Definitions:

Define dyslexia

Dyslexia Types - the different types of dyslexia

How do you define dyslexia?

So how do you define dyslexia? What is it and what does it mean?

The term "dyslexia" is a bit difficult to define because it is used in so many different ways. To start with there are two different major schools of thought involved, each with its own range of applications.

First: In the literal, pure academic sense, the meaning of the word "dyslexia" comes from the roots, the origin, the etymology, if you will, of the word itself.

The word is formed from a combination of 'dys', referring to a state of not-working or problematic (as it means in 'dysfunctional', for example) and 'lexia' which refers to letters and words.

In this sense, users define the words 'dyslexia' and 'dyslexic' as terms that apply to anyone who might have difficulties or problems with reading written text.

Second: Parents of dyslexic children and dyslexic adults define dyslexia, and use the term, with a much wider range of use and application.

In this wider sense, the word dyslexia is applied to a range of symptomatic problems which include problems with reading, writing, spelling, translating among those three, and with numerous co-factors.

The co-factors and related conditions may include hearing difficulties, poor short-term memory and/or a lack of physical coordination.

They may also include a lack of a sense of direction (right-left; up-down), lack of time awareness (scheduling, performing tasks in proper order, physically getting themselves to the right place at the right time) and/or other co-present disabilities.

To define dyslexia in this wider, application sense, a good working definition could be:

Dyslexia is a specific learning disability, neurological in origin, that is characterized by difficulties with accurate or fluent word recognition and by poor spelling and decoding abilities.

For expansion and clarification one might add:

Dyslexic disabilities typically stem from a deficiency in the phonological component of language that is frequently unexpected in relation to other cognitive abilities and exposure to normal classroom instruction.

Secondary effects may include difficulties in reading comprehension and reduced reading activity which may slow down and impede progress in development of vocabulary and general knowledge.

O.K. So now we have a working definition of what 'dyslexia' means. Now what about the different types of dyslexia?

Dyslexia types -- Defining the different types of dyslexia

The first attempt to sub-divide dyslexia into different types was made in 1973. Marshall and Newcombe put forth the ideas of 'surface', 'phonological' and 'double-deficit' dyslexia.

The symptoms of Surface Dyslexia relate to the mistakes made where the rules of English pronunciation are inconsistent. For example, "bowl" is read as though it rhymed with "howl", and "pretty" might be read as though it rhymed with "jetty".

Phonological Dyslexia is a failure to grasp the phonic nature of the English language. Individuals with it have great problems reading new or nonsense words because they do not and cannot grasp the links between the individual sounds or phonemes and letters on the page.

Double-Deficit Dyslexia is the term applied to the condition of individuals who have both Surface Dyslexia and Phonological Dyslexia.

Auditory Dyslexia and Visual Dyslexia both stem from the magnocellular theory of dyslexia. This theory holds that dyslexics have neurological weaknesses in the magnocellular cells of the thalamus area of the brain. This area is where rapid processing of visual and auditory information takes place.

Many studies have shown that dyslexics do have weaknesses in their visual and auditory processing, but not to the same degree. A result can be that a child with poor hearing skills but with average visual skills may be diagnosed as having Auditory Dyslexia, whereas one with poor visual skills but average hearing may be diagnosed as having Visual Dyslexia.

Then there is Orthographic Dyslexia. Orthography is the set of symbols or letters that make up a language. In English this is the 26 letters of the alphabet whilst in Japanese or Chinese it covers thousands of different symbols. And so Orthographic Dyslexia relates to problems in identifying and manipulating letters in reading, writing and spelling.

The terms "dysphonetic" and "dyseidetic", have been used recently to describe two different dyslexia types. Each describes a different symptom group of these two different types of dyslexia.

The term dysphonetic applies to people who have difficulties in connecting sound to symbols. For example, they might have problems sounding out words, and mistakes in their spelling would reveal a very poor grasp of phonics in their command of their language.

Dysphonetic dyslexia is sometimes called "auditory" dyslexia, because it relates to how a person hears and mentally processes the sounds of their language(s).

In contrast, the term dyseiditic applies to people who, although they have a good, workable grasp of phonetic concepts, nevertheless have considerable difficulty with whole word recognition and with spelling.

Most commonly, words are spelled in such a way that, although you can easily sort them out phonetically, they are still very far from being correctly presented. For example, the word telephone might be spelled "telafone". There may also be transpositions or even complete reversals in spelling.

Examples could be the word "seen" being spelled as "nees" or "been" being spelled as "neeb". Different, incorrect, but the letters corresponding to the right sounds are all there, just in an incorrect order.

Dyseidetic dyslexia is sometimes called "surface dyslexia" or "visual dyslexia" because it relates to how a person sees and mentally processes the symbols, letters and word concepts of their language into correct written formats.