Whether boys are more vulnerable than girls to reading disabilities (RD) is controversial. We review studies that were designed to minimize ascertainment bias in the selection of individuals with RD. These include population-based studies that identified children with RD by objective, unbiased methods and studies that examined the gender ratios among the affected relatives of those diagnosed with RD. We conclude that even when ascertainment biases are minimized, there is still a significant preponderance of boys with RD, although the gender ratio of the affected relatives of those with RD manifests the weakest male bias. Furthermore, we demonstrate that potentially confounding factors such as attentional or neurological problems, race, IQ, and severity of RD cannot account for the observed gender bias. We end with a clarion call to future researchers to (a) consider analyzing gender differences by means of more than one definition of RD, (b) compare gender ratios when boys and girls are ranked against the performance of their own gender as opposed to an average across genders, and (c) report group differences in variability and effect sizes of obtained gender ratios.
Get full access to this article
View all access options for this article.
References
1.
Abramowicz, H.K., & Richardson, S.A. (1975). Epidemiology of severe mental retardation in children. American Journal of Mental Deficiency, 80, 18—39.
2.
Ackerman, P., Dykman, R., & Oglesby, D. (1983). Sex differences in reading and attention disordered children with and without hyperkinesis. Journal of Learning Disabilities, 16, 407—415.
3.
Alcaron, M., DeFries, J., & Fulker, D. (1995). Etiology of individual differences in reading performance: A test of sex limitation. Behavior Genetics, 25, 17—23. American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., text revision). Washington, DC: Author.
4.
August, G.J., & Garfinkel, B.D. (1990). Co-morbidity of ADHD and reading disability among clinic-referred children. Journal of Abnormal Child Psychology, 18, 29—45.
5.
Bakwin, H. (1973). Reading disability in twins. Developmental Medicine and Child Neurology, 15, 184—187.
6.
Barclay, R.A. (1990). Attention deficit hyperactivity disorder: A handbook for diagnosis and treatment. New York: Guilford Press.
7.
Berger, M., Yule W., & Rutter, M. (1975). Attainment and adjustment in two geographical areas. II-The prevalence of specific reading retardation. British Journal of Psychiatry, 126, 510—519.
8.
Bisgaard, M.L., Eiberg, G., Moller, N., Niebuhr, E., & Mohr, J. (1987). Dyslexia and chromosome 15 heteromorphism: Negative lod score in a Danish material. Clinical Genetics, 32, 118—119.
9.
Carter, C.O. (1972). Sex-linkage and sex-limitation. In D. Ounsted & D. C. Taylor, Gender differences: Their ontogeny and significance (pp. 1—12). Edinburgh, UK: Churchill Livingstone.
10.
Childs, B. (1965). Genetic origin of some sex differences in human beings. Pediatrics, 35, 798—812.
11.
DeFries, J. (1989). Gender ratios in children with reading disability and their affected relatives: A commentary. Journal of Learning Disabilities, 22, 544—545.
12.
DeFries, J.C., & Baker, L. (1983). Colorado family reading study: Longitudinal analysis . Annals of Dyslexia, 33, 153—163.
13.
DeFries, J.C., & Decker, S.N. (1982). Genetic aspects of reading disability: A family study. In R. Malatesha & P. Aaron (Eds.), Reading disorders: Varieties and treatments (pp. 255—279). New York: Academic Press.
14.
DeFries, J., Fulker, D., & LaBuda, M. (1987). Evidence for a genetic etiology in reading disabilities of twins. Nature, 329, 537—539.
15.
DeFries, J., Gillis, J., & Wadsworth, S. (1993). Genes and gender: A twin study of reading disability. In A. M. Galaburda (Ed), Dyslexia and development: Neurobiological aspects of extra-ordinary brains (pp. 187—204). Cambridge, MA: Harvard University Press.
16.
DeFries, J., Olson, R., Pennington, R., & Smith, S. (1991). Colorado Reading Project: An update. In D. D. Duane & D. B. Gray (Ed), The reading brain: The biological basis of dyslexia (pp. 53—87). Parkton, MD: York Press.
17.
Feldman, E., Levin, B.E., Fleischmann, J., Jallad, B., Kushch, A., Gross-Glenn, K., et al. (1995). Gender differences in the severity of adult familial dyslexia. Reading and Writing: An Interdisciplinary Journal, 7, 155—161.
18.
Finucci, J.M., & Childs, B. (1981). Are there really more dyslexic boys than girls? In A. Ansora, N. Geschwind, A. Galaburda, M. Albert, & N. Gartrell (Eds.), Sex differences in dyslexia (pp. 1—9). Towson, MD: Orton Dyslexia Society.
19.
Finucci, J., Gottfredson, L., & Childs, B. (1985). A follow-up study of dyslexic boys. Annals of Dyslexia, 35, 117—136.
20.
Finucci, J., Isaacs, S., Whitehouse, C., & Childs, B. (1982). Empirical validation of reading and spelling quotients . Developmental Medicine and Child Neurology, 24, 733—744.
21.
