brendegen (contemporary)

Question 1

brendegen’s aim?

Answer 1

• investigate relationship between social and physical aggression
• to what extent is the variance of social aggression explained by genetics / shared environment / non-shared environmental factors

Question 2

brendegen’s sample?

Answer 2

• originally 322 twins from Quebec
• 234 twins completed study due to attrition
• at 18 months physical resemblance was used to establish MZ or DZ
• for 123 twins DNA obtained and 94% were in agreement with assignment

Question 3

brendegen’s procedure?

Answer 3

1) longitudinal study (5/18/30/48/60 months/6 years)
2)focused on child and family relations
3) at 6 years : assessed children’s social adaption in kindergarten
4) questions given to teachers across 409 classrooms in both French and English depending on their native language (translations checked to maintain meaning)
5) teachers rated the children’s level of social and psychical aggression
- social : “spreads nasty rumours”
- physical : “gets into fights”
responses rated in the pre-school behaviour 3 point scale
6) children asked to circle photos of 3 children on who best fit behavioural descriptors or social / physical aggression

Question 4

brendegen’s results?

Answer 4

• higher correlation from MZ to DZ on physical aggression (genetics)
• similar ratings of social aggression from MZ to DZ (environment)
  -correlation between physical & social aggression (0.79) due to genetics rather than shared environment

Question 5

brendegen’s conclusions?

Answer 5

• moderate overlap in social / physical aggression
• physical: 50-60% genes / the rest non-shared environmental
• social: 20% genes / 60% non-shared environmental
• children must be from physical to social aggression as they age