One of my favorite radio programs is the excellent Science Friday, which is broadcast on NPR (National Public Radio) in the USA. A recent edition talked about the plasticity of the human brain and included some interesting statements about research into treatments for dyslexia. I had not heard of the studies linking dyslexia to hearing difficulties - not vision processing difficulties as one might assume. You can find an MP3 download at the link above.
Clarification: I should have said "linking dyslexia to auditory processing difficulties" or something similar, not "hearing difficulties", which was too ambiguous. I should have also said "not only vision processing difficulties", as some theories of the roots of dyslexia still focus on vision processing (for instance, the so called magnocellular theory).
The root causes of dyslexia are not fully understood and serious research is ongoing. I suggest the following Nature article (Franck Ramus, 2001) for an overview.
I would also like to say "thank you" to the readers who pointed out my misstatement and the ensuing discussions in the comments. If you are just now coming across this post, I recommend reading the comments to catch up.
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3 comments:
Hi, it is Liz from I Speak of Dreams.
I think you misunderstood. It isn't a hearing problem, it's a processing or response problem.
Eide Neurolearning Blog
"dyslexic subjects showed delayed responses to sounds (HP stands for Huggins Pitch, TN stands for pure tone)when played with background noise."
Dyslexia is rarely a vision issue, either (although I am aware that point of view is more popular in the UK than in the US)
Dyslexia
Current research indicates that the vast majority of children with dyslexia have phonological core deficits. The severity of the phonological deficits varies across individuals, and children with these deficits have been shown to make significantly less progress in basic word reading skills compared to children with equivalent IQs. For example, some experts report that between ages 9 and 19, children with dyslexia who have phonological deficits improve slightly more than one grade level in reading, while other children with learning disabilities (LD) in the same classroom improve about six grade levels. Without direct instruction in phonemic awareness and sound-symbol correspondences, these children generally fail to attain adequate reading levels.
Definition
Phonological core deficits entail difficulty making use of phonological information when processing written and oral language. The major components of phonological deficits involve phonemic awareness, sound-symbol relations, and storage and retrieval of phonological information in memory. Problems with phonemic awareness are most prevalent and can coexist with difficulties in storage and retrieval among children with dyslexia who have phonological deficits.
Phonemic awareness refers to one's understanding of and access to the sound structure of language. For example, children with dyslexia have difficulty segmenting words into individual syllables or phonemes and have trouble blending speech sounds into words.
Storage of phonological information during reading involves creating a sound-based representation of written words in working memory. Deficits in the storage of phonological information result in faulty representations in memory that lead to inaccurate applications of sound rules during reading tasks.
Retrieval of phonological information from long-term memory refers to how the child remembers pronunciations of letters, word segments, or entire words. Children with dyslexia may have difficulty in this area, which leads to slow and inaccurate recall of phonological codes from memory.
Everyone who has commented is generally right that the majority of dyslexics have phonological problems. Their problems with language are often evident even before the age when he or she starts to read.
A minority of dyslexics have predominantly visual problems and most of these dyslexics surprise their parents and teachers with their difficulty learning to read because they have normal verbal development. When these visual dyslexics,a minority of dyslexics, describe symptoms such as not being able to read because the letters are moving around to much or there is an amount of time before the next word comes into focus, it is easy to see their problem isn't phonological.
I sell See Right Dyslexia Glasses and focus on the group of dyslexics that can describe a visual problem that makes reading difficult. The dyslexia glasses have a success rate of 100% with this group. For more information about the glasses go to www.dyslexiaglasses.com .
Dear Liz and hayesatlbch,
thanks to you both. I have clarified my earlier post to take your comments into account. Another person suggested that I research magnocellular causes as a way to learn more about the pathologies associated with dyslexia, which led me to the Ramus article that I linked to in the clarification. If you are aware of other studies that I should investigate, I would be interested to know. Once again, thanks.
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