Drake D. Duane
Defining Dyslexia
Arizona State University
reading natural human act hearing humans speak seeing hearing humans may read indeed every culture humankind literate inability read skill decoding written language childhood despite speech sight experience recognized near end 19th century disability initially termed congenital word blindness later developmental dyslexia dyslexia designation first applied loss reading skill brain insult1hinshelwood j wordblindness visual memorylancet 1895 2 15641570abstract scopus 60 google scholar 2morgan wp case congenital word blindnessbmj 1896 2 1378crossref pubmed scopus 305 google scholar 3berlin r eine besondere art der wortblindheit dyslexie verlag von jf bergmann wiesbaden germany1887google scholar current dsmiv nomenclature uses developmental reading disorder4american psychiatric association diagnostic statistical manual mental disorders 4th ed american psychiatric association washington dc1994google scholar icd9 classification accepts dyslexia reading disorder appropriate terms5world health organization international classification diseases ninth revision world health organization geneva switzerland1979google scholar resistance literacy occurs one thrust national institutes health specifically national institute child health human development nichd research effort entitled decade brain least 2 genomic sites altered pattern neural anatomic organization respects reminiscent first described epilepsy anomalous activation brain regions act reading characteristic weakness associating speech sounds graphemes rhymes suggest biological source involving perception speech brain mechanisms partially explain reading disability6grigorenko el wood fb meyer ms et alsusceptibility loci distinct components developmental dyslexia chromosomes 6 15am j hum genet 1997 60 2739pubmed google scholar 7galaburda sherman gf rosen gd aboitiz f geschwind n developmental dyslexia four consecutive patients cortical anomaliesann neurol 1985 18 222233crossref pubmed scopus 1051 google scholar 8paulesu e dmonet jf fazio f et aldyslexia cultural diversity biological unityscience 2001 291 21652167crossref pubmed scopus 836 google scholar 9bradley l bryant pe categorizing sounds learning reada causal connectionnature 1983 301 419421crossref scopus 2081 google scholar appropriate pedagogy may offer hope otherwise face lifetime avoiding reading writing consequence unfulfilled potential10torgesen jk morgan st davis c effects two types phonological awareness training word learning kindergarten childrenj educ psychol 1992 84 364370crossref scopus 204 google scholar recently educators fully appreciated nature reading disability part medical terminology distanced teachers narrow preconceptions diversity human academic aptitudes lack alternative scientifically verified remedial techniques also prevented educational systems providing effective intervention light current state knowledge denial appropriate educational service reading disability longer defensible society educational systems question incidence learning disorders crucial academic outcome learner optimized characteristics students require altered educational instruction specific alterations must instruction entail long delivered toward end katusic colleagues11katusic sk colligan rc barbaresi wj schaid dj jacobsen sj incidence reading disability populationbased birth cohort 19761982 rochester minnmayo clin proc 2001 76 10811092abstract full text full text pdf pubmed scopus 233 google scholar mounted mammoth effort public private sectors medical investigators educators pooled resources address questions well demographic issue biological implications gender representation reading disability work demonstrates powerfully impact definition determination incidence thus qualification service based common definitional criterion reading disability unrecognized education service providers one third study subjects consequence untreated although incidence ranges broad 53 118 even stringent exceeds cap 3 federal government put provision services learning disabilities initial stages implementation 1975 education handicapped children act12us office education assistance states education handicapped children procedures evaluating specific learning disabilitiesfed regist 1977 42 6208262085google scholar combined incidence mental retardation cerebral palsy epilepsy reach 3 us population yet considered important medical educational concerns katusic et al correctly point data overestimate incidence reading disability probably close quantifying actual occurrence minnesota study applied 4 definitional formulas including used connecticut longitudinal study13shaywitz se shaywitz ba fletcher jm escobar md prevalence reading disability boys girls results connecticut longitudinal studyjama 1990 264 9981002crossref pubmed scopus 694 google scholar14shaywitz se escobar md shaywitz ba fletcher jm makuch r evidence dyslexia may represent lower tail normal distribution reading abilityn engl j med 1992 326 145150crossref pubmed scopus 538 google scholar several features distinguish 2 important attempts epidemiological investigation reading disability study katusic et al comprised much larger sample includes entire birth cohort excluding migrating region dying correcting variable duration observation kaplanmeier projections connecticut sample size much smaller yet investigators selection subjects statistically defensible reasonable sampling method minnesota study although including great deal data every instance record iq measure apply instrument measure academic performance whereas connecticut study design consistent means data collected advantage prospective retrospective study design current report minnesota confined incidence gender distribution reading disability characteristics population yet evaluated cohort available analysis evidenced recent report attention deficit disorder group15leibson cl katusic sk barbaresi wj ransom j obrien pc use costs medical care children adolescents without attentiondeficithyperactivity disorderjama 2001 285 6066crossref pubmed scopus 315 google scholar connecticut study include multigrade inventory teachers means classroom