This study bears on Arthur R. Jensen's latest statement on the heritability of intelligence. Allowing for gene-environment correlation, Jensen (1975) reports that under a wide range of assumptions, the twin data show that one-half to three-fourths of IQ variance is accounted for by genetic factors. This conclusion falls when an arbitrary…

Extensive data on twins, nontwin siblings, siblings separated by adoption, and parent-child similarity indicate that the heritability of intelligence is closer to .50 than to .70. Differences could be due to environmental or genetic changes in the population, or to methodology. (Author/CP)

Yearly cognitive tests were administered to adoptive and nonadoptive siblings between one and seven years of age and identical and nonidentical twins between one and three years. Results indicated that genetic influences are a source of continuity and change in mental development, whereas shared and nonshared environmental effects contribute to…

Used the Sibling Inventory of Differential Experience with 396 adolescent and young adult children to determine the extent to which genetic differences between siblings or sibling differences in family constellation variables were responsible for differential experiences. (HOD)

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 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)

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.…

A reply to Plomin's critique and some criticisms of Munsinger's review of adopted child literature are presented. Selective bias in adoptee samples, implicit assumptions in models that lead to heritability estimates, and problems produced by lack of an accepted model of environmental transmission are also discussed. (Author/RD)

A review of the twin literature and analyses of two large twin samples found identical twin correlations higher than fraternal twin correlations by about .20 for a variety of traits of ability, personality and interests. This was interpreted as indicating that about half of the variation among people in a broad spectrum of psychological traits is…

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…

Swedish longitudinal studies of twins support Scarr-Salapatek's explanation of nature-nurture influences on intelligence. This model predicts more genetic variance in test results for advantaged than disadvantaged groups. Jensen's work, however, suggests equal amounts of variance among different social classes. (Author/CP)

Preliminary results from data on 146 Australian, 284 American, and 70 Norwegian preschool twins indicate reliable genetic influences on phonological awareness and memory and learning. Vocabulary, grammar, and morphology showed significant shared environment and negligible genetic effects. A print knowledge composite showed genetic and shared…

Examined environmental and gene-environment processes linking parenting (affect, control, responsiveness) and preschoolers' behavioral adjustment difficulties (noncompliance, conduct problems). Found that estimates of shared environmental variance and mediation were greatest for observational data, and estimates of child genetic variance and…

Examined the genetic and environmental contributions to the predictive association between parenting and adolescent adjustment in identical and fraternal twins, and full, half, and genetically unrelated siblings in nondivorced and stepfamilies. Found that cross-lagged associations between parental conflict-negativity and adolescent antisocial…