bregdan 2005 twin study Flashcards
when was the study?
2005
what awas the aim of the study?
compared to physical aggression to what extent social aggression was down to genetics, shared or non ahred environment
what type of design was the study?
a ongoing longitudinal study
where were the participnats from?
montreal cnanda
what years did the participants have to be born between?
1995-1998
how old were the participnats?
6 years old
what wa sthe attrition rate per year?
2%
how many twins were there in total?
234
how many female mz twins was there?
50
how many male mz twins were there?
44 94 mz
how many female dz twins were there
32
how many male dz twins were there?
41 73 dz
how many mixed dz twins were there?
67
when was the sample assessed?
5, 18, 30, 48 and 60 months
final data taken at 6 years
how was written consent gained?
written from parents
how many children were in the same class?
who rated the students and on what?
who rated the students and on what?
teachers on social and physical aggression
what did the teachers use to rate the students?
the preschool behaviour scale and direct and in direct aggression scale
how else did they rate the students?
using a three point scale
0=never
how was peer ratings conducted?
children were given a booklet of every classmates face they had to circle 3 students that best fit for descriptors
2 physical 2 social
nominators added up and turned into aggression scores
who was found to be more physically aggressive?
boys
what was found about physical aggression?
that mz scores were twice as high as dz for both teacher and peer ratings
for social aggression what was found?
that mz and dz scores were similar showing that shared environment may explain S aggression
what was the overall conclusion?
that 50-60% of physical aggression was due to heritable factors
environmental factors influence SA
high level of physical aggression lead to high S but not other way round
what wa the overall correlation?
it was modest correlation (not strong)
what does a modest correlation show?
that behaviour is not purely linked to genetics
non shared environment must play a part
what percent of social aggression cam be explained by genes?
20%
what percent of physical aggression can be explained by genes?
50-60%
