Brendgen

• Aim

  • Social aggression caused by genes or environment​
  • Social aggression has same cause as physical agg​
  • One type of aggression leads to another​
• Procedure Pt1

  • 234 twin pairs from Quebec born between 1995 and 1998.
  • Data collected longitudinally at 5, 18, 30, 48 and 60 months, then at 6 years​
  • Data collected was 2 ratings of each twins behaviour by teacher + classmates.​
  • Written consent by all parents​
• Procedure Pt 2

  • Teachers ratings were a series of statements on physical and social aggression e.g. to what extent does your child try to make others dislike a child (social)/get into fights (physical)',  from the Preschool Social Behaviour Scale, from 0 to 3 (0 – never, 3 – often)​
  • Peer ratings by kids circling pics of child fitting description e.g. gets into fights, tells other not to play with a child.​
  • Each child given a social/physical score based on teacher rating and peer rating was recorded​
• Findings

  • Boys more physically aggressive, girls more socially​
  • Higher correlation with MZ than DZ overall​
  • MZ correlation double than DZ with physical​
  • MZ correlation similar to DZ with social​
• Conclusion

  • Strong genetic component to physical aggression, but not social (which is due to environment)​
  • More physically aggressive tend to be more socially aggressive – due to an interaction between environmental factors + genes​
  • Become more socially aggressive with age – social conventions on physical violence​
• :) Objective

  2 different sources of info on physical + social behaviour from..., eliminate bias. T/f data is objective so increases internal validity of...​
• :) Informed Consent

  Brendgen got written consent from the parents of the twins in the class before carrying out the study. T/f Brendgens study on...is ethical​
• :( Demand Characteristics

  The teachers/peers may have guessed that the true aim of the study was...and rated the children more or less aggressive than they are. T/f the data is unreliable and could be inaccurate, reducing internal validity​
• :( Population Validity

  all ppants were from the Quebec New Born Twin Study and born between 1995-1998. T/f results on...cant be generalised to a wider pop​