Researchers currently suggest that there are 3 kinds of developmental reading disabilities. They can often overlap but they 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.
If a child has a prominent and specific weakness in either phonological or rapid print (naming-speed) processing, they are said to have a single deficit in word recognition. If they have a combination of phonological and naming-speed deficits, they are said to have a double deficit. Double-deficit children are more common than single-deficit and are also the most challenging to remediate. Related and coexisting problems in children with reading disabilities often include:
faulty pencil grip and letter formation;
weak impulse control;
problems with comprehension of spoken language; and
confusion of mathematical signs and computation processes.
About 30 percent of all children with dyslexia also have attention deficit hyperactivity disorder (ADHD).
Essential components of reading instruction are
fluency including oral reading and
Difficulties can occur in the production, comprehension, and awareness within any language component at the sound, syllable, word, sentence, and discourse levels.
Phonemic Awareness The ability to identify phonemes as the units comprising syllables and words, and usually appears in children at age 6 or 7. Phonemic awareness is the acknowledgement that spoken words contain smaller sound elements (the units compromising syllables and words). It requires a child's ability to separate a word from its meaning. Children who are learning to read must be able to understand that written words are composed of graphemes, which is necessary in learning to decode. Difficulties in decoding can impair word recognition, which in turn influences reading fluency and comprehension. Phonemic awareness requires both cognitive and language skills. Rhyme, alliteration, and syllable awareness can be viewed as developmental early indicators of phonological awareness.
Phonics A student's ability to internalize and automate alphabetical symbols as representative of phonemes. (Sound-symbol correspondence) Phonics improves word recognition, spelling and reading comprehension. Phonological skills are the fundamentals for decoding. Children with dyslexia have difficulty with sound-symbol correspondence
Vocabulary Development Limited vocabulary causes difficulty in reading comprehension. Vocabulary development refers to a process by which you learn new words and increase your lexicon. When learning to read unfamiliar and new words, a child may not be able to orally identify words on a page because they are having word finding difficulties due to limited lexicon.
Fluency Fluency is the ability to decode a text accurately, quickly, and with proper expression. To group words into appropriate phrase units and produce these units with correct intonation, stress, and pausing. Seeing phrases as chunks of text rather than individual letters, will allow them to read more quickly. Fluency relies on proficient word recognition and comprehension. Word recognition includes knowledge of phonemic awareness, phonics, sound letter correspondence, and sight word reading.
Comprehension Comprehension is being able to understand the literal meaning of words and sentences. This also includes inspectional reading/systematic skimming where you obtain as much information as possible within a limited amount of time; analytic reading which is being able to thinking about the reading; and comparative reading, generating a critical interpret ion of the text. Comprehension involves all aspects of language.