Development of dyslexic subgroups: A one-year follow up

There is a consensus that dyslexia is on a continuum with normal reading sk ill and that dyslexics fall at the low end of the normal range in phonologi cal skills. However, there is still substantial variability in phonological skill among dyslexic children. Recent studies have focused on the high end of the continuum of phonological skills in dyslexics, identifying a "surfa ce" dyslexic, or "delayed" profile in which phonological skills are not out of line with other aspects of word recognition. The present study extended this work to a longitudinal context, and explored differences among subgro ups of dyslexics on a battery of component reading skills. Third grade dysl exics (n = 72) were classified-into two subgroups, phonological dyslexics a nd delayed dyslexics, based our comparisons to younger normal readers at th e same reading level (XL group). The children were tested at two points (in third and fourth grade). The results revealed that the classification of d yslexics produced reliable, stable, and valid groups. About 82 percent of t he children remained in the same subgroup category when retested a year lat er. Phonological dyslexics were lower in phoneme awareness and expressive l anguage. Delayed dyslexics tended to be slower at processing printed letter s and words but not at rapid automatic naming of letters, and relied more h eavily on phonological recoding in reading for meaning than did phonologica l dyslexics, A subset of the delayed dyslexics with the traditional "surfac e dyslexic" pattern (relatively high pseudoword and low exception word read ing) wits also identified. The surface subgroup resembled the XL group on m ost measures and was not very stable over one year The results are discusse d in light of current models of dyslexia and recent subgrouping schemes, in cluding the Double-Deficit Hypothesis.