Different kinds of dyslexia would require different kinds of interventions. This suggests it is important we identify any varieties that might exist. As a first step, consider the diagram above that classifies reading disabilities into three groups. About 20% of people have a reading disability and they fall somewhere in the three blue circles depending on their deficits.
Difficulty decoding or assembling words based on their sounds.
Slow reading; poor use of sight words. A sight word is a word that is instantly recognized by the reader; is not sounded out, and requires almost no effort to understand.
Poor understanding of what was just read.
But people with severe reading disabilities aren’t randomly distributed across the three deficit circles. A whopping 80% have a phonological deficit and fall in the top bubble. These are the ones we would call dyslexic. They have difficulty discriminating and manipulating phonemes, lacking the ability to easily decode or assemble words based on their constituent sounds.
About 20% of those with reading disabilities have speed and/or comprehension problems but can sound out words without difficulty – they technically don’t have dyslexia but will need reading help, just a different kind of help. See the Dyslexia Treatment page for more details on the specific kinds of help.
All varieties of dyslexia involve a significant phonological deficit, regardless of whether there is a comprehension or speed deficit. In practice, most dyslexics have at least two deficits.
Can we divide the group of people who are in the top bubble further into more specific dyslexia types? Are there 101 flavours? The short answer is yes, there are different types and these types do have some implications for treatment.
Unfortunately, academics and researchers identify and define more types of dyslexia than parents and teachers can keep track of. Further, many websites define different types incorrectly or discuss types which are not widely recognized at all.
Below is a taxonomy of only the most commonly recognized and discussed types of dyslexia.