ABSTRACT
Duringthepastfourdecades,dyslexiaresearchhasbeendominatedbythephonologicaldeˆcithypothesis.Accordingtothisview,thecausesofword-level reading impairments can be traced to deˆcits in language-based processes that arespecializedfortheprocessingofspeech(Vellutino,Fletcher,Snowling,& Scanlon,2004).Thetheoreticalbackdropforthismodel,andindeedmuchof theevidence,canbeattributedtothein—uentialworkofShankweilerandhis colleagues.Fromhisearliestwritings(e.g.,Shankweiler,1964),Shankweiler rejected the view that poor reading might be a consequence of a visual perceptualabnormality.Instead,recognizingtheimportanceofphonemesegmentation andcodingprocessestotypicalreadingdevelopment(Liberman&Shankweiler, 1991),hearguedthat,therein,istheproblemofdyslexia.Inshort,dyslexiacanbe consideredaphonologicalcodingdeˆcitthatcompromisestheacquisitionofthe alphabetic principle (Byrne, 1998); in turn, this has downstream effects on decodingprocessesinreading,spelling,andtosomeextentgrammaticalprocessing (Shankweiler&Crain,1986).WhereasinEnglishtheprimaryfeatureofdyslexia isadifˆcultywithreadingandspellingaccuracy,intransparentorthographies, theprimarymanifestationisadeˆcitinreading—uency,butinallcasesphonological skills are impaired (Caravolas 2005, for a review). Within this model, the phonologicaldeˆcitisnecessaryandsufˆcienttocausethereadingimpairment in dyslexia (Morton & Frith, 1995).
