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On the Reality of Dyslexia

12/13/2019

 
There was a mild kerfuffle on Twitter about some comments made by literacy researcher Dick Allington; he made some not-very-academic remarks about people with whom he disagrees (see here). Much of Alligton's work is serious, but this didn't strike me as serious, so I merely made a joke about it on Twitter, but a few people replied in earnest, among them this one
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Allington is quoted in the article as saying he's "reasonably sure" dyslexia doesn't exist. It's a valuable question: what's the basis for considering dyslexia different than just "bad at reading?"

Presumably, we’re going to measure a child’s reading proficiency with a test, and a score below some cut-off will make us suspicious that the child is having a specific reading disability. Sounds simple enough, but there’s a problem. The figure shows two graphs depicting imaginary data from 10,000 first graders. In panel A, there’s a bell curve on the right, which we would call typical readers and then to the left a smaller number of readers who are impaired. There’s no mistaking that this second group is different than the first, so choosing a cut point—a point at which you say “score below here, and you probably have dyslexia” is straightforward; I’ve marked it with a star.
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But scores on reading tests don’t show the pattern you see in panel A. They show one bell curve, as in panel B of the Figure.  I can still create a cut-off score—below there, and I’m saying you have dyslexia—but the justification is less clear. We’re describing “dyslexia” as though it’s a quality, a feature of the child, something we can point to. So the child with dyslexia is supposed to be different in kind from the typical child, but you can see the problem.  How confident am I that a child just below my cut-off score is really different than the child just above it? 

So is dyslexia even real? Maybe it’s more accurate to say “these are the kids in the bottom 10% (or whatever) on this measure.” Why label them “dyslexic?”

Although any cut score will lead to some errors, it’s not the case that it’s a completely arbitrary line. There is something different about many of the kids in the left tail of the graph. That’s important because it makes us want to be more active. Saying “well, there’s always going to be someone who is the worst at reading” sounds like we’ve given up. But if you accept that the child is facing special challenges, it invites searching for a solution. So what makes us think kids with dyslexia are different than typical kids?

First, there is a genetic component. The incidence of dyslexia in the population is about 9%. But if a child has a parent with dyslexia, the chances the child will too are about 35 or 40%. (Pennington et al., 1991). Of course, that high figure may be a consequence of the dyslexic parent offering a less supportive literacy environment than other parents do. Better evidence comes from studies comparing identical and fraternal twins. Twins of each type are likely to attend the same school and be exposed to similar home environments, but identical twins share 100% of their genes, and fraternal twins only 50%. If a child has dyslexia her fraternal twin has a 38% chance of having it too. But an identical twin has a 68% chance of having it (Defries & Alarcón, 1996).  Of course the fact that there is a genetic contribution doesn’t mean that ones genes amount to an inevitable reading destiny. Children with dyslexia can become good readers—it will just take more work.

Here’s another reason to think that dyslexia is real: kids show subtle signs of a problem before reading instruction begins (e.g., Guttorm, Leppanen, Richardson, & Lyytinen, 2001; Lyytinen et al., 2004; Richardson, Kulju, Nieminen, & Torvelainen, 2009). These studies examine children from families where one of the parents has dyslexia. Researchers test how these children hear and use language when they are quite young, and then wait for them to get older. Then they note which children struggle with reading and which do not and look back at the data collected when they were younger. The two groups show differences very early in life. At birth, the parts of their brain that handle sounds show different responses to human speech.  At age two and a half, children who would later have difficulty learning to read speak in shorter, less syntactically complex sentences, and their pronunciation is less accurate. At age three, they have a smaller vocabulary. At age five, they show deficits in phonological awareness, and they know the names of fewer letters.

A third point regarding the “reality” of dyslexia; we know that it’s not simply a delay, a byproduct of the fact that kids develop at different rates. There’s no doubt that some children learn to read faster than others, but kids identified with dyslexia don’t catch up without intervention. The kids who read poorly in early elementary school continue to struggle unless they get help (Scarborough & Parker, 2003; Shaywitz et al, 1995). Children with a disability can grow up to be good readers but even they show residual problems like slower single-word recognition and problems with spelling (Bruck, 1990; Maughan et al, 2009).

So here’s the way I think about the “reality” of dyslexia. It’s not a disease in the sense that measles is a disease; you have it or you don’t. Rather, we start with the theoretical claim that reading ability is a product of the home environment, teaching at school, and some ability-to-learn that is within the child. Dyslexia is a problem in the child’s ability to learn (restricted to reading and closely related to other language tasks). The three findings I’ve just listed are consistent with the idea that some children do have a specific ability-to-learn problem; but that doesn’t mean the problem is present or absent. The severity of the problem runs on a continuum, so in that way it’s more like high blood pressure or obesity. And like those problems, the fact that there’s not an obvious cut-point at which you can say “you have the disease, but you don’t” doesn’t mean that we shouldn’t take it seriously.

