Dyslexia is a language-based learning disability. Dyslexia refers to a cluster of symptoms, which result in people having difficulties with specific language skills, particularly reading. Students with dyslexia usually experience difficulties with other language skills such as spelling, writing, and pronouncing words. Dyslexia affects individuals throughout their lives; however, its impact can change at different stages in a person’s life. It is referred to as a learning disability because dyslexia can make it very difficult for a student to succeed academically in the typical instructional environment, and in its more severe forms, will qualify a student for special education, special accommodations, or extra support services.


Types of dyslexia


Dyslexia types based on causes

1. Primary dyslexia

Clinicians have known for a long time that dyslexia runs in families, which means a child with a parent with dyslexia is likelier to have the learning difficulty themselves. Primary dyslexia refers to dyslexia when it is the result of a genetically inherited condition.

2. Secondary dyslexia

Secondary dyslexia refers to reading difficulties caused by problems with brain development during the early stages of fetal development. Note that both primary and secondary dyslexia are considered developmental.

3. Developmental dyslexia

The term developmental dyslexia refers to an unexpected difficulty in reading in children and adults who otherwise possess the intelligence, motivation, and schooling considered necessary for accurate and fluent reading. Developmental dyslexia distinguishes the problem in children and youth from similar issues experienced by persons after severe head injuries.

4. Acquired dyslexia

When an adult or child has a brain injury from trauma or disease, they can sometimes develop difficulties with language processing, which may result in dyslexia. This type of dyslexia is referred to as acquired or trauma dyslexia.

Dyslexia types based on symptoms

The terms phonological dyslexia and surface dyslexia are generally used to describe two main types of dyslexia. Synonyms for phonological dyslexia aredysphonetic dyslexia and auditory dyslexia, and synonyms for surface dyslexia are dyseidetic dyslexia, visual dyslexia, and orthographic dyslexiaDeep dyslexia is sometimes used to describe a severe impairment.

5. Phonological dyslexia

This type of dyslexia includes trouble breaking words into syllables and smaller sound units called phonemes. For example, if you say a word out loud to a child with weak phonemic skills, he can hear the word just fine and repeat it back to you. But he’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 challenging for readers to match phonemes with their written symbols (graphemes), which makes it hard to sound out or “decode” words.

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

Smith (1991) lists other reading and spelling patterns of children with phonological dyslexia:

6. Surface dyslexia

This type of dyslexia refers to kids who struggle with reading because they can’t recognize words by sight. Sight-reading is an essential skill for a couple of reasons. One is that some words have tricky spellings. For example, words like weight and debt can’t be sounded out — readers need to memorize them. The other reason has to do with reading fluency. To read quickly and accurately, kids need to recognize many common words at a glance — without sounding them out.

Smith (1991) lists other reading and spelling patterns of children with surface dyslexia:

7. Deep dyslexia

Deep dyslexia is used to describe a severe impairment. It is accompanied by semantic errors (e.g., street is read as road), but also visual errors (e.g., badge is read as bandage), derivational errors (e.g., edition is read as editor), and difficulty reading functional words (e.g., astheso). Deep dyslexia is often described as an acquired reading disorder due to a brain injury (Mather & Wendling, 2012).

More dyslexia types,

8. Letter position dyslexia

Individuals with a deficit in this function can identify the letters correctly but fail to encode the order of the letters within the word. This dyslexia type is called letter position dyslexia (LPD), and its cardinal symptom is the migrations of letters within words. Thus, words like cloud can be read as couldfried as fired, and dairy as diary. Another related error that individuals with LPD make is the omission of doubled letters: for example, they may read drivers as divers, and baby as bay.

9. Attentional dyslexia

In attentional dyslexia, letters migrate between neighboring words, but are correctly identified and keep their original relative position within the word. For example, the word pair cane love can be read as lane love or even lane cove.

10. Letter identity dyslexia

Letter identity dyslexia is a deficit in the orthographic-visual analysis, in the function responsible for creating abstract letter identities. It is not a visual deficit, as readers with this dyslexia can still match similar non-orthographic forms, visually match two instances of the same letter in different sizes, and copy letters correctly. However, readers with LID cannot access the abstract identity of letters from their visual form, so they cannot name a letter, identify a written letter according to its name or sound, or match letters in different cases (e.g., A and a) or fonts.

11. Neglect dyslexia

A condition in which a person is unaware of half of the visual field due to neurological damage. Either the initial parts of words are misread (left neglect) or the terminal parts of words are misread (right neglect). These errors are not simple deletions but typically guesses of actual though incorrect words with approximately the correct number of letters. The person with neglect dyslexia may read blend as lend and shown as show.

12. Vowel letter dyslexia

Individuals with vowel dyslexia omit, substitute, transpose, and add vowel letters. Thus, the word bit can be read as batbut, or even boat.

Some scholars say that research does not support using dyslexia subtypes to guide assessment and intervention (Peterson et al., 2014).

Double deficit 

You may also hear some people use the phrase, double deficit. Double deficit refers to kids who struggle with phonological awareness and with something called rapid automatized naming (RAN). Rapid naming refers to the speed with which one can retrieve the names of symbols (letters, numbers, colors, or pictured objects) from long-term memory. People with dyslexia usually score poorer on RAN assessments than typical readers. 


Sign and symptoms of dyslexia

The problems displayed by individuals with dyslexia involve difficulties in acquiring and using written language. It is a myth that individuals with dyslexia “read backwards,” although spelling can look quite jumbled at times because students have trouble remembering letter symbols for sounds and forming memories for words. Other problems experienced by people with dyslexia include the following:

·       Learning to speak

·       Learning letters and their sounds

·       Organizing written and spoken language

·       Memorizing number facts

·       Reading quickly enough to comprehend

·       Persisting with and comprehending longer reading assignments

·       Spelling

·       Learning a foreign language

·       Correctly doing math operations

Not all students who have difficulties with these skills have dyslexia. Formal testing of reading, language, and writing skills is the only way to confirm a diagnosis of suspected dyslexia.

Causes of dyslexia

The exact causes of dyslexia are still not completely clear, but anatomical and brain imagery studies show differences in the way the brain of a person with dyslexia develops and functions. Moreover, most people with dyslexia have been found to have problems with identifying the separate speech sounds within a word and/or learning how letters represent those sounds, a key factor in their reading difficulties. Dyslexia is not due to either lack of intelligence or desire to learn; with appropriate teaching methods, students with dyslexia can learn successfully.