The aim of this study was to disentangle pervasive from situational antisocial behaviors using multiple informants, and to investigate their genetic and environmental etiologies in preadolescence and across time. Antisocial behaviors were assessed in 2,232 twins from the Environmental Risk (E-Risk) Longitudinal Twin Study at ages 5 and 12.…

Recent evidence has suggested that sleep may facilitate language learning. This study examined variation in language ability in 29 toddlers with Down syndrome (DS) in relation to levels of sleep disruption. Toddlers with DS and poor sleep (66%, n = 19) showed greater deficits on parent-reported and objective measures of language, including…

The present study investigated the genetic and environmental covariance between psychopathic personality traits with reactive and proactive aggression in 9- to 10-year-old twins (N = 1,219). Psychopathic personality traits were assessed with the Child Psychopathy Scale (D. R. Lynam, 1997), while aggressive behaviors were assessed using the…

Aggressive behavior in middle childhood is at least partly explained by genetic factors. Nevertheless, estimations of simple effects ignore possible gene-environment interactions (G x E) or gene-environment correlations (rGE) in the etiology of aggression. The present study aimed to simultaneously test for G x E and rGE processes between…

Evidence suggests that sensitivity to coherent motion (CM) is related to reading, but its role in the etiology of developmental dyslexia remains unclear. In this longitudinal study, CM sensitivity was measured in 31 children at family risk for dyslexia and 31 low-risk controls. Children, diagnosed with dyslexia in third grade (mean age = 8 years 3…

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…

Although genetic influences on individual differences in activity level (AL) are well documented, few studies have considered the etiology of AL from a contextual perspective. In the present study, cross-situational and context-specific genetic effects on individual differences in AL at age 2 were examined. The AL of 312 twin pairs (144…

Using a genetic design of 840 60-month-old twins, this study investigated the genetic and environmental contributions to (a) individual differences in four components of cognitive school readiness, (b) the general ability underlying these four components, and (c) the predictive association between school readiness and school achievement. Results…

There is a robust association between prenatal smoking and disruptive behavior disorders, but little is known about the emergence of such behaviors in early development. The association of prenatal smoking and hypothesized behavioral precursors to disruptive behavior in toddlers (N=93) was tested. Exposed toddlers demonstrated atypical behavioral…

Three studies investigated children's belief in causal determinism. If children are determinists, they should infer unobserved causes whenever observed causes appear to act stochastically. In Experiment 1, 4-year-olds saw a stochastic generative cause and inferred the existence of an unobserved inhibitory cause. Children traded off inferences…

The genetic and environmental etiologies of diverse aspects of language ability and disability, including articulation, phonology, grammar, vocabulary, and verbal memory, were investigated in a U.K. sample of 787 pairs of 4.5-year-old same-sex and opposite-sex twins. Moderate genetic influence was found for all aspects of language in the normal…

Examines and rejects common criticisms of the causality concept; shows causality is a relation implied in the grammar of a language about objects. Discusses objective criteria for concepts of causal relations and explains how the concept of causality may be modified to have causes determine probabilities of outcomes. (Author/RH)

Two experiments demonstrated that by the age of four years, children can use the difference between an object's initial and final state to work out what happens to an object when it changes. In contrast, three-year-old children have difficulty in using the difference between initial and final states to make a causal inference. (RH)

Demonstrates ways in which conclusions about models may be affected by violations of the assumption that the observed variables are normally distributed. Addresses the issue of the robustness of findings obtained under such conditions. (Author/RH)

Argues that standard structural equation modeling applied to cross-sectional data almost invariably results in misleading findings concerning relations among variables. Describes the latent longitudinal approach to causal modeling. The approach is one that fits longitudinal models to data, even if only cross-sectional data are available.…