The Montreal Longitudinal and Experimental Study (MLES) began in 1984. The original aim was to study the development of antisocial behavior from kindergarten to high school with a specific focus on the role of parent-child interactions. To that purpose we assessed all the kindergarten boys in 53 schools of low socioeconomic areas in Montreal, to identify those who were most disruptive, and to intensively study the parent-child social interactions of a subset of them until high school.
In the spring of 1984, the kindergarten teachers of each of the 53 schools in the low socioeconomic areas of Montreal were asked to rate the behavior of each of their male students. Teachers typically had a morning and an afternoon group, each consisting of approximately 8 boys and 8 girls. Ratings were returned by 87% of the teachers, and 1,161 boys were rated. The next step involved identifying those who were the most disruptive. First, to control for cultural effects, we included in the longitudinal study only the boys with biological parents who were born in Canada and whose mother tongue was French (n = 1,038) and who were not older than 81 months when they finished their kindergarten year. After applying these criteria and eliminating families who refused to participate further in the study (n = 1), 1,037 boys remained. We then used 13 items of the Preschool Behavior Questionnaire (Tremblay, Desmarais-Gervais, Gagnon, & Charlebois, 1987; Tremblay et al., 1991) in order to identify the most disruptive boys: Bullies; kicks, bites, hits; fights; disobedient; blames others; irritable; destroys things; restless; inconsiderate; tells lies; squirmy; doesn’t share; not liked.
A sub-sample of disruptive boys was created by selecting those above the 70th percentile of the disruptive behavior scale from teacher ratings. Three groups of disruptive kindergarten boys were randomly created (total N=250): An intensive longitudinal observation group (Group A), an experimental intervention group (group B) and a third group of subjects which would be assessed yearly and would thus serve as a control group (Group C) for the intervention, as well as a control group for the possible effects of the intensive longitudinal observations of group A. From this perspective Group A was also an attention-control group for the experimental group (Group B).
The financial resources for this large-scale data collection became available in time to assess all the boys when the majority of them were finishing Grade 4, and turning ten years of age.
When in kindergarten, the majority of the boys lived with both their biological parents (67%), but one out of four (24%) was living alone with his mother, and 5% were living with their mothers and a man who was not the boy's father; the rest (4%) were living in other family arrangements (e.g., with grand-parents, with father and stepmother). Parents' mean age at the birth of their son was 25.4 (SD = 4.8) for mothers, and 28.4 (SD = 5.6) for fathers. This varied from 15 to 45 years for mothers, and from 16 to 56 years for fathers. The mean number of school years completed by the mothers was 10.5 (SD = 2.8), and 10.7 (SD = 3.2) for fathers. The majority of the parents were unskilled workers. The mean score on the Canadian socioeconomic index for occupations (Blishen, Carroll, & Moore, 1987) was 38.15 for mothers and 39.19 for fathers. This index ranges from 17.81 for the lowest status to 101.74 for the highest status, with a mean of 42.74 (SD = 13.28). The mean and median family income when the boys were age 10 years (1988) was between $25,000 and $30,000 (Canadian dollars; $19,000 to $23,000 in US dollars) compared with a median income of $44,000 (Canadian dollars) for couples with children in Canada in 1987 (Mitchell, 1991).
The main instruments used in the MLES to assess behavior problems are mother and teacher ratings and self-reported delinquency. Behavior ratings were also obtained annually from mothers, and from classroom peers at ages 10, 11 and 12. A structured psychiatric interview was conducted with the boys and their mothers when the boys were 15 years of age. Annual questionnaires completed by mothers provided information on family background, life events, parenting behavior, domestic relationships, and social support. Annual interviews with the boys provided information on a variety of dimensions including personality, life events, perceptions of parenting, domestic relationships, friendships, attitudes toward school and the law, sleep substance use and leisure activities. Direct observations of social interactions were made at school, at home and in laboratory situations with sub-samples between ages 7 and 15. Psychophysiological and as different biological assessments, were also made on sub-samples between age 7 and 20. Involvement in criminal activities and high school dropout status were obtained from official records by the end of adolescence and again during early adulthood. Finally, information about employment and marital status, income and social welfare receipts were obtained through Statistics Canada from ages 20 through age 37.
