One dyslexia… many dyslexia ?

“Dyslexia is a learning difficulty that primarily affects the skills involved in accurate and fluent word reading and spelling.” Sir. Jim Rose

If several years ago, dyslexia’s awareness in society was not well informed, today, everybody know, at least, that it has to do with brain and reading. For a long time, we believed it was a intelligence problem. We now know that learning disabilities are disorders that can affect various brain processes involved in the learning procedure but are defined when one has at least average intelligence. It means that this concept excludes any one whose learning problems originate in any visual, hearing or physical handicaps, mental retardation, emotional disturbance or environmental, cultural, or economic disadvantage. Today, many research teams are still trying to better understand dyslexia and its causes by investigating brain’s functioning.

One interesting point that is nevertheless rarely mentioned in that topic is that dyslexia is not the same for everybody. This statement was already suggested by H. Myklebust in 1965. He mentioned 2 different types of reading difficulty : some “could not acquire the auditory equivalents of the appearances of te letters” (which is now know as “phonological dyslexia”) and others were anable “to mentally visualize letters and sounds” (which we now call “surface dyslexia”). Over time, researchers have continued to investigate this hypothesis of dyslexia subtypes existence.

All reasearch’s assumptions of this kind are always established from observations and models. In this case, it is based on what we know from the reading system, which model evolved over time, as science moved ahead. The reading model presents the different components of the reading system that one should learn and have to be skilled reader. Today, the widely accepted by resercher’s community model of reading is the dual route model (at least for single word reading). This model is presented below.

Now, when you have the model of intact adult skilled reading, you can imagine that any of its components can be individually impared. That helps you understand that depending on which part of the system is impaired, the difficulty induced will be different. Such selective impairments produce some particular patterns of preserved and impaired reading abilities.

Starting from this and based on the dual route model, Naama Friedmann, an israel researcher worked on the exploration of the dyslexia subtypes that should be observed from the different possible pattern of impairments. She worked on arabic, hebrew and italian languages to identify these and found out 19 different types of dyslexia.

I will not give details on those dyslexia subtypes because it would take another full article (to come later ?). But if one wants to read more about N.Friedmann’s work, you would want to read her publications (here) and watch her very good conference that she gave during the seminary “Specific disorders of the cognitive development” that took place in the Collège de France in February 2015 (here).

I would like to focus on one last special side of her work that is, in my opinion, worth to consider : how can we distinguish the different subtypes of dyslexia now that we know there are several ?

N. Friedmann examined this issue and developed, to this end, a words list each one of them selected for specifically inducing certain types of reading errors. To diagnose our exact dyslexia, we are asked to read this list of words. Depending on the rates’ repartition of each types of reading errors we made, we can now identify it.

This precision N. Friedmann brings to dyslexia diagnosis is a crucial step forward for the life of dyslexic children and their education. Indeed, even if dyslexia is today easily diagnosed and treated, remediations and offset tools remain poor and not as efficient as a child would need, especially in classroom settings. Knowing more precisely the specific characteristics of the dyslexia one has would help speech therapists, teachers and parents finding the appropriate and most effective treatment and tools.

To end-up, French researchers from the Unicog laboratory of Neurospin have just joined the team to adapt this test for the french langage. We can therefore have hope that in a few years, in France, the treatment for dyslexic children will be much more efficient and will allow them to pursue their dreams by alleviating their difficulties.

Dys-add.com. (2016). Bright Solutions | What is Dyslexia?. [online] Available at: http://www.dys-add.com/dyslexia.html [Accessed 16 Jun. 2016].

Friedmann, N. (2015). Diagnostic et remédiation des différents sous-types de dyslexie.

Friedmann, N., & Coltheart, M. (in press). Types of developmental dyslexia. In A. Bar-On, & D. Ravid (Eds.), Handbook of communication disorders: Theoretical, empirical, and applied linguistics perspectives. Berlin, Boston: De Gruyter Mouton.

Friedmann, N., & Lukov, L. (2008). Developmental surface dyslexias. Cortex, 44, 1146–1160.

Rose, J. (2009). Identifying and teaching children and young people with dyslexia and literacy difficulties. Available at: http://www.education.gov.uk/publications/eOrderingDownload/00659-2009DOM-EN.pdf[Accessed 16 Jun. 2016].