kitchen table math, the sequel: dyslexia is visual not phonological - ?

Saturday, August 28, 2010

dyslexia is visual not phonological - ?

A few years ago, when I asked Daniel Willingham what journal I should read on the subject of cognitive science, he recommended Trends in Cognitive Sciences.

Yesterday, as I was trawling the journal for articles on habit learning, I came across an article from January 2010:  Dyslexia: a deficit in visuo-spatial attention, not in phonological processing by Trichur R. Vidyasagar and Kristen Pammer.
Developmental dyslexia, a specific difficulty in reading despite adequate learning opportunities, affects from 5 to 10 per cent of the population [1], but there are many manifestations of reading failure (Box 1). The etiology of dyslexia itself has been hotly debated for a long time. Theories have ranged from the reading disorder being a high-level learning disability, to a visual perceptual defect. Although it is generally recognized that a majority of poor readers have severe problems in phonological awareness [2,3], it is still an open issue whether the causal deficit in dyslexia is necessarily phonological. The debate is particularly timely in light of recent reevaluations – especially in the USA, Australia and UK – of how children learn to read.

In this paper, we present evidence for an alternative possibility, namely that a fundamental defect in the visual pathways, with or without a corresponding defect in the auditory system, can potentially cause a cascade of effects that can ultimately manifest as a reading problem, including phonological impairments. Understanding the mechanisms underlying dyslexia allows better informed policy making with regard to teaching and remedial intervention.


Pre-reading phonological skills predict later reading failure, and phonological interventions have been demonstrated to be successful [2]. However, there are a number of reasons why poor phonological coding might not be the whole story, or even be an etiological factor in dyslexia. Some cases of dyslexia are clearly not phonological, for example where the reading errors are for irregular words, not non-words, and impairments in reading non-words are not always matched by deficits in phonological awareness [4,5]. There are reports of children [5,6] and adults with brain damage [7,8], who have difficulties in non-word reading but nevertheless exhibit good phonological awareness. Such evidence should, at the very least, lead us to question the causal link between a phonological deficit and dyslexia.


Misordering of letters and reversal of letters in a word are common complaints from dyslexic readers, and sensitivity to spatial sequencing of the constituent components of text-like object arrays predicts reading in adults [12] and children [13]. Such difficulties in ascertaining the sequence of letters in words cannot be easily explained by phonological deficits. Studies of neurophysiological bases of pattern and object recognition indicate that such sequencing of letters is a non-trivial problem for the brain.

Trends in Cognitive Sciences Vol.14 No.2

reading on iPhones and Kindles


Anonymous said...

Why do people think that dyslexia is a single disability with a single cause? It is a symptom that can be caused by a huge variety of different underlying problems. Figuring out which underlying problems are the causes is essential for proper treatment or remediation, but looking for a single silver bullet is an exercise in futility.

Catherine Johnson said...

I never thought the phonological deficit theory could possibly be the whole story - at least not after talking to Thomas Zeffiro at a NAAR meeting years ago.

But even without talking to Zeffiro, I didn't see why it made sense to say that dyslexia was **not** a problem in the visual system. You have to see the letter in order to read, and as far as I know the visual system can go as wrong as any other function of the brain or body...

Liz Ditz said...

The questions: "Is dyslexia always a problem with the visual system?" vs. "Is dyslexia never a problem with the visual system?".

Then there's the rapid automatic naming issue. In other words, when presented with a visual stimulus (such as a letter) is the recall of the sound sufficiently fast?

I'm with gasstationwithoutpumps:

Reading is a very complex interplay of cognitive activities. Disruptions in those activities will affect the acquisition of reading mastery.

And let's not launch into (a) individual child factors, such as deficits in oral/verbal language or (b) dysteachia.

Kevin said...

I also agree with gasstation on the idea that dyslexia is caused by multiple things but one major issue is not teaching decoding properly.

The best summary of the Dolch sight words is that they are extremely common words that have to be read automatically for a student to be able to understand any English text. However, they are often taught incorrectly as words that cannot be decoded, causing at least some cases of dyslexia. Decoding is not the whole story because some dyslexic people have visual problems while reading and in other activities. in fact, there is a disorder called Irlen Syndrome that categorizes the visual disturbances observed. Colored overlays have been shown to help dyslexic people in reading.

hayesatlbch said...

Visual issues that make reading difficult are present in a minority of dyslexics. Auditory and language processing problems are more common and affect a majority of dyslexics.
Multiple distinct problems from multiple distinct sources.

Dyslexia is complex and complicated and so it is hard to understand and describe. Rather than take the easy way out and choose your favorite symptom and make it the cause of dyslexia and then fight to the death to convince others you are right ( not this blog,but many), consider dyslexia as a syndrome.

Then dyslexia can be understood as a condition (syndrome) where every dyslexic has some reading difficulties but may or may not have each of a long laundry list of specific symptoms which everyone has seen.

There is real value to understanding dyslexia as a syndrome because it changes dyslexia from the failure of trying to fit all dyslexics into a one size fits all theory into a focus on whether or not the individual has issues with each particular problem from those laundry lists. Only those issues specific to the individual need to be addressed for the individual.

Every preconceived idea that dyslexia has a single cause is sure to fail some individuals. As a syndrome ,identification of individual areas needing help should develop better interventions for each dyslexic.

Susan said...

