Models for Developmental Trajectories: An Application to the Development of Conduct Problems

Alan Taylor, Institute of Psychiatry
Daniel S. Nagin, Carnegie Mellon University
Terrie E. Moffitt, Kings College London
Avshalom Caspi, Kings College London

ABSTRACT
Theories of development in psychology often posit the existence of sub-groups which follow distinct developmental profiles or trajectories. For example, Moffitt (1993), has proposed that antisocial conduct problems, such as fighting, bullying and criminal activities, show three primary developmental trajectories from early childhood to middle life. Along with a large group who consistently show low levels of antisocial behaviors, Moffitt proposed the existence of two groups who show high levels of antisocial behaviour: a "life-course persistent" group and an "adolescent limited" group. We use the methods introduced to psychology by Nagin (1999) which apply a mixture model approach to developmental trajectories to investigate the validity of this theory using data from the Dunedin Multi-disciplinary Cohort Study (Silva & Stanton, 1996). The Dunedin Study provides repeated measurements from age 7 to 26 on a cohort of approxdimately 1000 individuals and has multiple data collection instruments. Model fitting indicated that the theory of Moffitt (1993) was validated in this data as the hypothesised population groups and their trajectory profiles were found in the best fitting model. Further more, the relationship of the trajectory groups with other measures through the life-span gave further credibility to the groups found using the mixture model approach.

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Updated 05/20/2006