Flannery, K.A., & Liederman, J. (1996). A reexamination of the sex ratios of families with a neurodevelopmentally disordered child. Journal of Child Psychology and Psychiatry, 37, 621—623.
22.
Flannery, K., Liederman, J., Daly, L., & Schultz, J. (2000). Male prevalence for reading disability is found in large sample of Black and White children free from ascertainment bias. Journal of the International Neuropsychological Society, 6, 433— 442.
23.
Fletcher, J.M., Francis, D.J., Rourke, B.P., Shaywitz, S.E., & Shaywitz, B.A. (1992). The validity of discrepancy-based definitions of reading disabilities. Journal of Learning Disabilities , 25, 551—61.
24.
Flynn, J.M., & Rahbar, M.H. (1994). Prevalence of reading failure in boys compared with girls. Psychology in the Schools, 31(1), 66—71.
25.
Galaburda, A. (1997, January). The toxicity of plasticity. Paper presented at the Veterans' Administration Medical Center, Jamaica Plain, MA.
26.
Geschwind, N., & Galaburda, A.M. (1985a). Cerebral lateralization: Biological mechanisms, associations, and pathology: I. A hypothesis and a program for research. Archives ofNeurology, 42, 428—459.
27.
Geschwind, N., & Galaburda, A.M. (1985b). Cerebral lateralization: Biological mechanisms, associations, and pathology: II. A hypothesis and a program for research. Archives ofNeurology, 42, 521—552.
28.
Geschwind, N., & Galaburda, A.M. (1985c). Cerebral lateralization: Biological mechanisms, associations, and pathology: III. A hypothesis and a program for research. Archives ofNeurology, 42, 634—654.
29.
Gilger, J.W. (1991). Differential assortive mating found for academic and demographic variables as a function of time assessment. BehaviorGenetics, 21, 131—158.
30.
Gualtieri, T., & Hicks, R.E. (1985). An immunoreactive theory of selective male affliction . The Behavioral and Brain Sciences, 8, 427—441.
31.
Hallgren, B. (1950). Specific dyslexia (congenital word-blindness): A clinical and genetic study. Acta Psychiatrica et Neurologica , Supplement, 65, 1—287.
32.
Ho, H., & Decker, S. (1988). Cognitive resemblance in reading-disabled twins . Developmental Medicine and Child Neurology, 30, 99—107.
33.
James, W.H. (1987). The human sex ratio. Part 1: A review of the literature . Human Biology, 59, 721—752.
34.
James, W.H. (1992). The sex ratios of dyslexic children and their sibs. Developmental Medicine and Child Neurology, 34, 530—533.
35.
Jorm, A., Share, D., Matthews, R., & MacLean, R. (1986). Behavior problems in specific reading retarded and general reading backwards children: A longitudinal study. Journal of Child Psychology and Psychiatry, 27, 33—43.
36.
Kantrowitz, L., Liederman, J., Belmonte, P., & Reich, L. (2004). Familial factors in the incidence of reading disability . Manuscript in preparation.
37.
Katusic, S.K., Colligan, R.C., Barbaresi, W.J., Schaid, D.J., & Jacobsen, S.J. (2001). Incidence of reading disability in a population-based birth cohort, 1976—1982, Rochester, Minn. Mayo Clinic Proceedings, 76, 1075—1077.
38.
Levine, S.C., Huttenlocher, J., Taylor, A., & Langrock, A. (1999). Early sex differences in spatial skill. Developmental Psychology, 35, 940—949.
39.
Lewis, B.A. (1992). Pedigree analysis of children with phonology disorders . Journal of Learning Disabilities, 25, 586—597.
40.
Lewis, C., Hitch, G., & Walker, P. (1993). The prevalence of specific arithmetic difficulties and specific reading difficulties in 9-to 10-year-old boys and girls. Journal of Child Psychology, 35, 283—292.
41.
Liederman, J., & Flannery, K.A. (1995). The sex ratios of families with a neurodevelopmentally disordered child. Journal of Child Psychology and Psychiatry, 36, 511— 517.
42.
Lovell, K., Shapton, D., & Warren, N. (1964). A study of some cognitive and other disabilities in backward readers of average intelligence as assessed by a non-verbal test . British Journal of Educational Psychology, 34, 58—64.
43.
Lubs, H., Rabin, M., Feldman, E., Jallad, B., Kushch, A., & Gross-Glenn, K. (1993). Familial dyslexia: Genetic and medical findings in eleven three-generation families. Annals of Dyslexia, 43, 45—60.
44.
Lykken, D., Tellegen, A., & DeRubeis, R. (1978). Volunteer bias in twin research: The rule of two-thirds . Social Biology, 25, 1—9.
45.
Mercer, C.D. (1991). Students with learning disabilities. New York: Macmillan.
46.
Miles, T.R., Haslum, M.N., & Wheeler, T.J. (1998). Gender ratio in dyslexia. Annals of Dyslexia, 48, 27—55.
47.
