brengden

• aims


  to investigate aggression in MZ and DZ twins to find:

  - the extent social and physical aggression is explained by genetic and environmental influences

  - whether the overlap between social and physical aggression is explained by direct effect of one type of aggression on the other
• method


  twin study used, correlation study, 234 pairs of twins from QNTS
• procedure


  rating taken:

  1) teacher ratings - rated the social and physical aggression of each child on a 3 point scale in response to questions

  2) peer ratings - classmates ranked aggression through a book of photos, pointed to three children who best fit a description of a behaviour

  . correlation test carried out
• results


  - higher correlation between MZ pairs in physical aggression than DZ pairs in both ratings

  - social aggression roughly equally correlated in both

  - teachers rated boys more physically and girls more socially

  - peers rated boys both more
• conclusion


  - strong genetic component to physical aggression, social is more due to environmental factors

  - physical aggression may lead to social aggression but not the other way round
• evaluation - generalisability strength

  large sample size 234 twins = aggression can be measured in a range of children in target population
• generalisability CA


  age group of 6 yeasr old = specific so can't assume aggression would be same in other ages

  conducted in quebec = individualistic culture = aggression may be showed more/may be more overt

  so cant generalise to wider population and apply results to others
• generalisability so what


  although sample is large, the specific age group and culture means findings aren't representative of wider population so can't be applied to them = bad generalisability
• reliability strength


  strong due to standardised measures of aggression ratings eg rating scales and descriptive ratings = consistency in measurement
• reliability CA


  may have been differences in how individuals interpreted the scales so some subjectivity = lowers reliability
• reliability so what


  however there is high internal reliability which means replication is possible = good reliability
• applications


  - help understand gender differences in aggression = lead to support for boys eg channeling aggression through sports

  - can prevent development of social aggression as intervention can happen when physical aggression seen to prevent its development
• validity strength


  - measures taken from 2 sources (teachers and peers) and the data matched = views weren't biased = increases validity

  - care was taken to keep semantic meaning of questions the same in both languages = language was not an extraneous variable
• validity CA


  the measures of aggression may be hard to operationalise = lack of validity

  - twins shared the same environment = difficulty to establish cause and effect between environmental impacts and genetics
• validity so what


  overall strength as there is good internal validity and extraneous variables were controlled meaning study is valid despite the fact conclusions may be hard to come to
• ethics weaknesses


  - peer ratings = labelling children as aggressive = could compromise children and raise protection from harm issues

  - socially sensitive = concluded aggression is genetic = can create labels and self-fulfilling prophecy by identifying a 6 year old as genetically aggressive
• ethics strength


  parental consent gained = competency in using guidelines demonstrated