Brendgen et al

Question 1

aims

Answer 1

• investigate the extent to which social and physical aggression are explained by genetic and environmental influences
• whether the overlap between social and physical aggression is explained by the direct effect of one type of aggression on another

Question 2

sample

Answer 2

-234 pairs of twins were selected from longitudinal Quebec Newborn twin study (QNTS)
- QNTS collected data from the twins regularly beginning at 5 months to 6yrs old

• in final analysis :
  44 male mz twins
  50 female mz twins
  41 male dz twins
  32 female dz twins

Question 3

procedure (first half = teachers)

Answer 3

• kindergarten teacher rated social and physical aggression of each child in a 3 point scale (never sometimes often) in response to social and physical aggression

Question 4

give an example of a social item used in the 3 point scale

Answer 4

“says bad things”

Question 5

give an example of physical item on the 3 point scale

Answer 5

“hits, bites and kicks others”

Question 6

procedure (second half - peer )

Answer 6

• levels of twins social and physical aggression were rated by their classmates
• classmates were given a booklet of photographs of all the children in their class and were asked to nominate the 3 children who best matched a description of behavior for each page
• there were 2 descriptions for social and physical behavior each

Question 7

what did the researcher check before the peer procedure to ensure results were valid

Answer 7

• that each child could recognize everyone in their class

Question 8

give an example of a description of social aggression the children were given

Answer 8

“tells others not to play with a child”

Question 9

give an example of a description of physical aggression the children were given

Answer 9

“gets into fights”

Question 10

findings

Answer 10

• only 20% to 23% of social aggression were explained by genetic factors
• physical aggression was mainly explained by heritable factors and partly shared environmental influences
• social aggression was mostly explained by non shared environmental factors
• a correlation between social and physical aggression explained by overlapping genetic influences

Question 11

conclusion

Answer 11

• genetic characteristics predispose children to aggressive behavior in general
• modelling indicated that the specific form of the aggression it takes is more influenced by environmental factors which are different for social and physical aggression
• directional relationship between social and physical aggression is explained by developmental processes
• as children grow they become more socially aggressive because of social conventions on physical violence and develop different ways to express themselves

Question 12

generalizability strengths

Answer 12

• large sample size (234 pairs of twins) = representative of population

Question 13

generalizability weaknesses

Answer 13

• sample attrition = 88 pairs of twins dropped out before the study ended
• these could have included disturbed children with unusual backgrounds = not representative of people like that
• only studied children / 6 year olds

Question 14

reliability strengths

Answer 14

• multiple data sources from teachers and peers which were very similar providing reassurance that the measure was accurate
• used questionnaires to measure = standardized and easy to replicate

Question 15

weaknesses reliability

Answer 15

• questionnaire was translated from french to english, these translations weren’t 100% accurate and some things may have been translated into slightly different things, which could affect results
• allocation of zygocity was mainly down to appearance - not 100% accurate

Question 16

application strengths

Answer 16

• if social aggression is linked to the environment it may be possible to decreased verbal bullying,gossiping by using early intervention
• if friends and family are a big influence it suggests by educating parents to be better role models it may prevent children being aggressive

Question 17

validity strengths

Answer 17

• good way of studying nature vs nurture
• high ecological validity
• avoids reductionist view

Question 18

validity weakness

Answer 18

• based on equal environments assumption which may be wrong as parents of dz twins may behave more aggressively towards 1 child = undermined validity

Question 19

ethics strengths

Answer 19

• presumptive consent given
• development of social aggression can be used to maximize benefit of all children

Question 20

ethics weaknesses

Answer 20

• may go against social responsibility as it could have a bad impact in friendships of children if they found out who selected who

Question 21

physical aggression

Answer 21

behavior that threatens to cause physical harm to others / environment

Question 22

social environment

Answer 22

a behavior that harms a persons social status/ relationships

Question 23

shared environment

Answer 23

environmental factors which make family members more similar to each other

Question 24

non shared environment

Answer 24

• any environmental factors that makes twins different, unique experience which individuals don’t share

Question 25

ACE model

Answer 25

estimates heritability to see how much variation on a phenotype is due to genetic effects, common environment and unique environment

Question 26

equal environments assumption

Answer 26

idea that mz and dz twins experience equally similar environments

Question 27

sample attrition

Answer 27

when participants drop out of a study before it ends