References
 
Bruck, M. (1990). Word-Recognition Skills of Adults With Childhood Diagnoses of Dyslexia. Developmental Psychology, 26(3), 439–454.

DeFries, J. C., & Alarcón, M. (1996). Genetics of specific reading disability. Mental Retardation and Developmental Disabilities Research Reviews, 2(1), 39-47.

Guttorm, T. K., Leppanen, P. H. T., Richardson, U., & Lyytinen, H. (2001). Event-Related Potentials and Consonant Differentiation in Newborns with Familial Risk for Dyslexia. Journal of Learning Disabilities, 34(6), 534–544.

Lyytinen, H., Aro, M., Eklund, K., Erskine, J., Guttorm, T., Laakso, M.-L., … Torppa, M. (2004). The development of children at familial risk for dyslexia: birth to early school age. Annals of Dyslexia, 54(2), 184–220.

Maughan, B., Messer, J., Collishaw, S., Pickles, A., Snowling, M., Yule, W., & Rutter, M. (2009). Persistence of literacy problems: spelling in adolescence and at mid-life. Journal of Child Psychology and Psychiatry, 50(8), 893–901.

Pennington, B. F., Gilger, J. W., Pauls, D., Smith, S. A., Smith, S. D., & DeFries, J. C. (1991). Evidence for major gene transmission of developmental dyslexia. JAMA, 266(11), 1527-1534.

Richardson, U., Kulju, P., Nieminen, L., & Torvelainen, P. (2009). Early signs of dyslexia from the speech and language processing of children. International Journal of Speech-Language Pathology, 11(5), 366–380.

Scarborough, H. S., & Parker, J. D. (2003). Matthew effects in children with learning disabilities: Development of reading, IQ, and psychosocial problems from grade 2 to grade 8. Annals of Dyslexia, 53(1), 47-71.

​Shaywitz, B. A., Holford, T. R., Holahan, J. M., Fletcher, J. M., Stuebing, K. K., Francis, D. J., & Shaywitz, S. E. (1995). A Matthew Effect for IQ but not for reading: Results from a longitudinal study. Reading Research Quarterly, 30(4), 894–906.
Bonnie Shaver-Troup link
12/13/2019 02:01:04 pm

What a thoughtful and balanced article! Your last paragraph motivated me to reach out to you today.

Previously, as an ed therapist, I focused on dyslexia and 20 years ago created the 7 Lexend fonts- available since August 2019 on Google Fonts and Google Docs (Click More Fonts)- as a reading performance solution for dyslexia and struggling readers.

My first school study using Lexend was in early 2000s with 2nd-8th grade students at a SF Bay Area school for students identified with dyslexia- the avg ORF (not test/retest) improvement was 47%. This is an IMMEDIATE improvement achieved by changing font factors, including size, shape and spacing. Across the 20 years, Lexend has been found to improve reading performance not just for those with dyslexia and struggling readers, but across the continuum, including for our most high performing students- in fact, this is why I address the issue as print sensitivity. Although print sensitivity sounds simplistic it is a complex relationship of factors.

I would be thrilled to speak with you about our shared interest in reading performance, Lexend results and why Lexend works. We need more solutions.
https://www.lexend.com/
https://fonts.google.com/?query=lexend&sort=alpha

Dyslexia Advocate
12/14/2019 07:14:47 am

Thanks for your thoughtful remarks. One point that is not mentioned in your analysis of the left tail of the curve, is a comparative analysis of the students intellectual aptitude. If dyslexia doesn’t exist, how would we understand students from a high literacy environment , with above average IQs, who are a standard deviation or more below the mean in reading achievement?

Anna M.T. Bosman (Radboud University, Nijmegen, The Netherlands) link
12/15/2019 03:54:46 am

Somehow, we have been puzzled by the fact that a relatively smart child (whichever way determined) has more problems acquiring reading and spelling skills than a less smart child. The assumption is that when you are smart, you are not supposed to have difficulties in the acquisition of literacy. Why would that be?

My tentative answer is that because most children learn to read without too much trouble, learning to read can’t be very difficult. Thus when you are smart and you don’t learn to read that easily, you must suffer from a disorder. But learning a skill is not generally easy or difficult; learning a skill is difficult or easy for someone. Why is it surprising that an otherwise smart child has more problems learning to read than a less smart child, is because this skill proves to be difficult for him or her.

We are not surprised when the smart kid does not do very well in sports or the visual arts, despite the fact that less smart kids outsmart him in these domains. Somehow being a good athlete and not so smart is not surprising, but being smart and not so good in reading is. I believe that we best approach the problem of acquiring any skill as something that is particular to the individual. This means that a so-called ‘smart’ child may or may not experience some difficult with the acquisition of learning to read and spell.

