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Gene × Environment interactions in speech sound disorder predict language and preliteracy outcomes

  • Lauren M. McGrath (a1), Bruce F. Pennington (a1), Erik G. Willcutt (a2), Richard Boada (a3), Lawrence D. Shriberg (a4) and Shelley D. Smith (a5)...

Abstract

Few studies have investigated the role of gene × environment interactions (G × E) in speech, language, and literacy disorders. Currently, there are two theoretical models, the diathesis–stress model and the bioecological model, that make opposite predictions about the expected direction of G × E, because environmental risk factors may either strengthen or weaken the effect of genes on phenotypes. The purpose of the current study was to test for G × E at two speech sound disorder and reading disability linkage peaks using a sib-pair linkage design and continuous measures of socioeconomic status, home language/literacy environment, and number of ear infections. The interactions were tested using composite speech, language, and preliteracy phenotypes and previously identified linkage peaks on 6p22 and 15q21. Results showed five G × E at both the 6p22 and 15q21 locations across several phenotypes and environmental measures. Four of the five interactions were consistent with the bioecological model of G × E. Each of these four interactions involved environmental measures of the home language/literacy environment. The only interaction that was consistent with the diathesis–stress model was one involving the number of ear infections as the environmental risk variable. The direction of these interactions and possible interpretations are explored in the discussion.

Copyright

Corresponding author

Address correspondence and reprint requests to: Lauren M. McGrath, University of Denver, Department of Psychology, Frontier Hall, 2155 S. Race Street, Denver, CO 80209; E-mail: lmcgrath@du.edu.

References

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Abecasis, G. R., Cherny, S. S., Cookson, W. O., & Cardon, L. R. (2002). Merlin—Rapid analysis of dense genetic maps using sparse gene flow trees. Nature Genetics, 30, 97101.
Abecasis, G. R., & Wigginton, J. E. (2005). Handling marker–marker linkage disequilibrium: Pedigree analysis with clustered markers. American Journal of Human Genetics, 77, 754767.
Aiken, L. S., & West, S. G. (1991). Multiple regression: Testing and interpreting interactions. Newbury Park, CA: Sage.
Allen, L., Cipielewski, J., & Stanovich, K. E. (1992). Multiple indicators of children's reading habits and attitudes: Construct validity and cognitive correlates. Journal of Educational Psychology, 84, 489503.
Asbury, K., Wachs, T. D., & Plomin, R. (2005). Environmental moderators of genetic influence on verbal and nonverbal abilities in early childhood. Intelligence, 33, 643661.
Bartlett, C. W., Flax, J. F., Logue, M. W., Vieland, V. J., Bassett, A. S., Tallal, P., et al. (2002). A major susceptibility locus for specific language impairment is located on 13q21. American Journal of Human Genetics, 71, 4555.
Beitchman, J. H., Nair, R., Clegg, M., Ferguson, B., & Patel, P. G. (1986). Prevalence of psychiatric disorders in children with speech and language disorders. Journal of the American Academy of Child & Adolescent Psychiatry, 25, 528535.
Bellini, G., Bravaccio, C., Calamoneri, F., Donatella Cocuzza, M., Fiorillo, P., Gagliano, A., et al. (2005). No evidence for association between dyslexia and dyx1c1 functional variants in a group of children and adolescents from southern Italy. Journal of Molecular Neuroscience, 27, 311314.
Bird, J., & Bishop, D. (1992). Perception and awareness of phonemes in phonologically impaired children. European Journal of Disorders of Communication, 27, 289311.
Bishop, D. V. M. (1997a). Pre- and perinatal hazards and family background in children with specific language impairments: A study of twins. Brain and Language, 56, 126.
Bishop, D. V. M. (1997b). Uncommon understanding: Development and disorders of language comprehension in children. Cambridge: Psychology Press.
Bishop, D. V. M., & Adams, C. (1990). A prospective study of the relationship between specific language impairment, phonological disorders and reading retardation. Journal of Child Psychology and Psychiatry, 31, 10271050.
