Two studies of twin, sibling, and cousin pairs among children attempted to extend a model, called DF analysis, which separates hereditary and shared environmental influences. First study supported the validity of DF analysis applied to kinship height and weight data. The second study showed that spanking, reading, and quality of home environment…

This commentary details a number of problems with the study design and data analysis reported by Finkel et al. The commentary also provides suggestions for more fruitful approaches for analyzing data from such studies in the future. (Author/BC)

Investigated the degree to which individual differences in child-parent attachment were mediated by genetic, shared environmental, and nonshared environmental influences. Found an overall concordance rate of 67 percent at the secure/insecure level. Twin similarity on the continuous measure of attachment security was consistent with a modest role…

Research on child effects has demonstrated that children's difficult and coercive behavior provokes harsh discipline from adults. Using a genetically sensitive design, the authors tested the limits of child effects on adult behavior that ranged from the normative (corporal punishment) to the nonnormative (physical maltreatment). The sample was a…

To study sources of individual differences in pubertal development, the authors fit a sex-limitation common factor model to data reported, at ages 11 and 14 years, by 1,891 twin pairs on items that comprise the Pubertal Development Scale (PDS; A. C. Petersen, L. Crockett, M. Richards, & A. Boxer, 1988). The model divides variation into a general…

This study of 4-year-old twins investigated the genetic and environmental origins of comorbidity between language impairment and nonverbal ability by testing the extent to which language impairment in one twin predicted nonverbal ability in the co-twin. Impairment of language ability was defined as scores below the 15th percentile on a general…

The genetic and environmental etiologies of sex-typed behavior were examined during the preschool years in a sample of 3,990 three- to four-year-old twin and nontwin sibling pairs. Results showed moderate genetic and significant shared environmental influence for boys and substantial genetic and moderate shared environmental influence for girls.…

Although it is well established that school characteristics (SCH) and socio-economic status (SES) are associated with academic achievement (ACH), these correlations are not necessarily causal. Because academic achievement shows substantial genetic influence, it is useful to embed such investigations in genetically sensitive designs in order to…

Previous studies have suggested that among affected sib pairs with autism there is an increase in the frequency of twins over what would be expected in comparison to the prevalence of twins in the general population. In this study we sought to determine whether "sub-threshold" autistic traits were more pronounced in twins than in non-twins. The…

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 use a genetically sensitive design to examine the relationship between language and nonverbal ability at 4 and a half and reading skills at 7 years of age in a sample of more than 1,000 children participating in the Twins Early Development Study. We find that nonphonological as well as phonological measures of early language make significant…

Using a longitudinal, large-scale sample of British twins, we addressed the prediction of both cognitive abilities and behavioral adjustment from eight domains of environmental risk: minority status, socio-economic status, maternal medical factors, twin medical factors, maternal depression, chaos within the home environment, and parental feelings…

Using multiple births as an exogenous shift in family size, I investigate the impact of the number of children on child investment and child well-being. Using data from the 1980 US Census Five-Percent Public Use Micro Sample, 2SLS results demonstrate that parents facing a change in family size reallocate resources in a way consistent with Becker's…

Dialogues of sets of socially similar twins are studied. The opinion that twins have slower syntactic development than non-twins is seriously questioned. Dialogues with twins saying the same utterance together, correcting each other, quarreling, playing verbal games, etc. are analyzed in their deep structure. (SCC)

In this case study, the language and cognitive development of a 4-year 5-month old profoundly deaf girl and her normally hearing identical twin sister were investigated by videotaping the twins in their home interacting with each other, the investigator, and family members. Materials used with the children were designed to elicit spontaneous,…