Examines genetic influences on language by assessing 158 preschool twins on vocabulary comprehension, semantic knowledge, morphology, syntax, and articulation. Vocabulary comprehension was significantly influenced by heredity, whereas performance skills were influenced by between-family environmental factors. (Author/AS)

An example of controlling" maternal behavior with 3 1/2-month-old twins is studied by a method of frame-by-frame film analysis. Characteristic infant behaviors regulating social contact with the mother are identified and followed through 15 months. (Author)

Standardized mathematics test results of a twin sample during grades 3 and 6 were interpreted according to an interactional heredity x environment model. Results indicated that similar school instruction made monozygotic twins more alike but dizygotic twins less alike in mathematics knowledge. Social background effects were also studied. (SJL)

A computer scan of ACT Assessment records identified 3,427 sets of twins. The Hardy-Weinberg rule was used to estimate the proportion of monozygotic twins in the sample. Matrices of genetic and environmental influences were produced. The heaviest loadings were clearly in the genetic matrix. (SJL)

Gazing behavior of 10 twin infants (five male and five female) and their mothers were recorded weekly during the babies' fourth month of life. Videotape equipment was used in the home; data were gathered as naturalistically as possible. (Author/MS)

Critically examines the portions of Arthur Jensen's books that concern Barbara Burks' 1928 study of adoptive families. Findings are that Burks' sample was highly selective, that her environmental measures were limited, and that Jensen has misrepresented the content and implications of her study. It is also shown that Jensen's estimates of…

Uses data on twins (N=355) to obtain estimates of the degree of shared familial influence on cognitive achievement and academic performance. Results indicate that there is considerable shared influence on cognitive achievement but much less for academic performance, suggesting more between-family variation in cognitive achievement than in academic…

Examined data from 408 pairs of identical, same-sex fraternal twins at 14, 20, and 24 months to assess cognitive development and to identify genetic and environmental influences on phenotypic similarity. Found various patterns of development for separate constructs, for females versus males on each construct, and for individuals across constructs.…

Studies two nonidentical twin boys with severe, specific developmental language disorders with respect to their linguistic, neurolinguistic and pragmatic development. Finds that, in spite of poor linguistic awareness, the boys acquired normal reading/spelling skills; however, the boys differed considerably in some aspects of reading and spelling…

This observational study examined the development and use of communication in a pair of deaf and hearing monozygotic twins from 13 to 36 months of age. Both children were enrolled in a total communication preschool program. In contrast to the hearing twin, the deaf twin used imitative (rather than responsive) signs and gestures. (Author/DB)

A simultaneous presentation procedure to select reinforcers was implemented with two four-year-old twin boys who were developmentally delayed, noncompliant, and mute. Use of the procedure quickly and efficiently identified preferred reinforcers which were then used in an instructional task. (DB)

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)

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…