ABSTRACT
This chapter examines separately individual factors defining trajectories of behaviours leading to delinquency and substance use in boys, and environmental factors related to such trajectories. It describes research from the Montreal Longitudinal-Experimental Study (MLES). The MLES is based on a population of boys from low socioeconomic status families in Montreal, Quebec, followed up from kindergarten to early adulthood. Different strategies were used to examine developmental trajectories of individual behaviour related to antisocial problems and delinquency. The stability of antisocial behaviour from kindergarten to the end of elementary school was established. Research strategy consisted of creating behaviour profiles, a 'person approach', rather than a 'variable approach' based on association between different measures, to study the development of antisocial behaviour. Making the best of yearly measures of MLES, D. Nagin and R. E. Tremblay have used a method proposed by Nagin and Land to establish developmental trajectories of aggression, opposition and hyperactivity on the path to juvenile delinquency.
