Deep dyslexia is a very rare subtype of acquired dyslexia. The hallmark feature of this condition is the frequent semantic substitution of words while reading, says Alan M. Hultquist in his book, An Introduction to Dyslexia for Parents and Professionals.
Individuals with deep may replace words with others that are related in meaning, even though they do not look or sound similar. For example, someone might read merry as Christmas, or ice cream as cone. These are called coordinate errors (e.g., tulip for rose, comb for brush, mother for cousin).
Key features of deep dyslexia include:
- Difficulty reading function words (e.g., reading at as in, or through as after).
- Better ability to read concrete nouns (words that can be visualized like car, hammer) than abstract or functional words.
- Profound challenges with decoding (sounding out words), including an inability to read nonwords (e.g., mab).
- Trouble identifying letter sounds when shown a letter, but potentially better at writing the letter when the sound or name is given.
Two case studies are described:
- KJ, a 13-year-old girl, made consistent semantic errors and couldn’t sound out nonwords. She had a reversed ability to associate sounds with letters—able to choose the correct letter when hearing a sound, but not vice versa.
- A group of younger children (7–8 years old) studied by Linda Siegel showed similar traits: poor decoding of nonwords and semantic substitutions when reading.
Hultquist emphasizes that such errors must occur when reading word lists—not just in connected text—because ordinary poor or novice readers also guess words using context, which can appear similar but is not the same phenomenon.
The author concludes by reinforcing how exceptionally rare deep dyslexia is. Despite 30 years in teaching and evaluation, he notes he has never personally encountered a true case.
