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Direct linkWillcutt, Erik G.; McGrath, Lauren M.; Pennington, Bruce F.; Keenan, Janice M.; DeFries, John C.; Olson, Richard K.; Wadsworth, Sally J. – New Directions for Child and Adolescent Development, 2019
Current definitions of specific learning disability (SLD) identify a heterogeneous population that includes individuals with weaknesses in reading, math, or writing, and these academic difficulties often co-occur in many of the same individuals. The Colorado Learning Disabilities Research Center (CLDRC) is an interdisciplinary, multisite research…
Descriptors: Comorbidity, Learning Disabilities, Twins, Reading Difficulties
Christopher, Micaela E.; Hulslander, Jacqueline; Byrne, Brian; Samuelsson, Stefan; Keenan, Janice M.; Pennington, Bruce; DeFries, John C.; Wadsworth, Sally J.; Willcutt, Erik; Olson, Richard K. – Child Development, 2015
The present study explored the environmental and genetic etiologies of the longitudinal relations between prereading skills and reading and spelling. Twin pairs (n = 489) were assessed before kindergarten (M = 4.9 years), post-first grade (M = 7.4 years), and post-fourth grade (M = 10.4 years). Genetic influences on five prereading skills (print…
Descriptors: Genetics, Longitudinal Studies, Reading Comprehension, Environmental Influences
Olson, Richard K.; Hulslander, Jacqueline; Christopher, Micaela; Keenan, Janice M.; Wadsworth, Sally J.; Willcutt, Erik G.; Pennington, Bruce F.; DeFries, John C. – Annals of Dyslexia, 2013
Identical and fraternal twins (N = 540, age 8 to 18 years) were tested on three different measures of writing (Woodcock-Johnson III Tests of Achievement--Writing Samples and Writing Fluency; Handwriting Copy from the Group Diagnostic Reading and Aptitude Achievement Tests), three different language skills (phonological awareness, rapid naming, and…
Descriptors: Measurement, Achievement Tests, Genetics, Word Recognition
Fujisawa, Keiko K.; Wadsworth, Sally J.; Kakihana, Shinichiro; Olson, Richard K.; DeFries, John C.; Byrne, Brian; Ando, Juko – Learning and Individual Differences, 2013
This first Japanese twin study of early literacy development investigated the extent to which genetic and environmental factors influence individual differences in prereading skills in 238 pairs of twins at 42 months of age. Twin pairs were individually tested on measures of phonological awareness, "kana" letter name/sound knowledge,…
Descriptors: Twins, Preschool Children, Emergent Literacy, Early Reading
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
Betjemann, Rebecca S.; Keenan, Janice M.; Olson, Richard K.; DeFries, John C. – Scientific Studies of Reading, 2011
Does the choice of test for assessing reading comprehension influence the outcome of genetic analyses? A twin design compared two types of reading comprehension tests classified as primarily associated with word decoding (RC-D) or listening comprehension (RC-LC). For both types of tests, the overall genetic influence is high and nearly identical.…
Descriptors: Reading Comprehension, Listening Comprehension, Siblings, Genetics
Selzam, Saskia; Dale, Philip S.; Wagner, Richard K.; DeFries, John C.; Cederlöf, Martin; O'Reilly, Paul F.; Krapohl, Eva; Plomin, Robert – Scientific Studies of Reading, 2017
It is now possible to create individual-specific genetic scores, called genome-wide polygenic scores (GPS). We used a GPS for years of education ("EduYears") to predict reading performance assessed at UK National Curriculum Key Stages 1 (age 7), 2 (age 12) and 3 (age 14) and on reading tests administered at ages 7 and 12 in a UK sample…
Descriptors: Genetics, Biological Sciences, Scores, Prediction
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
Astrom, Raven L.; Wadsworth, Sally J.; Olson, Richard K.; Willcutt, Erik G.; DeFries, John C. – Learning and Individual Differences, 2012
Reading performance data from 254 pairs of identical (MZ) and 420 pairs of fraternal (DZ) twins, 8.0 to 20.0 years of age, were subjected to multiple regression analyses. An extension of the DeFries-Fulker (DF) analysis (DeFries & Fulker, 1985, 1988) that facilitated inclusion of data from 303 of their nontwin siblings was employed. In addition to…
Descriptors: Reading Difficulties, Twins, Genetics, Environmental Influences
Friedman, Naomi P.; Miyake, Akira; Young, Susan E.; DeFries, John C.; Corley, Robin P.; Hewitt, John K. – Journal of Experimental Psychology: General, 2008
Recent psychological and neuropsychological research suggests that executive functions--the cognitive control processes that regulate thought and action--are multifaceted and that different types of executive functions are correlated but separable. The present multivariate twin study of 3 executive functions (inhibiting dominant responses,…
Descriptors: Genetics, Metacognition, Memory, Psychology
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
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
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
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
Wadsworth, Sally J.; DeFries, John C.; Olson, Richard K.; Willcutt, Erik G. – Annals of Dyslexia, 2007
The primary objectives of the present study are to introduce the Colorado Longitudinal Twin Study of Reading Disability, the first longitudinal twin study in which subjects have been specifically selected for having a history of reading difficulties, and to present some initial assessments of the stability of reading performance and cognitive…
Descriptors: Reading Difficulties, Twins, Genetics, Cognitive Ability
