This study was designed to assess genetic influence on behavioral inhibition and its varying expression in 92 monozygotic and 86 dizygotic twin pairs. Infant behavior and mother-child interaction were observed and videotaped during structured play sessions at age 14, 20, 24, and 36 months. Analysis of the results suggests that most of the overlap…

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)

To demonstrate the value of behavioral genetic analysis for developing social theory, the origins of delinquent behavior were studied in 265 pairs of twins. Results show that causal sequences leading to delinquency are traceable to individual differences in genes. These findings, however, do not make sociological research irrelevant. (KH)

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…

Word recognition data from identical and fraternal twins and siblings (N=172) indicated that the phonological coding deficit of children with reading disabilities was highly heritable. Orthographic coding was not significantly heritable. Poor readers with low IQs were superior to similar reading but average IQ readers in phonological coding.…

This study of 707 sibling pairs, 10- to 18-years-old, examined parent-child and sibling interactions to determine the effects of genetics on family environment. The sample included identical and fraternal twins and full siblings in nondivorced families, as well as full, half, and unrelated siblings in divorced families. Found significant genetic…

Reviews the controversy surrounding the work of Cyril Burt on the genetic contribution to mental ability and argues that the disparagement of Burt's results provides one of the most extraordinary cases of counterfeit charges in academic psychology. Suggesting genetic differences in brain size or intellect is politically incorrect. (SLD)

Describes the interdisciplinary research of Myrtle B. McGraw; examines the controversy about McGraw's concept of critical period; and assesses her impact on current research. McGraw contended that the overlapping phases involved in neuromuscular integration demonstrate that learning and maturation interact during development. (BC)

Parents who were identical twins, fraternal twins, or adopted siblings completed questionnaires assessing attitudes toward parenting and specific parenting practices, the emotional atmosphere of the home, and parental personality. Model-fitting results implicated modest genetic effects on affect-related aspects of parenting, such as parental…

The language of twins allows researchers in language development to examine acquisition in a unique environment. Researchers investigating the nature-nurture controversy, the order of acquisition, and other linguistic features find the twin situation particularly interesting because of the children's shared genetic makeup and environment. A…

Genetic and environmental correlations among 11 Wechsler Intelligence Scale for Children-Revised (WISC-R) subtests were estimated from a sample of 143 twin pairs using the methodology of multivariate behavioral genetics. Correlations due to within-pair environmental influences were generally small, whereas those due to shared environmental…

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…

Objective: To estimate the genetic and environmental contributions to oppositional defiant behavior (ODB) from mother, father, and teacher report using the Conners Revised Short Forms in a large twin sample. Method: ODB data were collected from 1,595 mothers, 1,114 fathers, and 793 teachers of 7-year-old twin pairs from the Netherlands Twin…

Extending the classical twin method, Arthur R. Jensen claims to find unique estimates of the variance and covariance of the genetic and environmental components of IQ. The analyses presented in this paper show that a wide variety of parameter estimates are compatible with his model and data. But the extent of indeterminancy is deemed to be even…