Subtypes of reading disability in a shallow orthography: a double dissociation between accuracy-disabled and rate-disabled readers of Hebrew.
Whereas most English language sub-typing schemes for dyslexia (e.g., Castles & Coltheart, 1993) have focused on reading accuracy for words varying in regularity, such an approach may have limited utility for reading disability sub-typing beyond English in which fluency rather than accuracy is the key discriminator of developmental and individual differences in reading ability. The present study investigated the viability of an accuracy/fluency-based typology in a regular orthography, pointed Hebrew. We sought evidence of true or "hard" accuracy/rate subtypes in the strict (double dissociation) sense of selective impairment on only one dimension in the presence of normal levels of performance on the other dimension. In a nationally representative sample of fourth graders, we were able to identify a specific accuracy-disabled sub-group as well as an equally specific rate-disabled subgroup. Validating this subdivision, we show that the nature of reading performance in these subgroups and their converging cognitive/linguistic profiles are unique and distinctive on variables other than the measures used to define them. While the rate-specific disability appeared to reflect a general deficit in speed of processing affecting reading rate, and rapid automatized naming of print-related material, the accuracy-only disability subgroup displayed selective deficits in phonological awareness and morphological knowledge. Biosocial, demographic, and instructional factors, furthermore, did not explain the sub-group differences. It appears that both these subtypes are equally prevalent each counting close to 10% of the population.
Department of Learning Disabilities, Edmond J. Safra Brain Research Center in Learning Disabilities, The University of Haifa, Mt. Carmel, Haifa, 31905, Israel.. shany.michal7@gmail.com
Michal
M
Shany
David L
DL
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D002648:Child; D004410:Dyslexia / Q000145:classification* / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007557:Israel; D007802:Language; D007807:Language Tests / Q000592:standards / Q000706:statistics & numerical data; D008297:Male; D008570:Memory, Short-Term; D010700:Phonetics; D011897:Random Allocation; D011932:Reading; D015203:Reproducibility of Results; D012720:Severity of Illness Index