Bradley, R. H. (1993). Children's home environments, health, behavior, and intervention efforts: A review using the home inventory as a marker measure. Genetic, Social, and General Psychology Monographs, 119, 437490.
Bronfenbrenner, U., & Ceci, S. J. (1994). Nature–nurture reconceptualized in developmental perspective: A bioecological model. Psychological Review, 101, 568586.
Bus, A. G., van IJzendoorn, M. H., & Pellegrini, A. D. (1995). Joint book reading makes for success in learning to read: A meta-analysis on intergenerational transmission of literacy. Review of Educational Research, 65, 121.
Byrne, B., Delaland, C., Fielding-Barnsley, R., Quain, P., Samuelsson, S., Hoien, T., et al. (2002). Longitudinal twin study of early reading development in three countries: Preliminary results. Annals of Dyslexia, 52, 49.
Byrne, B., Wadsworth, S., Corley, R., Samuelsson, S., Quain, P., DeFries, J. C., et al. (2005). Longitudinal twin study of early literacy development: Preschool and kindergarten phases. Scientific Studies of Reading, 9, 219.
Cadoret, R. J., Yates, W. R., Troughton, E., Woodworth, G., & Stewart, M. A. (1995). Genetic–environmental interaction in the genesis of aggressivity and conduct disorders. Archives of General Psychiatry, 52, 916924.
Caldwell, B. M., & Bradley, R. H. (1984). Home Observation for Measurement of the Environment. Little Rock, AR: University of Arkansas at Little Rock.
Campbell, T. F., Dollaghan, C. A., Rockette, H. E., Paradise, J. L., Feldman, H. M., Shriberg, L. D., et al. (2003). Risk factors for speech delay of unknown origin in 3-year-old children. Child Development, 74, 346357.
Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., et al. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297, 851854.
Caspi, A., Sugden, K., Moffitt, T. E., Taylor, A., Craig, I. W., Harrington, H., et al. (2003). Influence of life stress on depression: Moderation by a polymorphism in the 5-HTT gene. Science, 301, 386389.
Colledge, E., Bishop, D. V. M., Koeppen-Schomerus, G., Price, T. S., Happe, F. G., Eley, T. C., et al. (2002). The structure of language abilities at 4 years: A twin study. Developmental Psychology, 38, 749757.
Cope, N., Harold, D., Hill, G., Moskvina, V., Stevenson, J., Holmans, P., et al. (2005). Strong evidence that KIAA0319 on chromosome 6p is a susceptibility gene for developmental dyslexia. American Journal of Human Genetics, 76, 581591.
Cope, N., Hill, G., van den Bree, M., Harold, D., Moskvina, V., Green, E. K., et al. (2005). No support for association between dyslexia susceptibility 1 candidate 1 and developmental dyslexia. Molecular Psychiatry, 10, 237238.
Deffenbacher, K. E., Kenyon, J. B., Hoover, D. M., Olson, R. K., Pennington, B. F., DeFries, J. C., et al. (2004). Refinement of the 6p21.3 quantitative trait locus influencing dyslexia: Linkage and association analyses. Human Genetics, 115, 128138.
DeFries, J. C., & Fulker, D. W. (1985). Multiple regression analysis of twin data. Behavior Genetics, 15, 467473.
DeFries, J. C., & Fulker, D. W. (1988). Multiple regression analysis of twin data: Etiology of deviant scores versus individual differences. Acta Geneticae Medicae et Gemellologiae, 37, 205216.
DeFries, J. C., Fulker, D. W., & LaBuda, M. C. (1987). Evidence for a genetic aetiology in reading disability of twins. Nature, 329, 537539.
DeFries, J. C., & Gillis, J. J. (1991). Etiology of reading deficits in learning disabilities: Quantitative genetic analysis. In Obrzut, J. E. & Hynd, G. W. (Eds.), Neuropsychological foundations of learning disabilities: A handbook of issues, methods, and practice (pp. 2947). San Diego, CA: Academic Press.
