Valid and reliable teacher ratings serve as the foundation for screening and assessment of youth with behavioral disorders and twin studies offer an opportunity to study those ratings. We conducted a meta-analysis of 15 empirical investigations of aggressive and rule-breaking behavior using teacher ratings in the context of a twin research design.…

The non-cognitive skills self-control and grit are often considered predictors of school performance, but whether this relationship is causal remains unclear. We investigated the causality of this association using a twin design. Specifically, we evaluated the direct impact of self-control and grit on school performance, while controlling for…

The present study examined, within a longitudinal family-informed design and across middle childhood, the predictive associations between preference for solitude and social wariness, two forms of social withdrawal, and peer difficulties. Specifically, preference for solitude, rather than social wariness, was expected to predict peer victimization…

Using a sample of 767 children (403 girls, 364 boys), this study aimed to (a) identify groups with distinct trajectories of peer victimization over a 6-year period from primary school through the transition to secondary school, and (b) examine the associated personal (i.e., aggression or internalizing problems) and familial (family status,…

This study used the monozygotic (MZ) twin difference method to examine whether differences in friends' aggression increased the differences in MZ twins' aggression and depressive symptoms from kindergarten to Grade 1 and whether perceived victimization by the friend played a mediating role in this context. Participants were 223 MZ twin pairs.…

With a sample of 242 twins (135 girls, 107 boys) studied longitudinally, behavioral inhibition (BI) and inhibitory control (IC) measured at 3 years, as well as early and concurrent family process variables, were examined as predictors of shyness and of anxiety symptoms approximately 4 years later. Structured observational data from laboratory and…

Impulsivity and inattention are key constructs at the interface of temperament and domains of childhood behavioral problems, such as ADHD and ODD. A multi-method, multi-source assessment of impulsivity and inattention was conducted with 256 families of twins at a mean age of 8-9 years from an epidemiologically defined community sample. Analysis of…