Both genes and the environment are important for individual differences in expertise, but little is known about gene-environment interactions underlying domain-specific achievement. Here we explored this issue in a large Swedish twin cohort (N = 6,610), using moderator modeling with musical expertise as a model domain. Specifically, we tested…

The genetic effects on individual differences in reading development were examined using genome-wide complex trait analysis (GCTA) in a twin sample. In unrelated individuals (one twin per pair, n = 2,942), the GCTA-based heritability of reading fluency was ~20%-29% at ages 7 and 12. GCTA bivariate results showed that the phenotypic stability of…

Modern behavior-genetic studies of twins in the United States, Australia, Scandinavia, and the United Kingdom show that genes account for most of the variance in children's reading ability by the end of the 1st year of formal reading instruction. Strong genetic influence continues across the grades, though the relevant genes vary for reading words…

The aim of this longitudinal case study was to describe bimodal and bilingual acquisition in a hearing child, Hugo, especially the role his Deaf family played in his linguistic education. Video observations of the family interactions were conducted from the time Hugo was 10 months of age until he was 40 months old. The family language was Swedish…

This case study longitudinally analyzes and describes the changes of attentional expressions in interchanges between a pair of fraternal twins, 1 deaf and 1 hearing, from the age of 10-40 months, and their Deaf family members. The video-observed attentional expressions of initiating and reestablishing interchange were grouped in 5 functional…

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,…

A research study of identical twins, by Thomas J. Bouchard Jr., discloses that genetics exert a stronger influence over personality than we thought. Parents and teachers are advised to be active and alert observers of children's interests and talents to provide appropriate tools and resources to develop these propensities. (MLF)

This observational study examined the development and use of communication in a pair of deaf and hearing monozygotic twins from 13 to 36 months of age. Both children were enrolled in a total communication preschool program. In contrast to the hearing twin, the deaf twin used imitative (rather than responsive) signs and gestures. (Author/DB)

Two types of behaviours shown in children--those reflecting social impairment and nonsocial obsessive repetitive behaviours--are central to defining and diagnosing autism spectrum disorders (ASDs). Parent and teacher data on social and nonsocial behaviours were obtained from a community sample of greater than 3000 7-year-old twin pairs. Social and…

Background: Childhood psychopathology is associated with both high and low levels of prosocial behaviour. It has been proposed that the development of prosocial behaviour shows emerging and consolidating individual differences as children grow older. The influences on these individual differences have not previously been examined in children and…

This book analyzes the MacArthur Longitudinal Twin Study, a collaborative study by leading developmental scientists and behavioral geneticists on the transition from infancy to early childhood. Part 1 of the book describes the twin method and procedures used and introduces the analytic strategies. Parts 2 through 4 present results related to…