Contemporary Study: Brendgen (2005)

Contemporary Study: Brendgen (2005)

1. Generalisability

   • The study used a large sample with mixed genders. This makes results more generalisable as the sample is more representative of the population.
     • 234 sets of twins. The sample consisted of 44x male Mz twins, 50x female Mz twins, 41x male Dz twins, 32x female Dz twins and 67x mixed gender Dz twins.
   • HOWEVER all twins came from the same institution which limits the generalisability beyond Quebec/Canada to other cultures.
     • The sample was taken from the Quebec Newborn Twin Studies institution.

2. Reliability

   • Two researchers visited each classroom which increases the inter-rater reliability of the results.
   • There is high reliability in the results as data was gather via two tests (teacher ratings and peer data), both of which found the same results.
     • Data was also gathered through collecting teacher rating on each child. Teachers were given the same 6 statements (control), such as "Hits, kicks and bites people" and "Spreads nasty rumours about others" and were asked to rate the child on whether they "often" did those things, "sometimes" did those things, or "never" did those things. A score was then worked out for both social aggression and physical aggression.
   • Twins were determined to be either Mz twins or Dz twins purely based on looks. This is not a reliable method of grouping participants and some twins may have been in the wrong group, in particular Dz twins could have been mistaken as Mz twins based on looking similar when in reality they were not 100% identical.
   • Reliability could also be affected by the language differences. This is because translation may be required, which could make things confusing and inaccurate and affects results.

3. Application

   • Early intervention could be used in order to help families and prevent social aggression.
     • Aimed to find out the origins of social aggression (e.g. ignoring people, spreading rumours...). Brendgen wanted to see if social aggression was genetic or environmental, if the cause of physical aggression was the same as the cause of social aggression, and if physical aggression/social aggression leads to one another.
     • Brendgen found that there was a link between social aggression and the environment.

4. Validity

   • As the study was a natural experiment and correlational data was gathered, cause and effect cannot be gained. This reduces the validity of the results.
     • There was a high correlation found between Mz twins and physical aggression, suggesting physical aggression is due to nature.
     • The correlation between Mz and Dz twins and social aggression was roughly equal, suggesting social aggression is due to nurture.
     • There was a correlation found in Mz twins between social aggression and physical aggression, and it was suggested that physical aggression leads to social aggression: aggression tendencies change as you grow up from physical aggression to other ways of demonstrating it (longitudinal study).
   • Other factors may have influences the scores being given by teachers and peers. For example, stereotypes about twins might have influenced teachers and peers and therefore they may have scored both twins the same, despite any behavioural differences there may be in reality. This could affect the validity of the results as they may not reflect actual behaviours.

5. Ethics

   • The study could have caused potential conflict within friendships and amongst the children and their peers if they found out who their peers selected in each category.
     • One way Brendgen collected data was through peer ratings. Classmates were given a phonebook of the class and asked to circle three photos of the people who they believed the statements read out best fit. Statements were along the lines of "Gets into fights" and "Tells other children not to play with a child". A social aggression score and physical aggression score was then calculated for each participant.
   • Only gained presumptive consent, and as the participants were young children, they could not give their own consent.