January 15, 2007

What causes "dyslexia"

Good article in the Telegraph 0n Dyslexia:

Scientists have long asked why some otherwise normal children have difficulty in learning to read, but 650 research studies, which have converged on an intriguing and unexpected answer, have all but solved the puzzle. Most children who find learning to read difficult cannot distinguish the smallest sounds in words. They can hear these sounds but not separate them, which makes it difficult to link them to the letters by which they are represented. The ability to do this – which develops at about the age of five – is called phonological awareness. We are born with varying potential to develop this skill, which has nothing to do with intelligence.

The poorer the skill children inherit, the greater the problem in processing speech sounds and remembering them. Scientists recently discovered that our genes only start the story. What happens after birth is critical; it can cancel out a problem or make it worse: furthermore, it can cause the same neurological weaknesses that other children have inherited. Good parenting and good schooling will, therefore, reduce reading problems.


I'm not so sure that phonological awareness has "nothing to do with intelligence." Lack of PA skills correlates highly with low IQ. In any event, PA skills can be taught, but they are unfortunately not often taught well in most schools.

8 comments:

allen said...

That's 65 research studies and I'd use them all to keep warm.

The notion that popular dyslexia is the result of a hearing defect ought to lend itself easily to disproof.

If the source of dyslexia is a hearing defect then it should show up in situations unrelated to reading.

Do dyslexic kids display an analogous difficulty with the spoken word? There ought to some discernible deficit in the comprehension of the spoken word that parallels the lack of comprehension of the written word.

Going the other way, a measurable hearing deficit ought to correlated strongly with dyslexia. And since it's possible to diagnose hearing problems in very young children, it should be possible to predict which kids display dyslexia when they get old enough to start reading.

To get back to the research, that suspiciously high number sounds like meta-research to me and I've got serious doubts about mixing what was never intended to mix.

John said...

Who exactly picked the 650 studies and evaluated them to come up with the conclusions?

I don't really believe that there are that many quality studies to evaluate. I don't think I have seen a dozen double blind placebo controlled studies about dyslexia and no 2 were about the same subject.

Even the simplest type of study that should show evidence of the cause of dyslexia has never been done.

How about an evaluation of people who have become deaf or blind by accident before age 4 being tested and evaluated for dyslexia.

There would be no reason for their rate of dyslexia to be any different from the general population. If dyslexia is a hearing problem then deaf people shouldn't be dyslexic.

If dyslexia is a visual problem then blind people shouldn't be dyslexic.

This is a much more general truth about the cause of dyslexia.

Almost all studies that have investigated the cause of dyslexia have concluded that the factor under investigation is a factor for dyslexia. They also usually conclude that it is true for all dyslexics.

It is also true that most studies claim that the latest study is right and all previous studies are wrong.

I will start believing that there is a single cause for dyslexia when there is a single successful intervention. Until that time, I will consider dyslexia to be caused by a number of factors whose importance varies for each individual who is dyslexic.

Anonymous said...

Liz Ditz from I Speak of Dreams.

Allan said,

Do dyslexic kids display an analogous difficulty with the spoken word? There ought to some discernible deficit in the comprehension of the spoken word that parallels the lack of comprehension of the written word.

Yes and maybe.

Yes: One very early clue is a consistent mispronunciation of common polysyllabic words -- pisghetti or pisgedy for spaghetti, mazageen for mazagine, and so on.

Yes: Another early clue is an inability to generate rhymes. For example, a child who can recite rhymed couplets, but cannot generate ones independently.

Maybe: some kids who are later identified as dyslexic may also have difficulties with aural comprehension, Central Auditory Processing Disorder (CAPD). It's difficult to diagnose in very young children.


Going the other way, a measurable hearing deficit ought to correlated strongly with dyslexia. And since it's possible to diagnose hearing problems in very young children, it should be possible to predict which kids display dyslexia when they get old enough to start reading.

Don't mistake a difficulty in processing language sounds with a hearing deficit.

But certainly in the process of ruling out contributing causes, a child who is having difficulty learning to read should have a comprehensive vision examination and a comprehensive hearing examination.

I agree with KdeRosa that PA skills can be taught, but they are unfortunately not often taught well in most schools..

In general, Mills was writing about the state of dyslexia remediation and accomodation in the UK, which is not identical to that in the US. As poor as it can be in the US, it's worse in the UK, overall.

In terms of effective remediation, I commend to your readers the archives at Eide Neurolearning on Dyslexia.

allen said...

Liz Ditz wrote:

One very early clue is a consistent mispronunciation of common polysyllabic words...

I find it difficult to believe that mispronunciation isn't a commonly observed part of acquiring speech. After all, before you get good at something you have go through being bad at it. I can see that it might be a supporting indicator if it persisted beyond some arbitrary age of a perceptual problem but as a primary indicator I think it would give way too many false positives.

Another early clue is an inability to generate rhymes.

That's entirely a new one on me. How strong is that association and how good is the research that supports the association?

Don't mistake a difficulty in processing language sounds with a hearing deficit.

I'm not. I understand the difference but that doesn't undercut the validity of the idea as a means of eliminating hearing deficits as a contributory factor in dyslexia regardless of the point in the sensory path the deficit occurs. If it is contributory then there should be a fairly strong statistical association with the development of dyslexia. Is there?

