Explored genetic and environmental etiologies of individual differences in printed word recognition and related skills in identical and fraternal twin 8- to 18-year-olds. Found evidence for moderate genetic influences common between IQ, phoneme awareness, and word-reading skills and for stronger IQ-independent genetic influences that were common…

Analysis of speech samples from four-year-old monozygotic and dizygotic twins revealed that the monozygotic twins were significantly more likely to misproduce the same sound on an articulation test than were dizygotic twins. The dizygotic twins were no more likely to share errors than were children who were both genetically and environmentally…

The communicative abilities of six sets of same-sex, preschool dizygotic twins were examined. In each dyad, one sibling had a strong history of recurrent otitis media (ROM) but the other twin did not. History of ROM was associated with lowered receptive vocabulary, with no consistent effects detected in expressive speech and language tasks.…

Fits spelling data from identical and fraternal twins to a basic multiple regression model. Finds that about 60% of the deficit of probands was due to heritable influences. Finds a nonsignificant sex difference. Suggests collaborative analyses of data from additional twin studies of reading disability to facilitate more rigorous tests. (RS)

Reexamines Ashenfelter and Krueger's estimates of schooling returns (13%), using three additional years of the same twins survey. Finds a 10% return per year of schooling completed. The within-twin regression estimate of schooling's effect in the log wage is smaller than the cross-sectional estimate. (14 references) (MLH)

Summarizes the literature on twins-based estimations of schooling returns. Examines implications of endogenous determination of which twin goes to school longer and of measuring schooling with error. Twin-based estimation may complement other methodologies, but is vulnerable to the same inconsistency that afflicts conventional cross-sectional…

A study involving 494 twins with a reading disability (RD) and 373 typical twins found that individuals with RD were more likely to meet criteria for attention-deficit/hyperactivity disorder (ADHD) and that the association between RD and ADHD was stronger for symptoms of inattention than for hyperactivity symptoms. (Contains extensive references.)…

Data from a large sample of Australian twins indicate that 50 to 65 percent of variance in educational attainments can be attributed to genetic endowments. Only about 25 to 40 percent may be due to environmental factors, depending on adjustments for measurement error and assortative mating. (Contains 51 references.) (MLH)

This case study examines the shifting bilingual preference of three French/English bilingual children over a 3-year period. Clarifies terms used to refer to bilingual preference. The children's fluctuating bilingual preference was accounted for in terms of three contextual domains: home (predominantly French-speaking), school, and community…

Examined genetic and environmental contribution to self-reported peer-group characteristics among adoptive and nonadoptive adolescent sibling pairs. Found that although peer preference is influenced, in large part, by nonshared environment factors, genetic influence is present. Substantial genetic influence emerged for college orientation, and…

Used data from sibling pairs from the National Longitudinal Study of Adolescent Health to examine how parental education moderated the genetic and environmental contributions to variation in verbal IQ. Found that the variance estimate for heritability was greater than that for shared environment for the whole sample. Both estimates were moderated…

Objective: To study the genetic and environmental contributions to stability and change of attention-deficit/hyperactivity disorder (ADHD) symptoms between 8 and 9 and 13 and 14 years of age. Method: The sample included 1,480 twin pairs born in Sweden between May 1985 and December 1986. At wave 1 in 1994, when twins were 8-9 years old, 1,106 (75%)…

Objective: To examine gender differences in attention-deficit/hyperactivity disorder ("ADHD") symptom comorbidity with "oppositional defiant disorder", "conduct disorder", "separation anxiety disorder", "generalized anxiety disorder", speech therapy, and remedial reading in children. Method: From…

Background: A fundamental issue for child psychology concerns the origins of individual differences in early reading development. Method: A measure of word recognition, the Test of Word Reading Efficiency (TOWRE), was administered by telephone to a representative population sample of 3,909 same-sex and opposite-sex pairs of 7-year-old twins.…

This study was a longitudinal examination (21 month follow-up) of language development in a pair of fraternal twins. One twin received a cochlear implant at age 20 months secondary to sensorineural hearing loss. The other twin had normal hearing. Data were obtained every 6 months following her initial cochlear implant stimulation. Both twins…