Teachers and mothers rated the boys' behavior in the spring, from age 6, at the end of the kindergarten year, to age 15. The six scales derived from teacher and mother ratings were: Physical aggression (fights with other children; kicks, bites, or hits other children; bullies or intimidates other children); Opposition (doesn't share materials; irritable; disobedient; blames others; inconsiderate); Covert conduct problems (destroys property, lies, steals, truants), Anxiety (tends to be fearful or afraid of new things or new situations; cries easily; appears miserable, unhappy, fearful, or distressed); Inattention (has poor concentration or short attention span; inattentive); Hyperactivity (restless, runs about or jumps up and down, does not keep still; squirmy, fidgety); and Prosocial behavior (comforts upset child; helps sick child; helps hurt child; praises other; helps with task difficulty; helps clear up mess; shows sympathy; invites bystander; stops quarrels; helps pick up objects). Teachers and mothers also reported on the children’s school performance using a rating scale.
Self-reported delinquency was assessed every year from ages 10 to 17 and around age 20. The boys were seen in small groups at their schools between March and May; they answered 27 self-reported delinquency items which were distributed in a questionnaire pertaining to school, family, friends, and leisure activities. The items were: steal from school; steal from store; steal from home; keep object worth less than $10; steal bicycle; sell stolen goods; keep object worth between $10 and $100; steal objects worth more than $100; breaking and entering; enter without paying; trespassing; take drugs; take alcohol; get drunk; destroy school material; destroy other material; vandalism at school; destroy objects at home; vandalize car; set a fire; strong-arm; gang fights; use weapon in a fight; fist fight; beat up someone; carry a weapon; throw objects at persons. The responses to all 27 items ranged from 1 (never) to 4 (very often).
The Intervention included two major components (a parent training program based on techniques developed at the Oregon Social Learning Center and a classroom-based social skills program for the children). In brief, the parent training component involved: (1) giving parents a reading program; (2) training parents to monitor their children’s behavior; (3) training parents to give positive reinforcement for prosocial behavior; (4) training parents to manage family crises; (5) use of non-abusive punishments for the child’s behavior problems; and (6) helping parents to generalize what they have learned. The parent training component was supplemented by eliciting cooperation from the teacher. Work with parents and teachers was carried out by two university-trained child-care workers, one psychologist, and one social worker, all working full-time. Each of these professionals had a caseload of 12 families. The team was coordinated by a fifth professional who worked on the project half-time. Work with the parents was planned to last for 2 school years with one session every 2 weeks. The professionals were, however, free to decide that a given family needed more or fewer sessions at any given time. The maximum number of sessions given to any family was 46 and the mean number of sessions over the 2 years was 17.4, counting families that refused to continue.
For the school based social skills training component of our interventions, two types of training were given to the disruptive boys within a small group of prosocial peers in school. During the first year a prosocial skills program was devised based on other programs (Cartledge & Milburn, 1980; Michelson, Sugai, Wood, & Kazdin, 1983; Schneider & Byrne, 1987). Nine sessions were given on themes such as “How to make contact,” “How to help,” “How to ask ‘why’,” and “How to invite someone in a group.” Coaching, peer modeling, role playing, and reinforcement contingencies were used during these sessions. During the second year the program aimed at self-control. Using material from previous studies (Camp, Blom, Hebert, & Van Doorminck, 1977; Goldstein, Sprafkin, Gershaw, & Klein, 1980; Kettlewell & Kausch, 1983; Meichenbaum, 1977), 10 sessions were developed on themes such as “Look and listen,” “Following rules,” ‘What to do when I am angry,” “What to do when they do not want me to play with them,” and “How to react to teasing.” Coaching, peer modeling, self-instructions, behavior rehearsal, and reinforcement contingencies were also used during these sessions. This component too was offered by the professionals who provided parental training, although different workers assisted the parents and the child.