See -Myth: Dyslexia is a visual problem

'Facts: Prof. Vellutino showed this was incorrect when he 'asked dyslexic and non dyslexic American children to re-produce Hebrew letters none of them had seen before... the poor readers performed as well as the normal readers in reproducing Hebrew letters from memory...Absolutely no differences between the two groups. If anything the normal readers made more errors than the poor readers, so the poor readers could see the materials as well as the normal readers' (Mills. The Dyslexia Myth)'

The Cambridge University effect is an internet myth.

hayesatlbch said...

"See -Myth: Dyslexia is a visual problem"

Notice that the difference is between groups. It is only the one size fits all, every dyslexic suffers from the same cause and IMO soft science educators and psychologists trained with the idea that the answer has been found when there is agreement in a majority of the studied population. That type of research has problems identifying minority factors such as visual dyslexia.

That visual dyslexia is found only in a minority of dyslexics is no reason to say it does not exist. That it does not exist as a primary problem for a majority of dyslexics is true. There is a real and important difference in the last 2 statements.

Try telling the dyslexic that says" I could read if only the words would stay still" that their problem is not visual.

If the differences that determine dyslexia could be identified by studying groups then dyslexia could be identified by MRI. Whoops every MRI study of particular areas of the brain has reached the same result : differences are seen between groups with so much overlap that individuals can not be identified as dyslexic or not.

The study you reference is not very sophisticated or persuasive to me. Actually the most recent visual / dyslexia studies using visual noise do indeed show a much stronger relationship between vision and dyslexia. I suspect the relationship between dyslexia and vision in those studies is higher than actual because visual processing problems ( as occurs with other dyslexia problems) are inferred to be visual thus skewing the results to the high side because of a systemic analysis error.

Here is a clue to understanding visual dyslexia. If the person says their reading difficulties are caused by visual difficulties seeing the text their problem is VISUAL.The majority of dyslexics report no visual problems but some do.

Catherine Johnson said...

Then there's the rapid automatic naming issue.

right - and I don't know whether this study talks about RAN

btw, I should add that I'm still learning about dyslexia; I don't have a 'position' on what it is or isn't (or what the balance is).

I buy the finding that there is a visual component (always? sometimes?) for the reasons I mentioned above...

Catherine Johnson said...

btw, years ago I was prescribed a medication that caused me to reverse letters!

It was the damndest thing; I had never experienced anything like it.

It was quite disabling, too.

One day I drove way out into the valley (we were living in Studio City) to get to a store selling children's clothes I liked.

When I got to the address, I was in on a neighborhood street, parked in front of a private residence.

I figure I had to be in the wrong place, so I checked and re-checked the address on the house & the address on the ad, and they matched.

Finally I got out of my car and walked up to the house & nearly got assaulted by a couple of Dobermans who clearly didn't think I had any business trying to buy children's clothing from the owner.

I gave up and went home ----- at which point I **finally** discovered that I had reversed the digits in the address. The address was printed properly on the page; I had reversed them in reading the number -- and I had done this several times in a row, while sitting out in front of the house.

I also had several experiences of reversing digits while reading, which I knew I'd done because I knew how to spell the words.

When I stopped taking the medication, the effect went away.

Catherine said...

This was really interesting to me since my son is dyslexic and is about to have an evaluation for visual therapy later this week. He's already had some intensive phonics work, so his reading is much better, but it's still hard work for him. I can't really comment on this from an academic point of view (my area is family medicine, not education or neurology), but it was encouraging that at least some dyslexics have visual issues. We'll see if visual therapy is an option for my son, and if it helps!



Catherine Johnson said...

Catherine ('other Catherine,' I should say) - if you're still around - let us know how it goes.

I've been intrigued by visual therapy for years, after having seen Melvin Kaplan (I think that is his name) give an amazing presentation here.

Three of us had visual therapy with Dr. Kaplan for a time (Jimmy, C., and me) but it was so difficult to keep up with the 'homework' that I could never tell whether we were making headway.

We saw some pretty remarkable results right away with C. on the soccer field, interestingly enough. He was young at the time. Maybe 9 years old?

Catherine Johnson said...

The book to read about Dr. Kaplan is Ricki by Frederic Flach.

Dr. Kaplan's book is: Seeing Through New Eyes: Changing the Lives of Children with Autism, Asperger Syndrome and other Developmental Disabilities through Vision Therapy

Erin Johnson said...

While the auditory component of decoding is essential, a completely underappreciated component of decoding is visual tracking (in a linear fashion across the page in a straight line) and grouping letters to represent one sound.

Pirwhaps ibt miebt bee healpphull tue ghivv a deammonnstracian abowbt whou ghrooping and trakking affekt reedding abillittee.

(Perhaps it might be helpful to give a demonstration about how grouping and tracking affect reading ability.)

I have a difficult time reading the demonstration because I have to slow down to group the letters into their respective sounds (and I wrote it!).

Readers all need to parse letters and associate those letter groupings with the associated sounds. That parsing is non-trivial.

hayesatlbch said...

The reasoning behind the validity of vision therapy seems to be that because a few people have been helped that all people with learning disabilities will be helped.

The high failure rate combined with no financial guarantee makes for a business plan that can be described as "Take the money and run".

10% is the generally agreed upon % of dyslexics with non-phonological reading problems (I.E. visual dyslexia) where visual difficulties seeing text is a primary cause . There are some dyslexics with co-existing visual and phonological problems but the majority of dyslexics do not have any visual problems.