Different Types of Dyslexia

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David is not a dunce. In fact, according to the evaluations of several professionals he is rather intelligent. Yet he certainly has a problem, and shares his problem with millions of other children and adults.

David, according to these professionals, is dyslexic.

The term “dyslexia” was introduced in 1884 by the German ophthalmologist, R. Berlin. He coined it from the Greek words dys meaning ill or difficult and lexis meaning word, and used it to describe a specific disturbance of reading in the absence of pathological conditions in the visual organs. In a later publication, in 1887, Berlin stated that dyslexia, “presuming right handedness,” is caused by a left-sided cerebral lesion. He spoke of “word-blindness” and detailed his observations with six patients with brain lesions who had full command over verbal communications but had lost the ability to read.

In the century to follow the narrow definition Berlin attached to the term dyslexia would broaden. Today the term dyslexia is frequently used to refer to a “normal” child — or adult — who seems much brighter than what his reading and written work suggest. While the term is mostly used to describe a severe reading problem, there has been little agreement in the literature or in practice concerning the definition of severe or the specific distinguishing characteristics that differentiate dyslexia from other reading problems.

The terms phonological dyslexia and surface dyslexia are generally used to describe two main types of dyslexia.

Phonological dyslexia

This type of dyslexia includes trouble breaking words down into syllables and into smaller sound units called phonemes. For example, if you say a word out loud to a child with weak phonemic skills, she can hear the word just fine and repeat it back to you. But she’ll have trouble telling you how to split it apart into the different sounds that make up this word.

Difficulties in this area can make it hard for readers to match phonemes with their written symbols (graphemes). This makes it hard to sound out or “decode” words.

One way children get tested for issues in these areas is by being asked to read fake words, like jeet. The idea is to show kids a word they’ve never come across before and see if they can sound it out.

You may hear some people talk about dysphonetic dyslexia or auditory dyslexia. These are synonymns for phonological dyslexia.

You may also hear some people use the phrase double deficit. This refers to kids who struggle with phonological awareness and with something called rapid automatised naming. This term describes the ability to quickly name several things in a row, such as numbers or colours.

Some experts think slow naming speed reflects difficulties with phonological processing in reading. Others think it encompasses a different skill we use to read fluently. Overall processing speed may also play a role.

Corinne Roth Smith lists the reading and spelling patterns of children with phonological dyslexia:

  • Difficulty discriminating between individual sounds in beginning reading instructions (occurs very seldom).
  • Difficulty processing rapid auditory inputs so that consonant sounds that cannot be sustained (p-b) are not perceived; these may then be omitted in reading.
  • Poor ability to analyse the sequence of sounds and syllables in words; consequently they become reversed in reading words; this is akin to the problem faced orally when poor auditory analysis has taught the child such phrases as “lead a snot into temptation” and “Harold be Thy name” in the Lord’s prayer, or “lmnop” being one lumped cluster in the alphabet song.
  • Poor ability to remember individual sounds or sequences of sounds.
  • Difficulty blending individual sounds into words.
  • Difficulty listening to words and omitting one sound and substituting it for another (say cat; now take off the /c/ and put on an /f/); such abilities are essential for word analysis because that is what figuring out how to phonetically decode a word is all about; children usually develop this skill with initial consonants, and then medial vowels or consonants.
  • Difficulty remembering the sounds that individual letters and phonetically regular and irregular letter combinations represent.
  • Inability to rapidly retrieve letter sounds while analysing words, so that the beginning of the word is forgotten by the time the last letter of the word is recalled (naming problem).
  • Difficulty analysing unknown words because of poor knowledge of phonetic rules and difficulty sequencing sounds.
  • Difficulty applying the phonetic rules from words that can be read to pseudowords that follow the same pattern but are not real words.
  • Vowel sounds are particularly troublesome.
  • Word substitutions that are conceptually (person, human) or visually (horse, house) related, but not phonetically related.
  • Limited sight vocabulary because the student cannot memorise an abundance of words without the benefit of phonetic cues.
  • Guessing at unfamiliar words rather than employing word-analysis skills.
  • Spelling remains below reading level because it is attempted by sight rather than by ear.
  • Correct spellings occur primarily on words that the child has encountered repeatedly and therefore can revisualise.
  • Bizarre spellings that seldom can be identified, even by the child, because they do not follow phonetic patterns.
  • Extraneous letters and omitted syllables in spelling.

Surface dyslexia

Some kids struggle with reading because they can’t recognise words by sight. This is an important skill for a couple reasons. One is that some words have tricky spellings. Words like weight and debt can’t be sounded out — readers need to memorise them.

The other reason has to do with reading fluency. To be able to read quickly and accurately, kids need to recognise many common words at a glance—without sounding them out.

For example, beginning readers will come across a word like and many times. Eventually they’ll get so familiar with it that they don’t need to sound it out anymore. They can recognise it almost like a picture. But most children with dyslexia have problems sounding out words. This makes it hard to build a sight word vocabulary.

Some researchers have suggested that there’s a subtype of dyslexia that makes it hard to remember what words look like. This subtype is sometimes referred to as surface dyslexia. You may also hear it called dyseidetic dyslexia or visual dyslexia.

Author Corinne Roth Smith lists the reading and spelling patterns of children with surface dyslexia:

  • Confusion with letters that differ in orientation (b-d, p-q).
  • Confusion with words that can be dynamically reversed (was-saw).
  • Very limited sight vocabulary; few words are instantly recognised from their whole configuration — they need to be sounded out laboriously, as though being seen for the first time.
  • Losing the place because one doesn’t instantly recognise what had already been read, as when switching one’s gaze from the right side of one line to the left side of the next line.
  • Omitting letters and words because they weren’t visually noted.
  • Masking the image of one letter, by moving the eye too rapidly to the subsequent letter, may result in omission of the first letter.
  • Difficulty learning irregular words that can’t be sounded out (for example, sight).
  • Difficulty with rapid retrieval of words due to visual retrieval weaknesses.
  • Visual stimuli in reading prove so confusing that it is easier for the child to learn to read by first spelling the words orally and then putting them in print.
  • Insertions, omissions, and substitutions, if the meaning of the passage is guiding reading.
  • Strengths in left hemisphere language-processing, analytical and sequential abilities, and detail analysis; can laboriously sound out phonetically regular words even up to grade level.
  • Difficulty recalling the shape of a letter when writing.
  • Spells phonetically but not bizarrely (laf-laugh; bisnis-business).
  • Can spell difficult phonetic words but not simple irregular words.

Edublox programmes are effective in overcoming dyslexia and other learning difficulties by addressing the underlying shortcomings that interfere with academic performance.

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