Written in response to an article (Horn, 1983) that appeared in special Developmental Behavioral Genetics section of CHILD DEVELOPMENT (Volume 54), this commentary (1) notes some issues concerning Horn's analysis and interpretation of data and (2) highlights the potential for interpretational bias in behavior genetics research. (Author/BE)

In this rebuttal to Walker and Emory's commentary (also in this issue), Horn argues that the issue of the influence of environment on the average IQ of adopted children was well discussed in his article (Volume 54 of CHILD DEVELOPMENT). (BE)

The home environment of nonadoptive and adoptive sibling pairs was assessed using the Home Observation for Measurement of the Environment when each sibling was one and two years of age. Correlations between home environment scores for nonadoptive siblings were greater than those for adoptive siblings. (BC)

Correlations on subscales of Wechsler intelligence quotient tests and the Revised Beta Examination were obtained for biologically related and unrelated individuals in 181 adoptive families in the Texas Adoption Project. Generally higher correlations for biologically related individuals support the importance of genetic influence in intellectual…

Used the sibling adoption design to investigate teacher and tester ratings of child temperament. Ratings on the Colorado Childhood Temperament Inventory were obtained from a teacher and a tester for pairs of adopted and nonadoptive seven-year-old siblings. Significant genetic influence emerged for tester ratings of Activity and Sociability and for…

Studied continuity and change in general cognitive ability from infancy to adolescence in adoptees (107 children), biological siblings (87 pairs), and twins (224 monozygotic and 189 dyzygotic pairs). Findings generally support previous findings about genetic and environmental factors, with the exception that in the transition to adolescence,…

Pairs of genetically unrelated children reared as same-age siblings offer a design for investigating genetic and environmental influences on behavior. Results with 21 pairs support an explanatory model of intelligence that includes genetic factors. Shared environment appeared to have a very small effect on intellectual development. (SLD)

Conducted a trivariate genetic analysis of the Home Observation for Measurement of the Environment (HOME), Mental Development Index (MDI), and Task Orientation (TO). Found that for 101 nonadoptive and 92 adoptive sibling pairs at 12 and 24 months of age, TO explained the remaining genetic variance on the HOME not explained by the MDI. (MDM)

A parent-offspring adoption path model, with a measured index of the home environment, was developed to assess extent to which genetic and environmental influences of the parents affect relationships between the environmental index and children's behavior. Intelligence Quotient (IQ) data from the Colorado Adoption Project were used. The…

Genetic effects on specific cognitive abilities as distinct from those on general cognitive ability were studied in 302 pairs of twins (some reared together, some apart) from the Swedish Adoption/Twin Study of Aging. Overall, results showed significant genetic influence on specific abilities independent of influence on general ability. (SLD)

The effects of family background on adolescents' IQ, aptitude, and school achievement test scores challenge some of the usual beliefs about the fairness of achievement rather than IQ tests, and the role of genetic differences among individuals and social class groups in academic achievements. Subjects included 115 adoptive families with adolescent…

The present study is a behavioral genetic analysis of specific cognitive abilities in early childhood. Parent-offspring data for adopted children and nonadopted children in the Colorado Adoption Project were used. Significant correlations were found between biological mothers' IQ and the IQ of offspring, but not for specific cognitive abilities.…

The Infant Behavior Record (IBR) assessed the temperament of 95 nonadoptive and 80 adoptive sibling pairs at 1 and 2 years of age. Data from this and an earlier similar study of identical and fraternal twins yielded evidence for genetic influence for IBR factors of extraversion, activity, and task orientation. (BC)

Explored aggression and delinquency in unrelated adoptive sibling pairs and biologically-related sibling pairs in the Colorado Adoption Project at 7, 9, 10, 11, and 12 years. Found that boys and adopted children were higher in externalizing behavior problems than girls and biologically related pairs. Sex differences in delinquency were more…

Focuses on possibility that correlations between measures of environment and child devleopment can be mediated genetically as well as environmentally. Proposing an elementary model to test this hypothesis, data from classical adoption studies and new data from the Colorado Adoption Project are used to illustrate the model and provide quantitative…