Dollaghan, C., & Campbell, T. F. (1998). Nonword repetition and child language impairment. Journal of Speech, Language, and Hearing Research, 41, 11361146.
Dunning, D. B., Mason, J. M., & Stewart, J. P. (1994). Reading to preschoolers: A response to Scarborough and Dorich (1994) and recommendations for future research. Developmental Review, 14, 324339.
Eley, T. C., Sugden, K., Corsico, A., Gregory, A. M., Sham, P., McGuffin, P., et al. (2004). Gene–environment interaction analysis of serotonin system markers with adolescent depression. Molecular Psychiatry, 9, 908915.
Elliott, C. D. (1990). Differential Ability Scales. San Antonio, TX: Psychological Corporation.
Faraone, S. V., Tsuang, M. T., & Tsuang, D. W. (1999). Genetics of mental disorders: A guide for students, clinicians, and researchers. New York: Guilford Press.
Feldman, H. M., Dollaghan, C. A., Campbell, T. F., Colborn, D. K., Janosky, J., Kurs-Lasky, M., et al. (2003). Parent-reported language skills in relation to otitis media during the first 3 years of life. Journal of Speech, Language, and Hearing Research, 46, 273287.
Felsenfeld, S., McGue, M., & Broen, P. A. (1995). Familial aggregation of phonological disorders: Results from a 28-year follow-up. Journal of Speech and Hearing Research, 38, 10911107.
Fisher, S. E., & DeFries, J. C. (2002). Developmental dyslexia: Genetic dissection of a complex cognitive trait. Nature Reviews Neuroscience, 3, 767780.
Fisher, S. E., & Francks, C. (2006). Genes, cognition and dyslexia: Learning to read the genome. Trends in Cognitive Sciences, 10, 250257.
Francks, C., Paracchini, S., Smith, S. D., Richardson, A. J., Scerri, T. S., Cardon, L. R., et al. (2004). A 77-kilobase region of chromosome 6p22.2 is associated with dyslexia in families from the United Kingdom and from the United States. American Journal of Human Genetics, 75, 10461058.
Fulker, D. W., Cardon, L. R., DeFries, J. C., Kimberling, W. J., Pennington, B. F., & Smith, S. D. (1991). Multiple regression analysis of sib-pair data on reading to detect quantitative trait loci. Reading & Writing, 3, 299313.
Gathercole, S. E., & Baddeley, A. D. (1990). Phonological memory deficits in language disordered children: Is there a causal connection? Journal of Memory and Language, 29, 336.
Gilger, J. W., Ho, H.-Z., Whipple, A. D., & Spitz, R. (2001). Genotype–environment correlations for language-related abilities. Journal of Learning Disabilities, 34, 492502.
Goldman, R., & Fristoe, M. (1986). The Goldman Fristoe Test of Articulation. Circle Pine, MN: American Guidance Service.
Gottesman, I. (1963). Genetic aspects of intelligent behavior. In Ellis, N. (Ed.), The handbook of mental deficiency: Psychological theory and research (pp. 253296). New York: McGraw–Hill.
Grigorenko, E. L. (2005). The inherent complexities of gene–environment interactions. Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 60, 5364.
Grigorenko, E. L., Wood, F. B., Meyer, M. S., Hart, L. A., Speed, W. C., Shuster, A., et al. (1997). Susceptibility loci for distinct components of developmental dyslexia on chromosomes 6 and 15. American Journal of Human Genetics, 60, 2739.
Hart, B., & Risley, T. R. (1992). American parenting of language-learning children: Persisting differences in family–child interactions observed in natural home environments. Developmental Psychology, 28, 10961105.
Hayden, D. A., & Square, P. (1997). The Verbal Motor Production Assessment for Children (VMPAC). San Antonio, TX: Psychological Corporation.
Holm, V. A., & Kunze, L. H. (1969). Effect of chronic otitis media on language and speech development. Pediatrics, 43, 833839.
