- Distinguished by semantic reading errors, for example reading the word ‘heart’ as ‘blood’ or ‘street’ as ‘road’
- Also characterized by visual errors such as reading ‘house’ for ‘horse or derivational errors reading ‘sleep’ as ‘sleeping’
- Difficulty reading nonsense words
- Usually an acquired form of dyslexia resulting from stroke or brain injury (left hemisphere of the brain) but can be developmental
- A “dyseidetic” type of dyslexia meaning greater difficulty recognizing whole words rather than sounds (dysphonetic)
Deep dyslexia is an acquired form of dyslexia, meaning it arrives later in life and does not usually result from genetic, hereditary (developmental) causes.
It represents a loss of existing capacity to read, often because of head trauma or stroke that affects the left side of the brain. It is distinguished by two things:
1) Frequent semantic errors
A semantic error occurs when one word appears on the page, but an entirely different, but related word, is read. ‘Table’ may be read for ‘chair’, ‘street’ for ‘road’ or ‘dog’ for ‘canine’.
Semantic errors are strange creatures, almost appearing as complete guesses at words based on context clues or word shape and size. They result in part from extremely poor ability to sound out words and an over reliance on sight words.
2) Extreme difficulty reading nonsense words
Nonsense words are made up words that don’t exist like ‘bluck’ or ‘zub’. Strong readers will be able to quickly decode/sound out these words, but deep dyslexics have extreme difficulty doing this or simply cannot do it at all.
It has been proposed (Glosser and Friedman (1990)) that deep and phonological dyslexia may be opposite endpoints on a continuum of reading disability. Surface dyslexia would fall in between.
Implications for Treatment
Deep dyslexics have trouble with both sounding out words and recognizing whole words, providing for two kinds of interventions. Research has shown that treatment for either approach in isolation or both approaches together can improve reading ability.
Treatment to improve the sounding out of words (phonological/non lexical):
- Teaching explicit rules for sounding out words
- Teaching explicit rules for spelling
Techniques for improving the ability to identify whole words (Lexical)
- Sentence completion
- Repeated reading and copying of individual words and then using them in complete written sentences
In addition encourage careful processing of each word by allowing a lot of time for reading of even short pieces of text.
Final thoughts on deep dyslexia
Deep dyslexia is a relatively exotic form of dyslexia, not common among young children. Typically it is acquired later in life after a stroke or some kind of head trauma.
The kinds of errors typically made should not be confused with the odd guesses that younger dyslexic children may make when unable to identify or sound out a word. In those cases, they may choose a word that is similar in shape or size, or guess based on context clues, but they will usually not make odd semantic errors such as reading ‘dog’ for ‘canine’.