behavioral observations students recorded allowing investigators conclude greater frequency behavioral manifestations boys reading disability strong factor referral school evaluation13shaywitz se shaywitz ba fletcher jm escobar md prevalence reading disability boys girls results connecticut longitudinal studyjama 1990 264 9981002crossref pubmed scopus 694 google scholar indeed clinical experience medicine well suggests behavioral concern much frequent reason referral assessment isolated failure achieve nonetheless minnesota cohort offers rich resource one anticipate analysis learning behavioral disturbances contribution connecticut studies investigation diminish reading disability occur girls13shaywitz se shaywitz ba fletcher jm escobar md prevalence reading disability boys girls results connecticut longitudinal studyjama 1990 264 9981002crossref pubmed scopus 694 google scholar girls well boys written language disorder may persist adulthood however none connecticut reports frequency girls equal exceed boys katusic et al addressed gender effect might overemphasized sample size interestingly colorado twin studies reading disability shown powerful effect gender suggest higher iq increases risk heritable reading disorder16defries jc knopik vs wadsworth sj colorado twin study reading disabilityin duane dd reading attention disorders neurobiological correlates york press baltimore md1999 1742google scholar raises possibility higher iq minnesota population boys may influenced slightly identification reading disability favor fact sex may influence probability reading failure biological observation raises interesting questions among possible mechanisms explain sex difference sex chromosomal influence obviously one sexlinked mendelian sense testosterone effects intrauterine brain development present male female fetuses17geschwind n reaction conference sex differences dyslexiain ansara geschwind n galaburda albert gartrell n sex differences dyslexia orton dyslexia society baltimore md1981 xiiixviiigoogle scholar sex differences brain function suggested yale studies bilateral brain phonological processing functional magnetic resonance imaging female subjects opposed unilateral function male subjects18shaywitz ba shaywitz se pugh kr et alsex differences functional organization brain languagenature 1995 373 607609crossref pubmed scopus 1097 google scholar although population connecticut longitudinal study ethnically racially heterogeneous minnesota birth cohort neither study addresses issue innercity underachievement social cultural linguistic factors complicate academic performance require separate investigation current estimates double frequency reading underachievement underprivileged populations need clarification whether instructional modifications effective populations connecticut rochester minn benefit harlem watts innercity chicago preliminary data indicate least reading performance may improved risk populations19blachman ba ball ew black rs tangel dm kindergarten teachers develop phoneme awareness lowincome innercity classrooms make differencereading writing 1994 6 118crossref scopus 124 google scholar studies suggested students low performance reading underperform arithmetic well20shaywitz ba fletcher jm holahan jm shaywitz se discrepancy compared low achievement definitions reading disability results connecticut longitudinal studyj learn disabil 1992 25 639648crossref pubmed scopus 167 google scholar done atrisk population enhance educational achievement important reading performance technologically oriented society recent observations suggest lowest probability employability among students poor calculation quantification skills21west tg minds eye visual thinkers gifted people dyslexia learning difficulties computer images ironies creativity updated ed prometheus books amherst ny1997google scholar whether poor prognosis based solely weak aptitude mathematics related concomitant features inattentiveness poor coordination social unawareness well reading disability awaits investigation results studies funded nichd prompt educational establishment reexamine differences human learning dyslexic subjects shown unusual skills engineering graphic performing arts athletics22siegel gaylordross r factors associated employment success among youths learning disabilitiesj learn disabil 1991 24 4047crossref pubmed scopus 19 google scholar thus possible student old 12 14 years might qualify advanced curriculum sciences yet require support written language helpful technological aids computer spell checks orally prompted computer writing systems may students needs determined possible none 4 criteria applied katusic et al define individuals many us known classmates colleagues brilliant aspect science mathematics spelling learning second language arduous implications minnesota connecticut studies public instruction profound one cannot anticipate services defined past special education applied upwards 10 school population rather general education must consider remedies include smaller classroom size teacher training proved effective strategies instruction reading monitoring reading writing performance throughout students educational lifespan apparently biological trait reading disability associated commonly later difficulties spelling learning second language23dinklage kt inability learn foreign languagein blaine jr gb mcarthur cc emotional problems student 2nd ed appletoncenturycrofts new york ny1971 185206google scholar question instability diagnosis way individuals reading disability changes expression time reflects limitation arbitrary formulas rather discontinuous trait14shaywitz se escobar md shaywitz ba fletcher jm makuch r evidence dyslexia may represent lower tail normal distribution reading abilityn engl j med 1992 326 145150crossref pubmed scopus 538 google scholar report academic medical center powerfully demonstrates utility interdisciplinary investigation matters education may help shape appropriate public policy incidence reading disability populationbased birth cohort 19761982 rochester minnmayo clinic proceedingsvol 76issue 11previewto report incidence reading disability among schoolaged children fulltext pdf