Kashy, D. A., Kenny, D. A., Reis, H. T., & Judd, C. M. (2000). The analysis of data from dyads and groups. In Reis, H. T. (Ed.), Handbook of research methods in social and personality psychology (p. 451). New York: Cambridge University Press.
Kendler, K. S., & Eaves, L. J. (1986). Models for the joint effect of genotype and environment on liability to psychiatric illness. American Journal of Psychiatry, 143, 279289.
Kline, R. B. (2005). Principles and practice of structural equation modeling (2nd ed.). New York: Guilford Press.
Kohler, H. P., & Rodgers, J. L. (2001). DF-analyses of heritability with double-entry twin data: Asymptotic standard errors and efficient estimation. Behavior Genetics, 31, 179191.
Kong, X., Murphy, K., Raj, T., He, C., White, P. S., & Matise, T. C. (2004). A combined linkage-physical map of the human genome. American Journal of Human Genetics, 75, 11431148.
Kovas, Y., Hayiou-Thomas, M. E., Oliver, B., Dale, P. S., Bishop, D. V. M., & Plomin, R. (2005). Genetic influences in different aspects of language development: The etiology of language skills in 4.5-year-old twins. Child Development, 76, 632651.
Kremen, W. S., Jacobson, K. C., Xian, H., Eisen, S. A., Waterman, B., Toomey, R., et al. (2005). Heritability of word recognition in middle-aged men varies as a function of parental education. Behavior Genetics, 35, 417433.
Kruglyak, L., Daly, M. J., Reeve-Daly, M. P., & Lander, E. S. (1996). Parametric and nonparametric linkage analysis: A unified multipoint approach. American Journal of Human Genetics, 58, 13471363.
Lander, E., & Kruglyak, L. (1995). Genetic dissection of complex traits: Guidelines for interpreting and reporting linkage results. Nature Genetics, 11, 241247.
Lewis, B. A., Shriberg, L. D., Freebairn, L. A., Hansen, A. J., Stein, C. M., Taylor, H. G., et al. (in press). The genetic bases of speech sound disorders: Evidence from spoken and written language. Journal of Speech, Language, and Hearing Research.
Lewis, B. A., & Thompson, L. A. (1992). A study of developmental speech and language disorders in twins. Journal of Speech and Hearing Research, 35, 10861094.
Lewontin, R. (1970). Race and intelligence. Bulletin of the Atomic Scientists, 26, 28.
Lonigan, C. J. (1994). Reading to preschoolers exposed: Is the emperor really naked? Developmental Review, 14, 303323.
Marino, C., Giorda, R., Luisa Lorusso, M., Vanzin, L., Salandi, N., Nobile, M., et al. (2005). A family-based association study does not support dyx1c1 on 15q21.3 as a candidate gene in developmental dyslexia. European Journal of Human Genetics, 13, 491499.
McGrath, L. M., Smith, S. D., & Pennington, B. F. (2006). Breakthroughs in the search for dyslexia candidate genes. Trends in Molecular Medicine, 12, 333341.
Meng, H., Hager, K., Held, M., Page, G. P., Olson, R. K., Pennington, B. F., et al. (2005). Tdt-association analysis of ekn1 and dyslexia in a Colorado twin cohort. Human Genetics, 118, 8790.
Meng, H., Smith, S. D., Hager, K., Held, M., Liu, J., Olson, R. K., et al. (2005). DCDC2 is associated with reading disability and modulates neuronal development in the brain. Proceedings of the National Academy of Sciences of the USA, 102, 1705317058.
Miscimarra, L., Stein, C., Millard, C., Kluge, A., Cartier, K., Freebairn, L., et al. (in press). Further evidence of pleiotropy influencing speech and language: Analysis of the dyx8 region. Human Heredity.
Neisser, U., Boodoo, G., Bouchard, T. J. Jr., Boykin, A. W., Brody, N., Ceci, S. J., et al. (1996). Intelligence: Knowns and unknowns. American Psychologist, 51, 77.
Newcomer, P. L., & Hammill, D. D. (1997). Test of Language Development: Primary (TOLD-P:3). Austin, TX: Pro-Ed.
