Randomized control trials are considered the pinnacle for causal inference. In many cases, however, randomization of participants in social work research studies is not feasible or ethical. This paper introduces the co-twin control design study as an alternative quasi-experimental design to provide evidence of causal mechanisms when randomization…

Valid and reliable teacher ratings serve as the foundation for screening and assessment of youth with behavioral disorders and twin studies offer an opportunity to study those ratings. We conducted a meta-analysis of 15 empirical investigations of aggressive and rule-breaking behavior using teacher ratings in the context of a twin research design.…

Current evidence suggests the phenotype of autism spectrum disorder to be driven by a complex interaction of genetic and environmental factors impacting onto brain maturation, synaptic function, and cortical networks. However, findings are heterogeneous, and the exact neurobiological pathways of autism spectrum disorder still remain poorly…

Delayed reward discounting is a behavioral economic index of impulsivity, referring to how much an individual devalues a reward based on its delay in time. As a behavioral process that varies considerably across individuals, delay discounting has been studied extensively as a model for self-control, both in the general population and in clinical…

Reviews family, linkage, and twin studies of reading disability. Reports on application of behavioral genetic methods to reading performance data from 96 identical twin pairs and 72 fraternal twin pairs in which at least one twin was reading disabled. Found approximately one-half of the reading deficit observed in the probands may have been…

Research shows that many schools implement strict policies for classroom placement of twins, yet the effects of such policies on twins' development and educational attainment are currently unknown. Recommendations for school personnel and future directions for this formative area are discussed. (Contains 39 references.) (GCP)

This article reviews research regarding the effect of heredity on athletic performance. Research on twins indicates that genetic makeup may have a strong role in aerobic capacity, adaptability to training, composition of muscle tissue, and personality traits relating to competitiveness and leadership. (CB)

Studies of families, twins, and adoptees support a genetic predisposition to alcoholism. Alcohol metabolism may affect the regulation of alcohol intake, because interference with production or elimination of the alcohol metabolite acetaldehyde has behavioral effects. Ongoing research is examining individual and tribal differences in alcohol…

Provides a comprehensive contemporary summary of the world literature on IQ correlations between relatives. A profile of average correlations consistent with a polygenic mode of inheritence is revealed from a summary of 111 studies, although a marked degree of heterogeneity of the correlations within familial groupings is also found. (CS)

Findings from a study in which twins were given tests of onward repetition and auditory processing are discussed. Children with specific language impairments were impaired on both measures, but deficits had different origins. Auditory processing problems showed no evidence of genetic influence, whereas the nonword repetition deficit was highly…

Reviews biological bases of twinning and descriptions of 10 research designs. Summarizes findings from a selected sampling of twin studies of learning disabilities, personality and temperament, attitudes, psychopathology, and social behavior. Discusses findings with special reference to the activities of mental health practitioners and counselors.…

The author, herself a mother of twins, reviews research on exceptional twins. She considers reasons for fascination with twins and comments upon important advances in technology. Current research in Indianapolis to measure cognitive, perceptual, personality, and chromosome patterns of twins is described. Differences in the makeup of identical and…

Virtual twins are unrelated siblings of the same age who are reared together from early infancy (UST-SA). Study uses a sample of 90 UST-SA pairs to comparatively assess the similarity of IQ subtest profile correlations for UST-SAs and twin pairs. Findings support explanatory models of intelligence that include genetic factors, demonstrating that…

We conducted behavior?genetic analyses of kindergarten reading, spelling, phonological awareness, rapid naming, and spoken sentence processing in 172 pairs of monozygotic and 153 pairs of same-sex dizygotic twin kindergarten children sampled in the United States and Australia. We also modeled progress from preschool to kindergarten in…

"Twins have often served science but science has rarely served twins" (Novotny, 1988). Twinship presents specific challenges unique to twins in the realms of physical, emotional, social, interpersonal, and academic trials; twins many times suffer in self-esteem, separation-individuation, and object relations. This paper reviews literature which…