If we accept that all children (and adults) come with a different set of talents that do not necessarily correlate highly, sometimes they do, but often they don’t, than there is no need for attributing disorders to anyone. We would not diagnose a child with dyslexia and give the child the impression that there is something wrong with him or her. Wouldn’t it be more helpful to induce in the child the attitude that if I do my best that I will learn this; it may take a bit longer than it takes most children, but in the end I will get there.

Think about this: If being sporty was more important in modern-day society than being able to read, we would not have diagnosed children with dyslexia, but with dysathletica.

Jeff McQuillan link
12/14/2019 12:57:05 pm

I appreciate your succinct summary of the dyslexia arguments here. I remained unconvinced by the three points you make.

1. The basic assumption that identical twins raised together share the same environment as fraternal twins has been challenged by several writers. See Gerry Coles’ books (1987, 2000) and more recent work by Jay Joseph (2016). If they are correct, then a good deal of the “genetic” case for dyslexia goes out the window.

2. I came away with a very different impression of the Finnish studies you cite on early oral language differences among dyslexics. I was surprised by just how *few* differences were actually found in their measures. (They are also fond of multiple t-tests w/o any indication that a correction was applied.) But even if those differences are real, an environmental cause is still plausible (one has the same parents and home/community environment throughout).

3. The same environmental variables that might explain 0 to 5 differences can explain persistence of relatively poor reading later on (e.g. Shaywitz et al.’s data). The fact that poor readers in grade 3 remain relatively poor readers in grade 10 is not strong evidence in favor of dyslexia being “located” primarily in the child vs. the environment. Poorly nourished 2nd graders living may still be poorly nourished in grade 10, but no one would argue that "undernourishment" is a diagnosis.

The strongest data for the “reality” of dyslexia would be to show that kids whose “deficits” (phonological, word ID) are “remediated” by grade 3 go on to be better readers than those whose don’t get such remediation. But where is that evidence? Suggate’s (2016) meta-analysis found that the effects of phonics interventions didn’t even last a year.

Blachman, Schatschneider, Fletcher, Murray, Munger, and Vaughn (2014) did a 10 year longitudinal study of an early grade intervention which had lots of phonics. They found that by the time the kids got to high school, they showed differences only on word identification tests, but not in reading comprehension. This suggests that the current view of dyslexia is at best incomplete, at worst based upon faulty assumptions.

Dyslexia Advocate
12/16/2019 05:58:13 am

I’m a little confused about your bell curve A and B. If I understand correctly, you speculate that if dyslexia existed, you’d see a greater cluster or bump at the lower end of the tail. But, if students are tested using standards scores, a normal bell curve distribution will be by definition created. Using a test that measures absolute scores, you might see clusters at any point, but standard scores create a perfect bell curve - or am I misunderstanding something?

Further, you say because reading scores fall along a bell curve, maybe you’re just finding bad readers not dyslexic reading in the bottom percentiles. That to me is like saying if you measure students’ height using a bell curve, the bottom tail are just short kids not those with dwarfism, or other physical conditions impact growth. The point is height is one measure, once you find those at the bottom tail, further analysis is needed to determine the reason for being at that point along the curve. The same is true with reading disabilities. Because some kids may “just” be bad readers doesn’t mean that others are not bad readers due to dyslexia or other neurological/cognitive conditions.

Leslie Buford
1/3/2020 03:36:17 pm

Excellent point! I was searching for the words to articulate the same concept. IT is the difference in processing that justifies the diagnosis, not just the poor reading skills.

Dyslexia Advocate
12/16/2019 06:28:51 am

Anna, you say, “Wouldn’t it be more helpful to induce in the child the attitude that if I do my best that I will learn this; it may take a bit longer than it takes most children, but in the end I will get there.”

In your statement, there is an assumption that doing one’s best will lead to an end result of getting there. But is reading proficiently merely a matter of “doing one’s best?” and where is “there?” Is “there” reading at the same level as one’s intellectual peers?

Do you challenge the notion that intellectual aptitude/cognitive capacity is highly correlated with reading ability ( except among those with dyslexia) but has nothing whatsoever to do with coordination or athleticism?

Were it not for a reading disability, how would you explain students who have high intellectual abilities, as measure by IQ tests, logic and reasoning abilities, who come from high literacy environments, who struggle to acquire reading skills? Students who similarly show red flags with articulation difficulties, inability to rhyme, etc prior to formal schooling. What explains their difficulties acquiring theses skills, if not dyslexia or some other neurological deficit?



William Brown
12/17/2019 08:20:40 pm

Around 1995 I authored a study of the reading score distribution in a major urban school district. The results, which were presented to the state legislature, showed a bimodal distribution.

We concluded that the problem was the district wide use of Whole Language reading instruction. Most students learned to read fairly well with that kind of teaching. A significant number of students, however, were significantly behind the majority of students, forming a smaller bell curve at the lower end of the spectrum.

I presented these results to an IRA conference in Des Moines Iowa. The audience was impressed with the report, but not all of them agreed with the diagnosis.


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