Brengden Et Al (2005) Twin/ Contemporary Study

Question 1

Aim

Answer 1

Difference betweeen physical/ social aggression in 6 year old children and if it is correlational to genetics between MZ and DZ twins

Question 2

Procedure (2)

Answer 2

Teachers- rate twin on three point scale on physical and social aggression = two overall scores
Peer ratings- shown photos of classmates and asked to circle 3 who best fit description

Question 3

Sample (6)

Answer 3

Originally, 322 pairs but by age 6, 88 pairs dropped out leaving 234 pairs of twins:
- 44 MZ males
- 50 MZ females
- 41 DZ males
- 32 DZ females
- 67 mixed DZ twins

Question 4

Results (3)

Answer 4

Teachers said boys + physically aggressive and girls + socially aggressive
Peer said boys + physically and socially aggressive

MZ corr. for physical was x2 as high as same sex DZ corr.
DZ twins more influenced by environment

SA less linked to aggression as both types of twins seemed to be equally affected by surroundings unlike w. PA

Question 5

Conclusion (2)

Answer 5

Genes
- 50-60% of PA
- 20% of SA

‘Non-Shared Environement’
- 40% PA
- 60% SA (20% attributed to shared environment e.g. parenting strategies)

Question 6

Generalisability (5)

Answer 6

Population validity
Culture bias
Ethnocentrism
Sample attrition
Representative

Question 7

Reliability (6)

Answer 7

Established questionnaires
Replicable
Inter-rather reliability
Strong correlation
Language differences
Subjectivity

Question 8

Application (3)

Answer 8

Early intervention
Workshops
Educating parents

Question 9

Validity (5)

Answer 9

Assumptions
Ecological validity
Population validity
Natural experiment
Reductionist

Question 10

Ethics (4)

Answer 10

Presumptive consent
Impact friendships
Social responsibility
Psychological trauma