This study examined whether the differential maternal treatment of twins affected the twins' on-task behaviors in a teaching interaction. A total of 175 mothers and their same-sex 14-month-old twins were videotaped in their homes in triads. This was repeated for 170 of the families when the children were 24 months, and for 146 of the families when…

Examines the case of two five-year-old twin boys with delayed language development, yet judged to be articulate and successful students in kindergarten. Suggests that the delay appeared because most of their interaction had been with each other. However, through their family they became acquainted with the discourse activities that are valued at…

This study of 640 twins with reading disability and 436 controls (mean age 12) examined external validity of the distinction between specific reading retardation and reading backwardness, in 3 domains: genetic etiology, sex ratio and clinical correlates, and neuropsychological profiles. There was no evidence of differential genetic etiology of the…

Used between-family analyses of data from adolescent twin girls to offer new evidence that early menarche is associated with earlier initiation and greater frequency of smoking and drinking. Found that association of pubertal timing with substance use could not be explained by between-family confounds, and pubertal timing influence on drinking…

Background: Longitudinal pediatric neuroimaging studies have demonstrated increasing volumes of white matter and regionally-specific inverted U shaped developmental trajectories of gray matter volumes during childhood and adolescence. Studies of monozygotic and dyzygotic twins during this developmental period allow exploration of genetic and…

Background: Differences in personality profiles were examined between children who differed in their co-morbidity of externalizing disorders: attention-deficit/hyperactivity disorder (ADHD) and conduct disorder (CD). Methods: 11- and 17-year-old male and female twins from a community sample were categorized as ADHD only, CD only, co-morbid…

We investigated infant precursors of low language scores in early childhood. The sample included 373 probands in 130 monozygotic (MZ) and 109 same-sex dizygotic (DZ) twin pairs in which at least one member of the pair scored in the lowest 15th percentile of a control sample on a general language factor derived from tester-administered tests at…

This article presents an overview of some methods and results from our continuing studies of genetic and environmental influences on dyslexia, and on individual differences across the normal range that have been conducted over the past 25 years in the Colorado Learning Disabilities Research Center (CLDRC) and in related projects. CLDRC…

The multiple-birth family must struggle to cope with extraordinary issues with little or no information or support, and with little understanding from the community at large. This paper describes such issues and their impact on the lives of families of twins, triplets, quadruplets, and quintuplets from conception through adolescence. An…

The contribution of heredity to scores on a digit span intelligence test, Jensen's Memory for Numbers, was estimated with a standard heritability formula. The test measures level I mental ability--the capacity to store and recall, but not ability to elaborate or manipulate stimuli. Subjects were 35 monozygotic (MZ) twins and 35 same-sex dizygotic…

This book is organized in nine parts, as follows. Part I, "Preface," includes an account of how the author went from the rather esoteric research on theoretical problems in serial rote learning to research on the inheritance of mental abilities and its implications for education. Part II, "How Much Can We Boost IQ and Scholastic Achievement?," is…

This book reports on a study of 850 pairs of twins who were tested to determine the influence of heredity and environment on individual differences in personality, academic ability, and interests. It presents the background, research design, and procedure of the study, tabulations of the test results, and extensive analyses of the findings.…

Reports on the findings of several studies into the genetic similarities of twins. Focuses on the relationships between personality and behavioral genetics and argues that genetic similarity seems to be a better predictor than environmental factors. Discusses psychopathology, cognitive abilities, and personality. (TW)

A sample of twin boys and their mothers was followed up from age 2 to age 9. Mothers' responses to interview questions were compared across these two ages in order to assess mothers' perceptions of continuity or change in given behaviors. Results indicated substantial continuity in mothers' reports of the presence or absence of given behaviors.…

Assessments of the home environments of 116 families whose twins were participants in a longitudinal study of early mental development were conducted. Predictions of offspring intelligence scores increased from ages six months to six years old. Although home/family variables were related to mental development, so were parental education and SES.…