Studies have identified concurrent, longitudinal, and bidirectional associations between language difficulties and internalizing problems. This is commonly explained by social exclusion or withdrawal from peers, but underlying mechanisms are not well understood. This study uses sibling data to investigate if the comorbidity between language…

Early diagnosis of autism spectrum disorder is challenging due to its phenotypic and etiological heterogeneity, but critical for implementation of early interventions. We examined the age of autism spectrum disorder diagnosis in a sample of 554 children and adolescents enrolled in the ELENA cohort study in France with regard to the influences of…

Background: Previous research has largely focused on evaluating the impact of teaching practical parenting skills to parents with intellectual disabilities. Teaching them about the importance and nature of early attachment behaviors has not yet been explored. This study investigates whether knowledge of early attachment behavior of young adults…

Girls who receive higher quality fathering engage in less risky sexual behavior (RSB) than their peers. Previous research identifies higher levels of parental monitoring/knowledge and reduced affiliation with deviant peers as potential mediators of this observed fathering effect. Although paternal investment theory posits a causal effect of…

Youth who experience adverse environments in early life initiate sexual activity at a younger age, on average, than those from more advantaged circumstances. Evolutionary theorists have posited that ecological stress precipitates earlier reproductive and sexual onset, but it is unclear how stressful environments interact with genetic influences on…

Research suggests that sibling--peer connections are important for understanding adolescent problem behaviors. Using a novel behavioral genetic design, the current study investigated peer network overlap in 300 child--child pairs (aged 7-13 years) in 5 dyad types: monozygotic (MZ), dizygotic twins, full siblings (FSs), friend pairs, and virtual…

Endophenotypes or intermediate phenotypes are of great interest in neuropsychiatric genetics because of their potential for facilitating gene discovery. We evaluated response inhibition, latency and variability measures derived from the stop task as endophenotypes of ADHD by testing whether they were related to ADHD traits in the general…

Background: Adolescent involvement in religious organizations has been hypothesized to protect against early age at first drink. However, the correlation between adolescent religiosity and later age at first drink may be confounded by environmental or genetic differences between families. This study tests whether, after controlling for shared…

Research has supported the existence of distinct behavioral patterns, demographic correlates, and etiologic mechanisms for aggressive (AGG) versus nonaggressive but delinquent (DEL) antisocial behavior. Though behavioral genetic studies have the potential to further crystallize these dimensions, inconsistent results have limited their…

The etiology of individual differences in general verbal ability, verbal learning and letter and category fluency were examined in two independent samples of 9- and 18-year-old twin pairs and their siblings. In both age groups, we observed strong familial resemblance for general verbal ability and moderate familial resemblance for verbal learning,…

We studied the age-related differences in inspection time and multiple cognitive domains in a group of monozygotic (MZ) and dizygotic (DZ) twins aged 7 to 17 years. Data from 111 twin pairs and 19 singleton siblings were included. We found clear age-related trends towards more efficient visual information processing in older participants. There…

Behavioral genetic research has concluded that the more important environmental influences result in differences between siblings (referred to as "nonshared"; "e[superscript 2]"), whereas environmental influences that create similarities between siblings (referred to as "shared"; "c[superscript 2]") are indistinguishable from zero. However, there…

The relation between intelligence and birth order was shown in a recent publication [Bjerkedal, T., Kristensen, P., Skjeret, G. A. & Brevik, J. I. (2007). Intelligence test scores and birth order among young Norwegian men (conscripts) analyzed within and between families. "Intelligence," 35, 503-514] to be negative. Subjects in this…

The behaviors and interactions of preschool-aged siblings in object-oriented and body-oriented conditions were observed to discover if the child's siblings significantly influenced motor skill development. This study focused on categories of sibling behaviors and interactions. (Author/DF)

IQ scores from five kinship categories of 7- to 12-year-olds were analyzed into genetic and environmental components. The common environmental effects were larger for older children than younger children. Overall, the Genetic and Common Environment Sources each accounted for approximately 40% of the IQ variability in the data. (Author/LMO)