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…

This study examined the moderating role of classroom injunctive norms salience regarding social withdrawal and regarding aggression in the longitudinal association between these behaviors and peer victimization. A total of 1,769 fourth through sixth graders (895 girls, M = 10.25 years, SD = 1.03) from 23 schools (67 classrooms) completed a peer…

This study examined the associations between intrinsic motivation and achievement in mathematics in a sample of 1,478 Canadian school-age children followed from Grades 1 to 4 (ages 7-10). Children self-reported their intrinsic motivation toward mathematics, whereas achievement was measured through direct assessment of mathematics abilities.…

This study used a genetically informed design to assess the effects of friends' and nonfriends' reticent and dominant behaviors on children's observed social reticence in a competitive situation. Potential gene-environment correlations (rGE) and gene-environment interactions (GxE) in the link between (a) friends' and…

Concurrent and longitudinal links between children's own and their nominated best friends' antisocial and prosocial behavior were studied in a normative sample of 3-5-year-olds (N = 203). Moderating effects of age and gender were also explored. Subscales of the Strength and Difficulties Questionnaire (SDQ) were used to obtain teacher ratings of…

Enriched environments may moderate the effect of genetic factors on prosocial leadership (gene-environment interaction, G × E). However, positive environmental experiences may also themselves be influenced by a genetic disposition for prosocial leadership (gene-environment correlation, rGE). Relating these processes to friendships, the present…

Using a genetically informed design, this study examined the additive and interactive effects of genetic risk, personal peer victimization experiences, and peer victimization experienced by others on children's aggression and depression symptoms. Of major interest was whether these effects varied depending on whether or not the victimized others…

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,…

Several authors consider high and frequent conflicts between friends during childhood as a serious risk for subsequent conduct problems such as generalized physical aggression toward others (e.g., Kupersmidt, Burchinal, & Patterson, 1995; Sebanc, 2003). Although it seems logical to assume that friendship conflict could have some negative…

This study used the monozygotic (MZ) twin difference method to examine whether the unique environmental effects of maternal and paternal overprotection and hostility at the age of 30 months predict twins' observed social reticence in a competitive situation in kindergarten, while controlling for the effect of family-wide influences, including…

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.…

This study had three goals: (a) assessing the predictive association of externalizing and internalizing behaviors during childhood with sexual onset during early adolescence; (b) examining the interactive link of externalizing and internalizing behaviors with early sexual onset; and (c) investigating the moderating effect of gender in this…

This study examined the longitudinal link between clique membership status and the development of psychopathology in 451 children followed annually from age 9 to 12 years. Classroom clique membership status was identified through social network analysis, and internalizing and externalizing problems were assessed using peer nominations. Controlling…

Background: Knowledge on the onset and the development of antisocial behavior in females is limited, because most of the research in this domain is based on males. Methods: We critically reviewed 46 empirical studies that examined developmental trajectories of antisocial behavior in females, notably to help determine whether or not an…

The present study examined the association between theory of mind and indirect versus physical aggression, as well as the potential moderating role of prosocial behavior in this context. Participants were 399 twins and singletons drawn from two longitudinal studies in Canada. At five years of age, children completed a theory of mind task and a…