Nopola-Hemmi, J., Myllyluoma, B., Haltia, T., Taipale, M., Ollikainen, V., Ahonen, T., et al. (2001). A dominant gene for developmental dyslexia on chromosome 3. Journal of Medical Genetics, 38, 658664.
O'Connor, T. G., Caspi, A., Defries, J. C., & Plomin, R. (2003). Genotype–environment interaction in children's adjustment to parental separation. Journal of Child Psychology & Psychiatry, 44, 849856.
Paracchini, S., Thomas, A., Castro, S., Lai, C., Paramasivam, M., Wang, Y., et al. (2006). The chromosome 6p22 haplotype associated with dyslexia reduces the expression of KIAA0319, a novel gene involved in neuronal migration. Human Molecular Genetics.
Paradise, J. L., Rockette, H. E., Colborn, D. K., Bernard, B. S., Smith, C. G., Kurs-Lasky, M., et al. (1997). Otitis media in 2253 Pittsburgh-area infants: Prevalence and risk factors during the first two years of life. Pediatrics, 99, 318333.
Pennington, B. F. (1997). Using genetics to dissect cognition. American Journal of Human Genetics, 60, 1316.
Pennington, B. F. (2002). The development of psychopathology: Nature and nurture. New York: Guilford Press.
Phillips, B. M., & Lonigan, C. J. (2005). Social correlates of emergent literacy. In Snowling, M. J. & Hulme, C. (Eds.), The science of reading: A handbook (pp. 173187). Malden, MA: Blackwell.
Plomin, R., DeFries, J. C., McClearn, G. E., & Rutter, M. (1997). Behavioral genetics (3rd ed.). New York: W. H. Freeman.
Purcell, S. (2002). Variance components models for gene–environment interaction in twin analysis. Twin Research, 5, 554571.
Raitano, N. A., Pennington, B. F., Tunick, R. A., Boada, R., & Shriberg, L. D. (2004). Pre-literacy skills of subgroups of children with speech sound disorders. Journal of Child Psychology and Psychiatry, 45, 821835.
Rende, R., & Plomin, R. (1992). Diathesis–stress models of psychopathology: A quantitative genetic perspective. Applied and Preventive Psychology, 1, 177182.
Roberts, J., Hunter, L., Gravel, J., Rosenfeld, R., Berman, S., Haggard, M., et al. (2004). Otitis media, hearing loss, and language learning: Controversies and current research. Journal of Developmental and Behavioral Pediatrics, 25, 110122.
Rodgers, J. L., & Kohler, H. P. (2005). Reformulating and simplifying the df analysis model. Behavior Genetics, 35, 211217.
Rowe, D. C., Jacobson, K. C., & Van den Oord, E. J. (1999). Genetic and environmental influences on vocabulary IQ: Parental education level as moderator. Child Development, 70, 11511162.
Rutter, M. (1983). Statistical and personal interactions: Facets and perspectives. In Magnusson, D. & Allen, V. (Eds.), Human development: An interactional perspective (pp. 295319). New York: Academic Press.
Rutter, M., Dunn, J., Plomin, R., Simonoff, E., Pickles, A., Maughan, B., et al. (1997). Integrating nature and nurture: Implications of person–environment correlations and interactions for developmental psychopathology. Development and Psychopathology, 9, 335364.
Rutter, M., Moffitt, T. E., & Caspi, A. (2006). Gene–environment interplay and psychopathology: Multiple varieties but real effects. Journal of Child Psychology and Psychiatry, 47, 226261.
Samuelsson, S., Byrne, B., Quain, P., Wadsworth, S., Corley, R., DeFries, J. C., et al. (2005). Environmental and genetic influences on prereading skills in Australia, Scandinavia, and the United States. Journal of Educational Psychology, 97, 705722.
Scarborough, H. S. (1990). Very early language deficits in dyslexic children. Child Development, 61, 17281743.
