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Etiology of Reading Difficulties as a Function of Gender and Severity
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Hawke, Jesse L.; Wadsworth, Sally J.; Olson, Richard K.; DeFries, John C. – Reading and Writing: An Interdisciplinary Journal, 2007
To test the hypothesis that the etiology of reading difficulties may differ for males and females in more severely impaired samples, reading performance data from monozygotic (MZ), same-sex dizygotic (DZ[subscript ss]), and opposite-sex dizygotic (DZ[subscript os]) twin pairs were analyzed using a model-fitting implementation of the DeFries-Fulker…
Descriptors: Severity (of Disability), Environmental Influences, Etiology, Genetics
Genetic and Environmental Influences on Prereading Skills and Early Reading and Spelling Development in the United States, Australia, and Scandinavia
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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
Genetic and Environmental Influences on Early Literacy
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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
Genetic and Environmental Influences on Reading and Listening Comprehension
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Keenan, Janice M.; Betjemann, Rebecca S.; Wadsworth, Sally J.; DeFries, John C.; Olson, Richard K. – Journal of Research in Reading, 2006
We report preliminary behaviour genetic analyses of reading and listening comprehension from The Colorado Learning Disabilities Research Center. Although the twin sample with these new measures is still of limited size, we find substantial, and significant, genetic influences on individual differences in both reading and listening comprehension.…
Descriptors: Environmental Influences, Word Recognition, Reading Comprehension, Listening Comprehension
Environmental and Genetic Influences on Prereading Skills in Australia, Scandinavia, and the United States
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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