Brendgen Flashcards
What is the aim of Brendgen?
To what extent is the variance of social aggression explained by genetic, shared environmental, or non-shared environmental factors?
Is there a relationship between physical and social aggression?
What is the sample of Brendgen?
322 twin pairs from Quebec but 234 completed the full study
Physical resemblance was used to identify them as MZ or DZ at 18m of age
123 twin pairs obtained DNA and showed a 94% agreement with their assignment
Followed from birth until the age of 6 (5, 18, 30, 48 and 60 months and 6 years)
What is the procedure of Brendgen?
Questions were given in either English or French (across 409 classrooms)
Teachers rated the children’s level of social aggression and physical aggression ‘‘tries
to make others dislike a child’’
With regard to physical aggression, the teachers indicated to what extent the child ‘‘gets into fights’’
Responses were given on a 3-point scale
(never, sometimes, often) from Preschool Social Behaviour Scale (PSBS-T)
Children asked to circle the photos of three children who best fit a behavioural descriptor
Social aggression: ‘‘tells others not to play with a child’’
Physical aggression: ‘‘gets into fights’’
What are the results of Brendgen?
Boys more physically aggressive than girls (teachers)
Higher correlation from MZ to DZ twins on Physical aggression
62% of the genetic factors affecting social aggression also effect physical aggression
The correlation seen between Physical and Social aggression (0.79) in twins was mainly due to genetics rather than shared environment
What did Brendgen conclude?
Children seem to move from physical to
social aggression as they age (possibly to avoid punishment, possibly because of developing skills)
About 50-60% of the difference in physical aggression was due to
genes and the rest non-shared environment
What is a strength of Brendgen regarding the sample?
Large sample for twin studies (234 twin pairs) so results about physical and social aggression are more generalisable to a wider population
What is a weakness of Brendgen regarding the sample?
Did not include enough of each type of twin of each gender to effectively study gender
differences as initially planned
Why is it good that Brendgen used measures by both the teachers and children?
Allows them to check the scores against each other getting inter-rater reliability so we can check the reliability of the results comparing the teacher and child scores
Why might it not be good to use a 3 point scale?
Sometimes, often and never is subjective judgement which might lower the validity as different teachers may interpret these words differently
Why is it good that children were told not to share answers?
Reduces demand characteristics so the results about the concordance of aggression between the twins is more valid
Why might using 3 point scale and circling photos be a weakness of Brendgen’s study?
Quantitative data doesn’t provide lots of depth (e.g. reasons for aggression in different situations) so we don’t get a lot of understanding on how/why the children demonstrated their
aggression