Scarborough, H. S., & Dobrich, W. (1994a). Another look at parent–preschooler bookreading: How naked is the emperor? A response to Lonigan (1994) and Dunning, Mason, and Stewart (1994). Developmental Review, 14, 340347.
Scarborough, H. S., & Dobrich, W. (1994b). On the efficacy of reading to preschoolers. Developmental Review, 14, 245302.
Scarr, S. (1992). Developmental theories for the 1990s: Development and individual differences. Child Development, 63, 119.
Scarr, S., & McCartney, K. (1983). How people make their own environments: A theory of genotype–environment effects. Child Development, 54, 424435.
Scerri, T. S., Fisher, S. E., Francks, C., MacPhie, I. L., Paracchini, S., Richardson, A. J., et al. (2004). Putative functional alleles of dyx1c1 are not associated with dyslexia susceptibility in a large sample of sibling pairs from the UK. Journal of Medical Genetics, 41, 853857.
Schumacher, J., Anthoni, H., Dahdouh, F., Konig, I. R., Hillmer, A. M., Kluck, N., et al. (2006). Strong genetic evidence of DCDC2 as a susceptibility gene for dyslexia. American Journal of Human Genetics, 78, 5262.
Sham, P. C., Purcell, S., Cherny, S. S., & Abecasis, G. R. (2002). Powerful regression-based quantitative-trait linkage analysis of general pedigrees. American Journal of Human Genetics, 71, 238253.
Shanahan, M. J., & Hofer, S. M. (2005). Social context in gene–environment interactions: Retrospect and prospect. Journal of Gerontology Series B: Psychological Sciences and Social Sciences, 60, 6576.
Shriberg, L. D. (2003). Diagnostic markers for child speech-sound disorders: Introductory comments. Clinical Linguistics and Phonetics, 17, 501505.
Shriberg, L. D., Austin, D., Lewis, B. A., McSweeny, J. L., & Wilson, D. L. (1997a). The percentage of consonants correct (PCC) metric: Extensions and reliability data. Journal of Speech, Language, and Hearing Research, 40, 708722.
Shriberg, L. D., Austin, D., Lewis, B. A., McSweeny, J. L., & Wilson, D. L. (1997b). The Speech Disorders Classification System (SDCS): Extensions and lifespan reference data. Journal of Speech, Language, and Hearing Research, 40, 723740.
Shriberg, L. D., Flipsen, P. Jr., Thielke, H., Kwiatkowski, J., Kertoy, M. K., Katcher, M. L., et al. (2000). Risk for speech disorder associated with early recurrent otitis media with effusion: Two retrospective studies. Journal of Speech, Language, and Hearing Research, 43, 7999.
Shriberg, L. D., Friel-Patti, S., Flipsen, P. Jr., & Brown, R. L. (2000). Otitis media, fluctuant hearing loss, and speech–language outcomes: A preliminary structural equation model. Journal of Speech, Language, and Hearing Research, 43, 100120.
Shriberg, L. D., Tomblin, J. B., & McSweeny, J. L. (1999). Prevalence of speech delay in 6-year-old children and comorbidity with language impairment. Journal of Speech, Language, and Hearing Research, 42, 14611481.
Silberg, J., Rutter, M., Neale, M., & Eaves, L. (2001). Genetic moderation of environmental risk for depression and anxiety in adolescent girls. British Journal of Psychiatry, 179, 116121.
SLI Consortium. (2002). A genomewide scan identifies two novel loci involved in specific language impairment. American Journal of Human Genetics, 70, 384398.
SLI Consortium. (2004). Highly significant linkage to the sli1 locus in an expanded sample of individuals affected by specific language impairment. American Journal of Human Genetics, 74, 12251238.
Smith, S. D., Pennington, B. F., Boada, R., & Shriberg, L. D. (2005). Linkage of speech sound disorder to reading disability loci. Journal of Child Psychology and Psychiatry, 46, 10571066.
Stanovich, K. E., & West, R. F. (1989). Exposure to print and orthographic processing. Reading Research Quarterly, 24, 402433.
