Examining genetic and environmental effects on social aggression: A study of 6 year old twins.
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 type.
- Sample: Participants were recruited from the Quebec Newborn Twin Study (QNTS) and were all pairs of twins born between November 1995 and July 1998. 322 pairs were tested but complete data from all stages was only gathered in 234 pairs. Of the 234 pairs, 44 were MZ males, 50 were MZ females, 41 DZ males, 32 DZ females and 67 DZ mixed.
- Data: Data was gathered longitudinally at 5, 15, 30, 48 and 60 months and then again at 6 years.The data consisted of two ratings of each twin's behaviour, one by their teacher and one by their classmates. Ratings were gathered in the Spring term of the school year to ensure the twins were well known.
- Teacher ratings: Based on agreement with a series of statements taken from behaviour scales, eg 'to what extent does the child try to make others dislike a…