Contemp study brengen

• Aim

  • (causes of physical and social aggression if its from genes or environment)
  • to see if social aggression could be caused by genes or environment 
  • To see if social aggression shared the same causes as physical aggression 
  • To see how aggression develops and if one type of aggression leads to another - if physical aggression leads to social aggression 
• 1. Opportunity sample:

  • selection of 6 year old twins from Quebec newborn twin study , greater Montreal area
  • Used 234 twin pairs: 44 MZ male, 50 MZ female, 41 DZ male, 32 DZ female and 67 DZ mixed gender
  • Physical resemblance at 18 months was used to allocate MZ/DZ category.  DNA was only tested in 123 pairs researchers were 94% accurate 
  • 84% European decent, 3% African decent, 2% native North American, 9% didn’t declare
  • Household income average was $54,000
• • written consent form obtained from all parents
  • Teacher and student ratings were obtained from 409 classrooms, 175 twin pairs were not in same class
  • Was approved by the institutional review board
  • Peer procedure took 45 minutes per class and were administered in either french or English 
  • Bilingual judges verified semantic similarity between translated questionnaires
  • Data was collected in spring of kindergarten so the children new each other 
• • Teachers rated each twin, Teachers completed behaviour questionnaires where they rated the child’s social and physical aggression using standardised scales never/sometimes/often) which gave each child a social aggression score and a physical aggression score.
  • children were asked just to rate top 3 most aggressive in class - Peers were asked to circle photographs in response to instructions i.e. pick the three who best fit the behaviour. Each child received a total social aggression score and a total physical aggression score.
• Results

  • Results physical aggression is 63% caused by genetic factors according to teacher rating, 54% according to children 
  • Social aggression is 60% caused by environment according to teacher rating, 54% according to children
• Conclusion 

  • physical aggression seems to be caused more by genetic factors and social aggression more by environmental factors
  • Individuals showing physical aggression did tend to show social aggression too. Possibly some children are predisposed by their genes to behave aggressively 
  • found a directional, effect- more physical aggression did tend to show social aggression to. Possibly some children are predisposed by genes to behave aggressively 
• Notes

  • Comparing how similar the results of the twins are, depending on if they have 100% the same genetics or 50%
• Strengths 

  • Reliability strength standardised procedure 
  • Generalisability strength Range of ethnicity’s, genders
  • Strength in ecological validity due to the classroom setting 
• Weakness

  • didn’t have a big enough sample of separate groups of boys and girls to understand if gender had a factor in aggression 
  • Validity weakness Self report may cause biased 
  • Validity weakness as the researchers were not 100% sure of the type of twin as they guessed
  • Generalisability Weakness as all children were 6