A person-oriented approach was adopted to examine joint developmental
trajectories of physical and indirect aggression. Participants were 1183
children aged 2 years at the initial assessment and followed over 6 years.
Most children followed either low or declining trajectories of physical
aggression (PA), but 14.6% followed high stable trajectories.
Approximately two-thirds of participants followed low indirect aggression
(IA) trajectories (67.9%), and one-third (32.1%) followed high rising
trajectories. The results combining both PA and IA group memberships
indicate that most children (62.1%) exhibit desisting levels of PA and low
levels of IA. A significant proportion followed a trajectory of moderately
desisting PA and rising IA (14.2%), and 13.5% followed high level
trajectories of both forms of aggression. Virtually no children were high
on one type and low on the other. Multinomial regressions analyses were
used to predict joint trajectory group membership from selected child and
family variables measured at 2 years. Young motherhood and low income
predicted membership in the high PA-high IA trajectory, but only hostile
parenting remained significant after family processes variables were
entered in the model. Being a boy, young motherhood, and hostile parenting
were generally associated with higher levels of PA. Girls were more likely
than boys to follow a trajectory of desisting PA and rising IA. The
results suggest that some children, mostly girls, reduce their use of PA
and tend to increase their use of IA, and that highly physically
aggressive children also tend to be highly indirectly aggressive. Early
family risk characteristics and hostile parenting interfere with the
socialization of aggression.This research
was supported by research grants from Quebec's FQRSC and CIQSS,
Canada's CIHR and SSHRC, the Canadian Institute for Advanced
Research, the Molson foundation, St-Justine Hospital's Research
Center, and the University of Montréal. We thank Danielle Forest
(University of Montréal) for her work on data analysis and Franck
Larouche (Statistics Canada) for his sustained commitment to assist us in
managing the data.