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Grasby, Katrina L.; Coventry, William L.; Byrne, Brian; Olson, Richard K. – Child Development, 2019
Socioeconomic status (SES) has been found to moderate the influence of genes and the environment on cognitive ability, such that genetic influence is greater when SES is higher, and the shared environment is greater when SES is lower, but not in all Western countries. The effects of both family and school SES on the heritability of literacy and…
Descriptors: Socioeconomic Status, Literacy, Numeracy, Foreign Countries
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Peterson, Robin L.; Pennington, Bruce F.; Samuelsson, Stefan; Byrne, Brian; Olson, Richard K. – Journal of Speech, Language, and Hearing Research, 2013
Purpose: The goal of this study was to investigate the etiologic basis for the association between deficits in phonological memory (PM) and vocabulary in school-age children. Method: Children with deficits in PM or vocabulary were identified within the International Longitudinal Twin Study (ILTS; Samuelsson et al., 2005). The ILTS includes 1,045…
Descriptors: Etiology, Phonology, Short Term Memory, Vocabulary
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Olson, Richard K.; Keenan, Janice M.; Byrne, Brian; Samuelsson, Stefan; Coventry, William L.; Corley, Robin; Wadsworth, Sally J.; Willcutt, Erik G.; DeFries, John C.; Pennington, Bruce F.; Hulslander, Jacqueline – Scientific Studies of Reading, 2011
Genetic and environmental relations between vocabulary and reading skills were explored longitudinally from preschool through Grades 2 and 4. At preschool there were strong shared-environment and weak genetic influences on both vocabulary and print knowledge but substantial differences in their source. Separation of etiology for vocabulary and…
Descriptors: Reading Comprehension, Genetics, Word Recognition, Etiology
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Ebejer, Jane L.; Coventry, William L.; Byrne, Brian; Willcutt, Erik G.; Olson, Richard K.; Corley, Robin; Samuelsson, Stefan – Scientific Studies of Reading, 2010
Twin children from Australia, Scandinavia, and the United States were assessed for inattention, hyperactivity-impulsivity, and reading across the first 3 school years. Univariate behavior-genetic analyses indicated substantial heritability for all three variables in all years. Longitudinal analyses showed one genetic source operating across the…
Descriptors: Elementary School Students, Foreign Countries, Attention Deficit Hyperactivity Disorder, Genetic Disorders
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Samuelsson, Stefan; Byrne, Brian; Olson, Richard K.; Hulslander, Jacqueline; Wadsworth, Sally; Corley, Robin; Willcutt, Erik G.; DeFries, John C. – Learning and Individual Differences, 2008
Genetic and environmental influences on early reading and spelling at the end of kindergarten and Grade 1 were compared across three twin samples tested in the United States, Australia, and Scandinavia. Proportions of variance due to genetic influences on kindergarten reading were estimated at 0.84 in Australia, 0.68 in the U.S., and 0.33 in…
Descriptors: Twins, Spelling, Early Reading, Genetics
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Byrne, Brian; Coventry, William L.; Olson, Richard K.; Hulslander, Jacqueline; Wadsworth, Sally; DeFries, John C.; Corley, Robin; Willcutt, Erik G.; Samuelsson, Stefan – Journal of Research in Reading, 2008
As part of a longitudinal twin study of literacy and language, we conducted a behaviour-genetic analysis of orthographic learning, spelling and decoding in Grade 2 children (225 identical and 214 fraternal twin pairs) in the United States and Australia. Each variable showed significant genetic and unique environment influences. Multivariate…
Descriptors: Twins, Spelling, Genetics, Foreign Countries
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Samuelsson, Stefan; Olson, Richard; Wadsworth, Sally; Corley, Robin; DeFries, John C.; Willcutt, Erik; Hulslander, Jacqueline; Byrne, Brian – Reading and Writing: An Interdisciplinary Journal, 2007
Genetic and environmental influences on prereading skills in preschool and on early reading and spelling development at the end of kindergarten were compared among samples of identical and fraternal twins from the U.S. (Colorado), Australia, and Scandinavia. Mean comparisons revealed significantly lower preschool print knowledge in Scandinavia,…
Descriptors: Foreign Countries, Early Reading, Reading Instruction, Kindergarten
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Byrne, Brian; Samuelsson, Stefan; Wadsworth, Sally; Hulslander, Jacqueline; Corley, Robin; DeFries, John C.; Quain, Peter; Willcutt, Erik G.; Olson, Richard K. – Reading and Writing: An Interdisciplinary Journal, 2007
Grade 1 literacy skills of twin children in Australia (New South Wales) and the United States (Colorado) were explored in a genetically sensitive design (N = 319 pairs). Analyses indicated strong genetic influence on word and nonword identification, reading comprehension, and spelling. Rapid naming showed more modest, though reliable, genetic…
Descriptors: Longitudinal Studies, Emergent Literacy, Preschool Children, Kindergarten
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Byrne, Brian; Olson, Richard K.; Samuelsson, Stefan; Wadsworth, Sally; Corley, Robin; DeFries, John C.; Willcutt, Erik – Journal of Research in Reading, 2006
Prereading and early reading skills of preschool twin children in Australia, Scandinavia and the United States were explored in a genetically sensitive design (max. N=627 preschool pairs and 422 kindergarten pairs). Analyses indicated a strong genetic influence on preschool phonological awareness, rapid naming and verbal memory. Print awareness,…
Descriptors: Genetics, Environmental Influences, Emergent Literacy, Twins
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Samuelsson, Stefan; Byrne, Brian; Quain, Peter; Wadsworth, Sally; Corley, Robin; DeFries, John C.; Willcutt, Eric; Olson, Richard – Journal of Educational Psychology, 2005
Individual differences in measures of prereading skills and in questionnaire measures of 4-5-year-old twins' print environments in Australia, Scandinavia, and the United States were explored with a behavioral-genetic design. Modest phenotypic correlations were found between environmental measures and the twins' print knowledge, general verbal…
Descriptors: Foreign Countries, Environmental Influences, Genetics, Prereading Experience