We tested the hypothesis that mother-child warmth and responsiveness would moderate the link between young children's theory of mind skills and self-worth. Participants included 125 same-sex pairs of 3.5 year-old twins and their mothers. A battery of tests was individually administered to measure the children's theory of mind skills and verbal…

A longitudinal investigation of the social and cognitive development of male twins was conducted when twins were 2.5 years of age, and again when they were 8- to 10-years-old. This study was designed to re-examine the heritability of the traits studied at the earlier age and, thus, to address the question of the stability of genetic determination.…

The current study examined whether socioeconomic status (SES) and chaos in the home mediate the shared environmental variance associated with cognitive functioning simultaneously estimating genetic influences in a twin design. Verbal and nonverbal cognitive development were assessed at 3 and 4 years for identical and same-sex fraternal twin pairs…

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…

Standardized clinical assessments from the point of view of children are rare. A standardized narrative assessment measure, developed to assess children's perceptions of their caregiving environments, the Narrative Story-Stem Technique (NSST), was used with two fraternal twins, age 8, with histories of severe maltreatment and multiple foster…

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…

The hypothesis, that the importance of language to mankind lies not so much in the fact that it is the means by which we cooperate and communicate with each other as in the fact that it enables each of us, as individuals and in cooperation, to represent the world to ourselves as we encounter it, is presented. In infancy, the representation is made…

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…