What Are Reading Disabilities?
Researchers have identified three kinds of developmental reading disabilities that often overlap but that can be separate and distinct:
- Phonological deficit, implicating a core problem in the phonological processing system of oral language.
- Processing speed/orthographic processing deficit, affecting speed and accuracy of printed word recognition (also called naming speed problem or fluency problem).
- Comprehension deficit, often coinciding with the first two types of problems, but specifically found in children with social-linguistic disabilities (e.g., autism spectrum), vocabulary weaknesses, generalized language learning disorders, and learning difficulties that affect abstract reasoning and logical thinking.
For purposes of research, “reading disabled” children may be all those who score below the 30th percentile in basic reading skills. Among all of those poor readers, about 70-80 percent have trouble with accurate and fluent word recognition that originates with weaknesses in phonological processing, often in combination with fluency and comprehension problems. These students have obvious trouble learning sound-symbol correspondence, sounding out words, and spelling. The term dyslexic is most often applied to this group.
Another 10-15 percent of poor readers appear to be accurate but too slow in word recognition and text reading. They have specific weaknesses with speed of word recognition and automatic recall of word spellings, although they do relatively well on tests of phoneme awareness and other phonological skills. They have trouble developing automatic recognition of words by sight and tend to spell phonetically but not accurately. This processing speed/orthographic subgroup generally has milder difficulties with reading than students with phonological processing deficits.
Yet another 10-15 percent of poor readers appear to decode words better than they can comprehend the meanings of passages. These poor readers are distinguished from dyslexic poor readers because they can read words accurately and quickly and they can spell. Their problems are caused by disorders of social reasoning, abstract verbal reasoning, or language comprehension.