Brendgen et al (2005) A03

Question 1

Generalisability?

Answer 1

Strength - Brendgen uses a large sample (234 twin pairs), so unusual children (anomalies) with very high or low levels of aggression out to be “averaged out” by the size of the data. This makes the sample representative.

Question 2

Reliability?

Answer 2

Strength - The use of questionnaires to measure social and physical aggression is a reliable method, it can be replicated and is therefore consistent.

Question 3

Inter-rater reliability?

Answer 3

Strength - Two researchers visited each classroom which gives the study more reliability.

Question 4

Reliability - Weakness?

Answer 4

Weakness - The language differences might make the study less reliable. Questions translated into another language might have slightly different meanings or become confusing. Brendgen’s original questionnaires were in French, meaning the English translations might be unreliable.

Question 5

Reliability - Zygosity?

Answer 5

Weakness - The allocation of zygosity (MZ and DZ categories) was based largely on their appearance and wasn’t 100% reliable. In particular, it is possible there were DZ twins in the MZ condition.

Question 6

How can the results of this study help us in the real world (application)?

Answer 6

If social aggression is influenced by the environment then parents can be educated to be better role models and thus reduce the worst effects such as name calling and bullying.

Question 7

Validity - Stereotypes?

Answer 7

Something else could be affecting the MZ twins. For example, MZ twins tend to be physically identical and get mistaken for one another. It might be that one twin gets stereotyped based on the other twin’s behaviour (if one twin is naughty, both get a bad reputation).

In Brendgen’s study, teacher- and peer- ratings might have been influenced by stereotypes, with both children being given the same rating regardless of their behaviour.

Question 8

Ethics - Psychological Harm?

Answer 8

The study does get children to look at pictures of their classmates and judge them. This might have a bad impact on friendships, especially if the children told each other afterwards who they had selected as the “hitter and biter” or the “tale-bearer”.

Question 9

Validity - Multiple data sources

Answer 9

Strength - the researchers used ratings of aggression from two sources, teachers and peers).

The results from both sets of ratings were essentially the same.