Vocabulary knowledge was tested in a native (Cantonese-Chinese) and foreign (English) language in 150 twins and 150 singletons aged 6-11 years, matched on age, gender, grade level, nonverbal intelligence, parents' education, family income, and number of siblings and household members. The singletons clearly outperformed the twins on the native…

Findings indicated that zygosity was not related to behavioral scores during the neonatal period, and that environment substantially influenced neonatal temperament. Specific perinatal indicators of risk were found to account for some of the intrapair differences in behavioral variables. (RH)

A path model of genetic and family environmental transmission was fitted to published twin correlations and to general cognitive ability data from adoptive and nonadoptive families in which children were tested yearly through the fourth year. Longitudinal genetic correlations from infancy to adulthood were modeled explicitly, as were effects of…

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…

Investigates differences in the language learning environments of six twin pairs and 12 singleton toddlers (all firstborn) with special reference to pragamatic factors that might be expected to differ in dyadic and triadic interactive situations. (HOD)

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)