Dyslexia and dysgraphia in Greek in relation to normal development : cross-linguistic and longitudinal studies
Studies on developmental dyslexia in transparent orthographies have established that children learning to read in such languages hardly experience difficulties in word reading accuracy and phonological awareness tasks, but suffer from a reading speed deficit. On the other hand in the English orthography, where the mappings between graphemes and phonemes are largely inconsistent, children exhibit significant difficulties in both word reading accuracy and speed. Greek is characterized by a high degree of regularity for reading, but is inconsistent for spelling. The variability of phoneme-to-grapheme correspondences and the highly inflectional nature of the particular orthography constitute spelling in Greek a considerably demanding task. The present thesis comprises three studies that were concerned with understanding the reading and spelling difficulties that Greek children/participants with dyslexia have and their underlying cognitive deficits, in relation to typically developing children and English children/participants with dyslexia. The first study examined the reading and spelling difficulties in Greek- and English-speaking children/participants with dyslexia, each compared with two control groups. Greek children/participants with dyslexia outperformed their English counterparts on word/nonword phoneme deletion, word/nonword reading, and grammatical spelling. However the two language groups performed similarly on rapid digit naming, spoonerisms and on the choice tasks. Results are discussed in relation to the differences in orthographic consistency between the two languages. The second study examined the development of literacy skills in twenty-three Greek children/participants with dyslexia over a period of 18 months (10 years 5 months to 12 years 3 months). At Time 1 children/participants with dyslexia performed worse on literacy tests than chronological-age control children, but similarly to reading-age controls. At Time 2 children/participants with dyslexia performed worse on all the tasks than CA control children, and worse than RA controls on the tasks of phoneme deletion of nonwords, nonword reading and orthographic spelling. Moreover the concurrent and longitudinal predictors of children's/participants' with dyslexia and typically developing children's reading and spelling abilities were examined. The findings are discussed in relation to theories of normal and atypical reading and spelling development. The third study investigated the ability of twenty-three 10-13 year-old Greek children/participants with dyslexia, and their reading-level and age-level-matched children to spell derivational and inflectional suffixes. Children/participants with dyslexia performed significantly worse than CA controls and RA controls. When they spelled the inflectional ending of adjectives and nouns children/participants with dyslexia did not differ from RA controls. It is suggested that children/participants with dyslexia have weaknesses in grasping the morphological rules of the Greek orthographic system and applying this knowledge in the spelling of word suffixes. The thesis concludes with a discussion of findings in relation to previous literature, the limitations of the present studies and avenues for future research.