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Brendgen Et Al 2005 - Coggle Diagram
Brendgen Et Al 2005
Procedure
- Twins assigned MZ or DZ based on physical appearence
- Teacher rates were based on agreement with a series of statements
- Peer ratings based on asking each child to circle pictures they thought matched different descriptions
Evaluation
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Validity
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Study avoids taking a reductionist view of human behaviour, looks at genetics but takes environmental factors into account
Reliability
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inter-rater reliability: two researchers per classroom, strong correlation between findings
language differences may have made findings unreliable, as original ones in French so English translations may be unreliable
Allocation of zygosity based largely on appearance, not DNA
Ethics
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Judging peers based on booklets has the possibility to damage friendships, leading to hurt feelings or revenge
However, research for 'common good' and research may maximise benefit for all school children
Generalisablitily
- Large sample which causes anomolies to be averaged out which makes it generalisable
- Twins are a unique population which may cause it to be less generalisable
- Sample consisted of only six year olds meaning its only representitive for that age group
- 88 pairs of twins dopped out causing sample attricion and making it less generalisable
Aim
- To investigate is physical aggression is caused by genes or the environment
- To see if social aggresion shares the same heritability as physical aggresion and if one type of aggresion leads to the other type
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Sample
- Population sample of 234 twin pairs from Quebec
- 94 six year old MZ twins
- 140 six year old DZ twins
- All born between November 1995 and July 1998
Results
- Scores for social and physical aggression were added, producing 2 overall scores
- A Chi squared tests compared ratings and found no significant differences
- Genetic heritability counted for 54% of physical aggression
-teachers rated boys as more physically aggressive and the girls as more socially aggressive; peer ratings from classmates showed the boys to be both more physically and more socially aggressive.
- The MZ twins' correlations for social aggression were similar to the DZ twins' correlations which shows social aggression is less linked to genetics, because both types of twins seemed to be equally affected by their surroundings, unlike with physical aggression
Conclusion
- Physical Aggression is mostly genetic
- Social aggresion is mostly environmental
- Physical aggression becomes social aggresion if an enviroment encourages it