Stein, C. M., Millard, C., Kluge, A., Miscimarra, L. E., Cartier, K. C., Freebairn, L. A., et al. (2006). Speech sound disorder influenced by a locus in 15q14 region. Behavior Genetics, 36, 858868.
Stein, C. M., Schick, J. H., Gerry Taylor, H., Shriberg, L. D., Millard, C., Kundtz-Kluge, A., et al. (2004). Pleiotropic effects of a chromosome 3 locus on speech-sound disorder and reading. American Journal of Human Genetics, 74, 283297.
Stevenson, J., Pennington, B. F., Gilger, J. W., DeFries, J. C., & Gillis, J. J. (1993). Hyperactivity and spelling disability: Testing for shared genetic aetiology. Journal of Child Psychology and Psychiatry, 34, 11371152.
Tabachnick, B. G., & Fidell, L. S. (2001). Using multivariate statistics (4th ed.). Boston: Allyn & Bacon.
Taipale, M., Kaminen, N., Nopola-Hemmi, J., Haltia, T., Myllyluoma, B., Lyytinen, H., et al. (2003). A candidate gene for developmental dyslexia encodes a nuclear tetratricopeptide repeat domain protein dynamically regulated in brain. Proceedings of the National Academy of Sciences of the USA, 100, 1155311558.
Thorpe, K., Rutter, M., & Greenwood, R. (2003). Twins as a natural experiment to study the causes of mild language delay: II: Family interaction risk factors. Journal of Child Psychology and Psychiatry, 44, 342355.
Tomblin, J. B., & Buckwalter, P. R. (1998). Heritability of poor language achievement among twins. Journal of Speech, Language, and Hearing Research, 41, 188199.
Totsika, V., & Sylva, K. (2004). The Home Observation for Measurement of the Environment revisited. Child and Adolescent Mental Health, 9, 2535.
Treiman, R., Tincoff, R., Rodriguez, K., Mouzaki, A., & Francis, D. J. (1998). The foundations of literacy: Learning the sounds of letters. Child Development, 69, 15241540.
Turkheimer, E., Haley, A., Waldron, M., D'Onofrio, B., & Gottesman, II. (2003). Socioeconomic status modifies heritability of IQ in young children. Psychological Science, 14, 623628.
van den Oord, E. J., & Rowe, D. C. (1998). An examination of genotype–environment interactions for academic achievement in an U.S. National Longitudinal Survey. Intelligence, 25, 205228.
Wagner, R. K., Torgesen, J. K., & Rashotte, C. A. (1999). The Comprehensive Test of Phonological Processing (CTOPP). Austin, TX: Pro-Ed.
Wang, Y., Paramasivam, M., Thomas, A., Bai, J., Kaminen-Ahola, N., Kere, J., et al. (2006). Dyx1c1 functions in neuronal migration in developing neocortex. Neuroscience, 143, 515522.
Wechsler, D. (1992). Wechsler Individual Achievement Test (WIAT). San Antonio, TX: Psychological Corporation.
Wiederholt, J., & Bryant, B. R. (1992). Gray Oral Reading Test—III. Austin, TX: Psychological Corporation.
Wigg, K. G., Couto, J. M., Feng, Y., Anderson, B., Cate-Carter, T. D., Macciardi, F., et al. (2004). Support for ekn1 as the susceptibility locus for dyslexia on 15q21. Molecular Psychiatry, 9, 11111121.
Willcutt, E. G., & Pennington, B. F. (2000). Psychiatric comorbidity in children and adolescents with reading disability. Journal of Child Psychology and Psychiatry, 41, 10391048.
Willcutt, E. G., Pennington, B. F., Smith, S. D., Cardon, L. R., Gayan, J., Knopik, V. S., et al. (2002). Quantitative trait locus for reading disability on chromosome 6p is pleiotropic for attention-deficit/hyperactivity disorder. American Journal of Medical Genetics, 114, 260268.
Young, A. (1995). Genetic analysis system (Version 2.0) [Software]. Oxford: Oxford University.

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