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Contemporary Study: Brendgen et al (2005) Examining Genetic and…
Contemporary Study: Brendgen et al (2005)
Examining Genetic and Environmental affects on aggression
Aim
Whether there's a difference between physcial and social aggression in children and whether the link is down to genetics or social situations by comparing MZ/DZ twins.
To what extent physical aggression is overtaken by social aggression during early childhood,
Sample
234 pairs of twins from the Quebec Newborn Study
Used for when the children were 6 years old
44 sets of identical male twins
50 sets of identical female twins
41 sets of non-identical males
32 sets of non-identical females
67 sets of mixed gender
IV
Looks for correlation between:
Aggression scores for identical twins
Aggression scores for non-identical twins
Teacher ratings on children's aggression
Peer ratings on children's aggression
DV
Teachers rating on social and physical aggression
Peers rating on twins who fit the various descriptions given
Method
Natural Experiment
Results
There was
positive correlation
between physical and social aggression.
There was a
higher correlation
between the ratings of MZ twins on physical aggression than DZ.
There was a
equal correlation
on the rating of social aggression between MZ and DZ.
PA
63% genetic
SA
20% genetic
Conclusions
Environmental conditions interact with genetic factors in terms of aggression.
Physical aggression (60%) is mostly nature while social aggression (20%) is mostly nurture.
Genetics might give children a general disposition towards aggression - SA comes if they're in an environment which encourages it.
Evaluation
Strengths
Brendgen used an established questionnaire with fixed questions = easily be replicated and makes the study reliable.
If social aggression is linked to environment, we can reduce the effects of verbal bullying, gossiping etc by using early intervention and workshops to help them be less aggressive.
The study avoids taking a reductionist view of human behaviour as it looks at both genetics and environment - links with findings of Bandura and Raine et al.
Weaknesses
The allocation of MZ and DZ was based largely on appearance = not 100% reliable as DZ twins could've been in the MZ condition.
If social aggression is linked to environment, it might also make parents sensitive in knowing they have a role in their child's aggression, making it socially sensitive research.
One twin might get stereotyped based on the other twin's behaviour so teacher and peer ratings might have been influenced by stereotypes with both children being given the same rating regardless of behaviour = reduces validity
Procedure
The teachers were given questionnaires to rate each child on a 3-point scale (0 = never, 1 = sometimes, 2 = often) on 6 statements:
says bad things or spreads nasty rumours
gets into fights
The peers were given photos of the children and were asked to circle photos of 3 children which best fit the descriptions:
hit, bites or kicks others
gets into fights
Social Aggression
tries to make others dislike the child
spreads nasty rumours or says bad things about another child
makes friends with other children for revenge
Physical Aggression
gets into fights
physically attacks others
hits, bites or kicks others