Brendgen 2005 twins

• What were the 3 aims for this study?

  1.To see if social aggression could be Caused by genes or the environment

  2.To see if social aggression shared the same cause as physical aggression

  3.To see if one type of aggression leads to another
• Where were the participants recruited from?

  Quebec Newborn Twin Study
• When were all the twins born between?

  November 1995 and July 1998
• How many pairs of twins were tested at the start of the study?

  322
• How many pairs of twins had complete data gathered on them?

  234
• How many pairs were MZ males?

  44
• How many pairs were MZ females?

  50
• How many pairs were DZ males?

  41
• How many pairs were DZ females?

  32
• How many pairs were mixed sex DZ?

  67
• How was the data gathered?

  longitudinally
• What were the months where data was gathered?

  5, 18, 30, 48, 60
• How old were the twins at the last data collection?

  6 years
• Who rated the behaviour of the twins?

  Teachers and peers
• What were the teacher ratings based on an agreement from?

  A series of statements from items on the Preschool Social Behaviour Scale and the Direct and Indirect Aggression scales.
• How were the peer ratings taken?

  each child in the twins’ classes were given a booklet containing photos of every child in the class, they were asked to circle 3 pictures of children they thought matched the 4 behaviour descriptions
• In the results, which type of twins had a higher correlation on physical aggression?

  MZ had a higher correlation on physical aggression than same sex DZ twins did
• What type of aggression was roughly equal between MZ and DZ twins?

  Social aggression
• What do the findings suggest?

  physical aggression may be caused by genetic factors whereas social aggression may be better explained by shared environmental factors
• For the second aim of the study, what were the results relating to it?

  a correlation was found between physical and social aggression children and this is best explained by genetics rather than the same environment
• In relation to the third aim of the study, what were the results?

  Physical aggression may lead to social aggression
• What did Brendgen conclude?

  Expression of aggression changes as children grow and learn more socially acceptable ways of showing aggression.

  There is a strong connection between genetics and physical aggression but not social aggression.

  Children who were more physically aggressive tend to be more socially aggressive
• Which 2 of the following are strengths of the study?

  1.generalisability

  2.inter rate reliability

  3.usefulness

  4.extraneous variables

  1.Inter rate reliability- two different sources were used, teachers and peers. This means that the validity is increased and bias is minimised. The teachers were all in agreement which also suggests they were not biased. And there was consistency in the measurements which adds reliability

  2.Usefullness- this study has useful applications. They could be used to prevent development of social aggression and if it is seen early, putting practices in place early can prevent it from developing.
• Which 2 of the following are weaknesses of the study?

  1.Reductionist

  2.Generalisability

  3.Extraneous Variables

  4.Eco-logical validity

  1.Generalisability- they had a small sample size when it comes to all the different groups being compared. This means generalisation is difficult because the chance of the results being representative of a population is low. They also used a specific age group which means the results cannot be generalised to other ages.

  2.Extraneous Variables- there could've been extraneous variables in the lives of the children that Brendgen couldn’t control which may explain some aggression.