brendgen 2005

Question 1

background

Answer 1

• most of the research investigating the cause of aggression has focused on psychical explanations. this study is interested in the origins of social aggression.

Question 2

aims

Answer 2

the researchers were examining the genetic and environmental effects on social and psychical aggression using six year old twins.

• they wanted to investigate whether social aggression is caused by genes or the environment and to see if social aggression shared the same cause as psychical aggression. also to determine whether one type of agression led to another type.

Question 3

participants/ sample

Answer 3

• twins recruited from Quebec newborn twin study
• longitudinal study which followed twins at 5, 18, and 30 months and then at 4,5 and 6 years.
• at the start of study there were 322 pairs and of these 237 were same sex.
• they were assigned to identical or non identical categories based on psychical resemblance. 123 were DNA tested.

Question 4

procedure

Answer 4

By age 6, 88 pairs of twins had dropped out of the study, but Brendgen obtained data on the remaining 234 twin pairs, got written consent from the parents and approached their schools.

The teachers’ questionnaires asked them to rate each child on a 3-point scale (0 = never, 1 = sometimes, 2 = often) on these 6 statements:
tries to make others dislike a child
says bad things or spreads nasty rumors about another child
becomes friends with another child for revenge
gets into fights
physically attacks others
hits, bites or kicks others

The scores for social aggression and physical aggression were added together to produce two overall scores.

For the peer ratings, the children were given a simpler task. They were shown photos of their classmates and asked to circle the photos of 3 children who best fit these 4 descriptions:
tells others not to play with a child
tells mean secrets about another child
gets into fights
hits, bites or kicks others

Question 5

results

Answer 5

• a correlation using a chi squared test was performed on the results.
  the two sets of data were not significantly different from one another so the sets of ratings were combined together for the purposes of analysis.
• there were also reported gender differences in aggression
  according to teacher ratings: boys more psychically and girls socially
  according to peers:
  boys both

Question 6

conclusions

Answer 6

• physical aggression has a strong genetic component, whereas social aggression is a consequence of environmental factors. this suggests that psychical aggression may be due to the genes we inherit rather than environment. social seems to be influenced by environmental l factors.

Question 7

generalisability

Answer 7

• could be argued that the sample size was a strength 234 twins
• this allowed brendgen to measure social and psychical in a range of children in target pop.

CA- however the study was done in Quebec which is an indivualistuc culture where the aggression may be more covert in demonstrating social and psychical.

there are also issues with attrition eg 88 twins left. those lost may demonstrate different forms of aggression to those left in the sample. this may invalidate the study.

Question 8

reliability

Answer 8

:) the reliability of the study can be considered strong
eg there were stanardized measures of aggression ratings eg preschool behaviour rating scales and descriptive ratings for aggression for teachers.
this gives some consistency in how data was measured over time.

CA- however there could be differences in consistency of how the teachers used the scales as a result of between teacher differences.

Question 9

application

Answer 9

• understanding gender differences in aggression could lead to support for boys eg channeling it through sport.

Question 10

validity

Answer 10

• it could be argued that the study is valid as care was taken to ensure that the question asked had the same semantic meaning eg French and English
  this means that the study has a degree of construct validity.

CA that said there could be subjectivity in peer nominations and teacher ratings which could invalidate the findings
the teacher ratings may also differ from aggression from shown at home.therefore the study may not actually be accurately measuring aggression.

the zygoticity of the group can also be questioned eg psychical resemblance only.
this means that there could be issues with those classed as mz. therefore this could mean that mz twins may be wrongly classed as mz as they look similar. therefore impacting the overall validity of the psychical and social aggression findings.

CA - however a longitudinal method was used and therefore development of psychical and social aggression over time could be measured.

Question 11

ethics

Answer 11

• the study could be questioned in terms of ethics.
  eg peers circling children who fit aggressive descriptors
  this may therefore label some children and this could compromise the children and raise protection from harm issues.

however, parental consent was gained and so competency in using guidelines was demonstrated.