be inconsistencies with who were correctly and incorrectly identified as MZ or DZ
brendgen - application
P - The study could lead to effective interventions that reduce aggression
E - Conclusions suggest that interventions should focus on preventing or reducing physical aggression in early years. Interventions based on this research could disrupt the transformation of physical aggression into social aggression, ultimately reducing both types
T - Useful to society, can decrease aggression
brendgen - validity
P - Potentially invalid assumptions as it is based on the equal environments assumption
E - This states that MZ and DZ twins experience similar treatment to the same extent, however, this may well be wrong. E.g it’s likely that many parents of DZ twins behave more aggresively towards one child than the other because the twins are dissimilar but this is much less true for MZ twins who are similar.
T - There are many ways in which this assumption may be violated, seriously underminind the validity of the twin study method
brendgen - ethics
P - Low
E - The study gets children to look at pictures of their classmates and judge them. This might have a bad impact on friendships, especially if the children told each other afterwards who they had selected as the “hitter and biter” or the “tale-bearer”. This could lead to hurt feelings or revenge
T - This goes against the social responsibility of ethical research and might create risk for the children who participated.
