This report presents data on 9-month-old twin pairs (n[MZ]=172; n[DZ]=333) from the Early Childhood Longitudinal Study, demonstrating that the role of genetic variation among infants is trivial and the shared and nonshared environment is substantial in accounting for the observed quality of infant-caregiver relationships. In contrast, maternal…

Estimates the extent to which heredity influences perceptions of childhood family environment in a sample of 58 monozygotic and 46 dizygotic pairs of adult twins who were reared apart. The data confirm the importance of genetic factors in some, but not all, measures of family environment. Environmental influences were more important than genetic…

The mother, father, and adolescent siblings from 675 families were observed interacting in problem-solving sessions. Siblings were monozygotic twins, dyzygotic twins, or full siblings in nondivorced families and full, half, and unrelated siblings in stepfamilies. Results suggested a greater genetic component to adolescent behavior than to parent…

Parents of Swedish twin pairs ages 7 to 9 years and of British twin pairs ages 8 to 16 years completed the Child Behavior Checklist. Found that genetic factors influenced aggressive antisocial behavior to a greater extent than nonaggressive antisocial behavior, which was also significantly influenced by the shared environment. There was a…

Examined the origins of high general cognitive ability (g) in twins who were participating in the MacArthur Longitudinal Twin Study. Formed high g groups from the 19th percentile and above at each age. Results suggested increasing genetic influence and increasing genetic stability from 14 to 36 months and substantial genetic influences with…

Investigated the degree to which individual differences in child-parent attachment were mediated by genetic, shared environmental, and nonshared environmental influences. Found an overall concordance rate of 67 percent at the secure/insecure level. Twin similarity on the continuous measure of attachment security was consistent with a modest role…

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…

The genetic and environmental etiologies of sex-typed behavior were examined during the preschool years in a sample of 3,990 three- to four-year-old twin and nontwin sibling pairs. Results showed moderate genetic and significant shared environmental influence for boys and substantial genetic and moderate shared environmental influence for girls.…

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…

Used data from sibling pairs from the National Longitudinal Study of Adolescent Health to examine how parental education moderated the genetic and environmental contributions to variation in verbal IQ. Found that the variance estimate for heritability was greater than that for shared environment for the whole sample. Both estimates were moderated…

Used behavioral genetic methods and environmental assessment techniques to assess maladaptive behavior in 6- to 11-year-old twin pairs. Found that genetic variation accounts for majority of variance in parent-reported child maladaptive behavior; in contrast, observational coding and global impressions of parent-twin interactive behavior suggest…

The language development of monozygotic twins, same-sex dizygotic twins, siblings of monozygotic twins, and siblings of dizygotic twins, ages 3-17, was studied to estimate how much of the individual variation in children's language skills results from genetic factors and how much from environmental experience. (BRT)

This behavioral genetic study examined perceived competence and self-worth in same-sex twins, siblings, and stepsiblings 10 to 18 years old, and again 3 years later. Findings at second assessment showed six of seven subscales heritable. Genetic contributions to stability were found for perceived scholastic competence, athletic competence, physical…

Some children exposed to socioeconomic (SES) deprivation are resilient and function better than expected, given the level of deprivation they have experienced. The present study tested genetic and environmental contributions to young children's resilience and vulnerability to SES deprivation. Children's resilience was assessed by the difference…

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…