Anxiety and conduct problems covary, yet studies have not explored the genetic and environmental origins of this association. We analyzed parent-reported anxiety and conduct problems in 6,783 pairs of twins at 2-, 3-, and 4-years of age. As anxiety and conduct problems were fairly stable across the three ages (average 1-year correlation was .53),…

The genetic and environmental etiologies of 3 aspects of low mathematical performance (math disability) and the full range of variability (math ability) were compared for boys and girls in a sample of 5,348 children age 10 years (members of 2,674 pairs of same-sex and opposite-sex twins) from the United Kingdom (UK). The measures, which we…

Twin children were videotaped hitting an inflated clown figure. Three behaviors (number of hits, intensity of hits, and number of quadrants hit) showed adequate response characteristics, rater reliability, and test-retest reliability. Twin analyses of the three behavioral ratings yielded no evidence of hereditary influence. (Author)

Despite the importance of learning abilities and disabilities in education and child development, little is known about their genetic and environmental origins in the early school years. We report results for English (which includes reading, writing, and speaking), mathematics, and science as well as general cognitive ability in a large and…

Obtained objective measures of activity, fidgeting, vigilance, selective attention, and aggression for a sample of 87 twin pairs in late childhood. Little evidence for genetic influence on behavior was found. Between-family environmental sources of variance were far more important than within-family factors. (Author/RH)

Multivariate genetic analysis was used to examine the genetic and environmental aetiology of the interrelationships of diverse linguistic skills. This study used data from a large sample of 4 1/2-year-old twins who were tested on measures assessing articulation, phonology, grammar, vocabulary, and verbal memory. Phenotypic analysis suggested two…

Studied continuity and change in general cognitive ability from infancy to adolescence in adoptees (107 children), biological siblings (87 pairs), and twins (224 monozygotic and 189 dyzygotic pairs). Findings generally support previous findings about genetic and environmental factors, with the exception that in the transition to adolescence,…

Examined infant verbal and nonverbal cognitive development for 1,937 pairs of same-sex 2-year-old twins. Found that verbal and nonverbal development correlated .42. Genetic factors were responsible for less than half of this phenotypic correlation. The genetic correlation between verbal and nonverbal abilities was only .30, suggesting that genetic…

Provides an overview of a longitudinal, prospective, multivariate adoption study of behavioral development and discusses the results of analyses of cognitive measures and environmental assessments as examples of the types of information that can emerge from a design of this sort. (Author/RH)

Conducted a trivariate genetic analysis of the Home Observation for Measurement of the Environment (HOME), Mental Development Index (MDI), and Task Orientation (TO). Found that for 101 nonadoptive and 92 adoptive sibling pairs at 12 and 24 months of age, TO explained the remaining genetic variance on the HOME not explained by the MDI. (MDM)

Examined genetic and environmental contribution to self-reported peer-group characteristics among adoptive and nonadoptive adolescent sibling pairs. Found that although peer preference is influenced, in large part, by nonshared environment factors, genetic influence is present. Substantial genetic influence emerged for college orientation, and…

The present study is a behavioral genetic analysis of specific cognitive abilities in early childhood. Parent-offspring data for adopted children and nonadopted children in the Colorado Adoption Project were used. Significant correlations were found between biological mothers' IQ and the IQ of offspring, but not for specific cognitive abilities.…

Explored aggression and delinquency in unrelated adoptive sibling pairs and biologically-related sibling pairs in the Colorado Adoption Project at 7, 9, 10, 11, and 12 years. Found that boys and adopted children were higher in externalizing behavior problems than girls and biologically related pairs. Sex differences in delinquency were more…

Focuses on possibility that correlations between measures of environment and child devleopment can be mediated genetically as well as environmentally. Proposing an elementary model to test this hypothesis, data from classical adoption studies and new data from the Colorado Adoption Project are used to illustrate the model and provide quantitative…

Language development was studied in 310 pairs of 4-year-old twins. Rotated factor analyses indicated presence of a general language factor (L) and a general nonverbal factor (NV). Moderate genetic influence was found for L and NV abilities. Bivariate genetic analysis estimated a genetic correlation of .63 between L and NV abilities. Results…