Brendgen

Brendgen

1. AIM

   • Find out if there was a difference in physical and social aggression in 6 year old school by surveying their teachers and classmates
   • If physically aggressive children are also socially aggression and the link to genetics through comparing MZ and DZ twins

2. IV

   • 1) Aggression scores between MZ twins
     • 2) Aggression score between DZ twins
       • 3) Teachers rating for aggression of children
         • 4) peer ratings from classmates of children's aggression

3. DV

   • Teachers ratings out of physical and social aggressions were calculated out of 6 each
     • Classmates asked to identify their classmates from photographs of various descriptions

4. SAMPLE

   • 234 pairs of twins from Quebec newborn twin study
   • Longitudinal study - Brendgen used data from age 6
   • 44 sets of identical MZ male twins and 50 sets of identical female MZ twins
   • 41 sets of non-identical DZ twins and 32 sets of non-identical DZ twins
     • 67 sets of mixed gender non-identical twins

5. PROCEDURE

   • Children entered into QNTS when they were born and assigned to MZ or DZ depending on physical appearance
     • 123 pairs of twins DNA-tested, backed up assignment to MZ and DZ twins 94%, reliable
       • By age 6, 88 pairs of twins had dropped out.234 [pairs of twins left
         • Parent's consent obtained and permission from schools
           • Some schools were english-speaking and some french, researcher had to speak both language and surveys translated
             • Teachers asked to rate children on a 3 point scale. ( 0- never, 1- sometimes, 3- often) on 6 statements
               • 1)tries to make other dislike a child
                 • 2) says bad things or spread rumorus of another child
                   • 3) becomes friends with another child for revenge
                     • 4) gets into fight
                       • 5) Physically attacks others
                         • 6) HIts, bites or kicks others
                           • 2 scores for physical and social aggression were added together to produce two oevrall scores
               • The children were given easier task, asked to circle photos of 3 children who fit these 4 descriptions
                 • 1) tells others not to play with a child
                   • tells mean secrets about another child
                     • gets into fights
                       • its, bites or kicks others

6. RESULTS

   • Chi squared inferential test- comparing teacher and peer ratings. Differences were not significant
     • Teacher and peer ratings were in correlation making the results more valid as they were in agreement
       • Teachers rated boys more physicaly aggressive and girls more socially. Peers rated boys to be both
         • MZ correlation for physical aggression were twice as high than DZ twins
           • This suggests MZ have similar behaviour in both physical and social aggresion
             • MZ and DZ correlation for social aggresion were similar. This suggests social aggresion has less to do with genetics.
               • DZ twins are more influenced by their surroundings
                 • Little disagreement with MZ physically agression but more with DZ

7. CONCLUSIONS

   • 50-60% of physical aggression can be linked to genes and 20% of social aggression to genes
   • non-shared environemt. 40% of physical aggression , 60% of social aggression
   • 20% of social aggression to shared environment
   • Physical aggression is mostly nature (genes) and social aggression is mostly nurture

8. GENERALISABILITY

   • Large sample. Anomalies averaged out. Sample is representative
   • Researchers think sample too small, if replicated they should use larger samples
   • Not generalisable to non-twins

9. RELIABILITY

   • Used established questionnaires. Can be easily replicated
   • Inter-rater reliability- two researchers visited each classroom
   • Strong correlation between teacher and peer ratings
   • Language may make it less reliable. Different meanings in questions

10. APPLICATION

    • If social aggression is linked to environment, can reduce the effects of verbal abuse, gossiping and trolling on social media.
      • Classes and workshops to help children interact in less aggressive ways
    • Parenting skills

11. VALIDITY

    • Valid way of testing nature vs nurture
    • Cannot show cause and effect
    • Avoid taking reductionist view of human behaviour

12. ETHICS

    • Presumptive consent given by responsible adult
      • Risk for children who participated as bullying could get bad
    • Bad impacts on friendships
    • Social responsibility- for the greater good