Variability in achievement across learners is a hallmark of second language (L2) learning, especially in academic-based learning. The Twins Early Development Study (TEDS), based on a large, population-representative sample in the United Kingdom, provides the first opportunity to examine individual differences in second language achievement in a…

During childhood and adolescence, increases in heritability and decreases in shared environmental influences have typically been found for cognitive abilities. A sample of more than 2,500 pairs of twins from the Twins Early Development Study was used to investigate whether a similar pattern would be found for science performance from 9 to 12…

Background: High levels of clinical comorbidity have been reported between autistic spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD). This study takes an individual differences approach to determine the degree of phenotypic and aetiological overlap between autistic traits and ADHD behaviours in the general population.…

Purpose: Language acquisition is predictive of successful reading development, but the nature of this link is poorly understood. Method: A sample of 7,179 twin pairs was assessed on parent-report measures of syntax and vocabulary at ages 2, 3, and 4 years and on teacher assessments of reading achievement (RA) at ages 7, 9, and 10 years. These…

Background: Are there sex differences in the etiology of high performance in science in childhood that could contribute to the under-representation of women in scientific careers? In this study the relative contributions of genetic and environmental influences on high performance in science in both boys and girls were assessed using standard twin…

A behavioral genetic analysis of general writing ability was conducted using teacher assessments based on UK National Curriculum criteria for a sample of 3296 same-sex pairs of 7-year-old twins. Writing was highly heritable within the normal range (0.66) and at the low extreme (0.70). Environmental influences were almost all non-shared, with…

Little is known about the underlying causes and developmental patterns of stability and change in early reading abilities. In a longitudinal study of twins (n=4,291 pairs), individual differences in reading achievement assessed by teachers using U.K. National Curriculum (NC) criteria showed substantial heritabilities at ages 7, 9, and 10 years…

Background: Individuals with early warning signs of life-long psychopathy, callous-unemotional traits (CU) and high levels of antisocial behaviour (AB) can be identified in childhood. We report here the first twin study of high levels of psychopathic tendencies in young children. Methods: At the end of the first school year, teachers provided…

Non-shared environmental influence (NSE) has been found to account for around 50 percent of anxiety variance, but specific NSE factors have not been identified. Discordant monozygotic (MZ) twins can be used to generate relevant hypotheses because MZ discordance can be caused by NSE, but not by genes or shared environment. Of 1590 MZ pairs teacher…

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…

This longitudinal monozygotic (MZ) twin differences study explored associations between birthweight and early family environment and teacher-rated behaviour problems and academic achievement at age 7. MZ differences in anxiety, hyperactivity, conduct problems, peer problems and academic achievement correlated significantly with MZ differences in…