If I were to guess at the cause of the mirror-image phenomenon I'm familiar with I'd say that it's a developmental problem, that the part of the brain that processes left-right imaging isn't fully developed and sometimes can't decide if the letter is a "d" or a "b".

With adults the problem seems to disappear as soon as the reader appreciates it. Phonics, by providing a set of reliable rules, causes the novelty of words like "bog" to stand out when inappropriate (the bog at my homework) against the words which the reader confidently pronounces. The exceptions draw the readers attention and on inspection the word is usually pronounced properly.

It's the confidence inspired by a reliable set of rules that isolates the unusual word generated by the perceptual problem. I'm not sure if children would respond as quickly to the feedback that's part of phonics instruction but in adults that feedback causes the problem to disappear very quickly. Sometimes in a single session which indicates to me that the underlying physical problem is gone but the lack of confidence in their reading skills causes the problem to persist.

KDeRosa said...

My understanding is that the positioning of objects rarely affects the identification of an object in everyday life. A chair is a chair no matter what orientation it's in. But the letters b, d, p, and q aer all basically the same the object in different orientations. It shouldn't be surprising that same kids don't pick up on this feature of letters unless it is explicitly and clearly taught to them.

Anonymous said...

This is not new information-- it has been known for years that dyslexia is fundamentally a phonological problem. It's just now making its way into the popular press.
http://www.schwablearning.org/articles.asp?r=35
http://www.ldonline.org/article/6254


This is one area that the research is actually very good. Of course, it is coming out of cognitive psychology and neurology, not schools of education.

John, you don't seem to be clear on study design. First, you don't need a dozen double blind studies on anything. That's overkill. Second, a double blind placebo control study on dyslexia? To determine causes? That doesn't make sense. You do double blind placebo controlled studies to evaluate interventions, not determine causes and risk factors. Observational studies (case control or longitudinal studies, typically) are the appropriate study design for figuring out the determinants of the condition. Then you design appropriate interventions, based on hypotheses generated from the epi studies, and then you do the randomized trial.

Anonymous said...

I Speak of Dreams

Charles Fox, who is an attorney and writes the Special Education Law Blog, has a post today of interest to parents of students with dyslexia/reading challenges. Here's the opening:

Guided Reading: Is It Really Appropriate for Students with a Reading Disability?
by Lisa Hannum

The following post is from a collegue who is special education advocate, a trained mediator, and past President of the Illinois Chapter of the International Dsylexia Association. She has a great deal of expertise and experience in the area of reading methodologies and knowledge of needed remediations for reading-based disabilities. She has written this post on the subject of guided reading, at my request, since many schools [mis]represent that Guided Reading is appropriate to teach student struggling with a reading disability.


Link:

Guided Reading.

Second post--here's the opening:

A Structured Language Program to Address Reading Disabilities By Lisa Hannum

This is the second post from my colleague Lisa Hannum addressing the essential elements of Structured Language as the primary means of reading remediation, in contrast with Guided Reading which was discussed in the post from the previous day.

A structured language program teaches more than the sounds of the 26 letters of the alphabet. It teaches the concept of phonemes and graphemes. Phonemes are sounds in language. Graphemes are the letter or letter combinations that represent the sounds in words. For example, in the word cup there are three sounds, represented by three graphemes: /c/ /u/ /p/ (letters within / / refers to the sounds). In some words, there is a one-to-one relationship between sounds and letters. In other words, that relationship is not as simple. In the word chirp there are three sounds (/ch/ /ir/ /p/) These three sounds are represented by three graphemes, but five letters. Both letter and letter combinations can represent individual sounds. (Think of the complexity of a word like eight. There are only two sounds, /eigh/ /t/. The grapheme “eigh” is pronounced like the “a” in ape.)


Link:
Structured Language Program

It might be worthwhile for interested readers to print out these two posts and share them with their schools/teachers.

Allison said...

I have a problem hearing the difference between "ph" and "th" syllables (are those phonemes?)

If I don't know the context, I can't distinguish them. This phenomenon is most clear when I hear names of composers or songs on the radio, and I'm unfamiliar with the name. This phenomenon exists well enough that surely you'd find the correlation between people with auditory issues like mine and dyslexia if such really exist.

Even assuming this correlates to some versions of reading trouble, what does this have to do with the "I mix up knowing the spatial difference between d/b or p/d" ?

My son, not yet 2 years old, gets awfully confused right now by 6 and 9. Why? Because he rightfully recognizes that an upside down 1 is still a 1. How do I know? Because when he sees an upside down 1, he yells "1!" Same with a 2. and a 4. With 3, he yells "E" at times.

So I try to teach him that "this way, we call it a 6" and "this way we call it a 9". I don't have better words to use to explain why rotational invariance doesn't work on 6 and 9 but does on 7 and 2. Likewise, he doesn't comprehend the difference between 1 and lower case l. Fonts are confusing. This whole upper and lowercase this is madness.

But does it mean something is wrong with the child's mind? Or something is wrong with his teaching? Not yet. But by 5, it would mean I hadn't trained him properly.

last thought: I just read a school district web site that told me "dyslexia can't be properly diagnosed until 5th grade". Really. Is that because if you learn to read in 4th grade but not before then and have no difficulties, you suddenly weren't dyslexic? uh huh. Mostly it means that they've stopped trying to wait you out--they never bothered to remediate you, and by 5th grade, it's too late. so now you have dyslexia.