Contemporary study ;Brendgen Et Al

1)see if social agg was caused by genes or env 2)see if social agg shared same cause as physical agg 3)see if one type of agg leads to another

-234 pairs of twins -44 sets of MZ male -50 sets of MZ female -41 DZ males(non identical) -32 DZ females (non identical) -67 DZ mixed gender twins

-Quebec Newborn study whcih was a longitudinal study that was already going on -Brendgen used the data from it when the children were 6 -because the sample was taken from another study, this is cluster sampling

1-children entered the Quebec Newborn Twin study when they were born and were assigned to MZ or DZ based on their physical resemblence 2-by age 6, 88 pairs of twin dropped out the study however she still had a sample of 234 3-she got written consent from parents and approached their schools 4-some schools were english speaking and some french so the surveys had to be translated and researchers had to speak both languages

teachers were given questionnaires where they had to rate each child on a 3 point scale with how often they did these statements -0 was for never, 1 was sometimes, 2 was often -there were 6 statements including things like ‘gets into fights’, ‘physcially attacks others’ ‘tries to make others dislike a child’ -three for social agg and 3 for physical -scores for each aggression added up to produce two overall scores

-used a chi squared to compare the teacher and peer ratings for each aggression and found the differences were not significant so combined the ratings (increases inter rater reliability) -found strong correlation between teacher and peer ratings suggesting agreement -correlation for PA: 0.25 -correlation for SA:0.33

-shown photos of their classmates and asked to circle the photos of 3 children who best fit the 4 descriptions which were 2 for social agg and 2 for physcal: -tells others not to play with a child -tells mean secrets about another child -gets into fights -hit, bites or kicks others

MZ=0.61,DZ=0.25

MZ=0.36,DZ=0.34

-that physical agg was better explained by genetics and social agg by env -physical agg can lead to social agg but not the other way -agg tendencies may be more likely to show as learn more socially acceptable ways to be agg -is someone is physically agg then likely to also be socially agg

-teachers rated boys more physically aggressive, girls more socially aggressive however peer ratings showed boys as more aggressive in both categories

-MZ correlations for phsycial aggression were twice as high as same sex DZ twins: r=0.79 for MZ twins suggested that MZ twin behaviours were very similar suggesting genetic influence for PA and environmental for SA

-MZ and DZ correlations for SA were similar suggesting that social aggression is less linked to genetics

-about 50-60% of PA can be linked to genes as it was shared more by MZ than DZ twins -for social agg, genes only accounted for around 20% -considered ‘non-shared environment’ as an influence too which includes things like friends etc -linked 20% of SA to ‘shared environment’ so things like parenting strategies ie if the parent control the child with love and affecting, they will do the same in their friendships -Brendgen proposed that genes may give children a general predisposition towards aggression but this only becomes social agg if their env encourages it

-large smaple meant that any anomlaies would be averaged out -88 twins dropped out: potentially there was something different about them, may have been more disturbed or from chaotic backgrounds -tendency for people to drop out=sample atrittion -only using 6 year olds means there could be differences in maturity:more mature children may have more non-shared environmental influences (they do more things away from home).

-standardised proc and use of standardised questionnaires=easy to replicate and inc reliability -two researchers visited each classroom inc inter-rater reliability -strong correlation between teacher and student results=reliable -translation from french to eng may have had errors=unreliable -allocation of MZ and DZ categories was based on appearance so may not have been 100% accurate

-ratings may have been subjective depending on twins relationship with a classmate or teacher

-MZ twins were guessed by visuals -one twin may be stereotyped to a certain behaviour meaning both get a bad reputation and so given the same scores or mistaken for the other -correlation does not imply causation as something else could be affecting the MZ twins

-gained written consent -limited protection from psychological harm by getting the children to look at pics of each other and choose, they may gossip about who they chose for what which goes against social responsibility of ethical research and may raise risks