Mirkin, P. (1982). Direct and repeated measurement of academic skills: An alternative to traditional screening, referral, and identification of learning disabled students [Report No. IRLD-RR-75]. Washington, DC: Office of Special Education and Rehabilitative Services. (ERIC Document Reproduction Service No. ED224191)
48.
Nichols, T., & Chen, T. (1981). Minimal brain dysfunction: A propsective study . Hillsdale, NJ: Erlbaum.
49.
Omenn, G.S., & Weber, B.A. (1978). Dyslexia: Search for phenotypic and genetic heterogeneity . American Journal of Medical Genetics, 1, 33—342.
50.
Ounsted, D., & Taylor, D.C. (1972). Gender differences: Their ontogeny and significance. Edinburgh, UK: Churchill Livingstone.
Pennington, B., Gilger, J., Olson, R., & DeFries, J. (1992). The external validity of age- versus IQ-discrepancy definitions of reading disability: Lessons from a twin study. Journal of Learning Disabilities, 25, 562—573.
53.
Pennington, B., Gilger, J., Pauls, D., Smith, S., Smith, S.D., & DeFries, J. (1991). Evidence for major gene transmission of developmental dyslexia. Journal of theAmerican Medical Association, 266, 1527—1534.
54.
Richardson, A.J. (1994). Dyslexia, handedness, and syndromes of psychosis-proneness. International Journal ofPsychophysiology, 18, 251—263.
55.
Rutter, M., & Yule, W. (1975). The concept of specific reading retardation. Child Psychology andPsychiatry, 16, 181—197.
56.
Schulte-Korne, G., Deimel, W., Muller, K., Gutenbrunner, C., & Remschmidt, H. (1996). Familial aggregation of spelling disability. Journal of Child Psychology and Psychiatry , 37, 817—822.
57.
Share, D.L., & Silva, P.A. (2003). Gender bias in IQ-discrepancy and post-discrepancy definitions of reading disability. Journal of Learning Disabilities , 36, 4—14.
58.
Shaywitz, B., Shaywitz, S., Pugh, K., Constable, R., Skudlarski, P., Fulbright, R., et al. (1995). Sex differences in functional organization of the brain for language. Nature, 373, 607—609.
59.
Shaywitz, S.E. (1996). Dyslexia. Scientific American , 275, 98—104.
60.
Shaywitz, S.E. (1998). Dyslexia. The New England Journal of Medicine, 338, 307—312.
61.
Shaywitz, S.E., Shaywitz, B.A., Fletcher, J.M., & Escobar, M.D. (1990). Prevalence of reading disability in boys and girls. Results of the Connecticut Longitudinal Study. Journal of theAmerican Medical Association, 264, 998—1002.
62.
Siegel, L.S. (1989). IQ is irrelevant to the definition of learning disability. Canadian Journal of Psychology, 42, 201—215.
63.
Siegel, L.S. (1992). An evaluation of the discrepancy definition of dyslexia. Journal of Learning Disabilities, 25, 618—629.
64.
Singer, J., Westphal, M., & Niswander, K. (1968). Sex differences in the incidence of neonatal abnormalities and abnormal performance in early childhood. Child Development , 39, 103—112.
65.
Smith, S. (1992). Familial patterns of learning disabilities. Annals of Dyslexia, 42, 143—158.
66.
Smith, S., Kimberling, W., Pennington, B., & Lubs, H. (1983). Specific reading disability: Identification of an inherited form through linkage analysis. Science, 219, 1345—1347.
67.
Smith, S.D., Pennington, B.F., Kimberling, W.J., & Ing, P.S. (1990). Familial dyslexia: Use of genetic linkage data to define subtypes. Journal of the American Academy of Child and Adolescent Psychiatry, 29, 204— 213.
68.
Stanovich, K.E. (1991). Discrepancy definitions of reading disability: Has intelligence led us astray?Reading Research Quarterly , 26, 7—29.
69.
Stevenson, J. (1992). Identifying sex differences in reading disability: Lessons from a twin study. Reading and Writing: An Interdisciplinary Journal, 4, 307—326.
70.
Tallal, P., Ross, R., & Curtiss, S. (1989). Unexpected sex-ratios in families of language/ learning impaired children. Neuropsychologia,7, 987—998.
71.
Vogel, S. (1990). Gender differences in intelligence, language, visual—motor abilities, and academic achievement in students with learning disabilities: A review of the literature. Journal of Learning Disabilities, 23, 44—52.
72.
Vogler, G., DeFries, J., & Decker, S. (1985). Family history as an indicator of risk for reading disability. Journal of Learning Disabilities, 18, 419—421.
73.
Willcutt, E.G., Pennington, B.F., Smith, S.D., Cardon, L.R., Grayan, 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, 260—268.
74.
Wolff, P., & Melngallis, I. (1994). Family patterns of developmental dyslexia: Clinical findings. American Journal of Medical Genetics , 54, 122—131.
75.
Yule, W., Rutter, M., Berger, M., & Thompson, J. (1974). Over- and under-achievement in reading distribution in the general population. British Journal of Educational Psychology, 44, 1—12.
