Home > Learning Disabilities > What Causes Dyslexia?

What Causes Dyslexia?

By: Miriam Vered - Updated: 5 Dec 2012 | comments*Discuss
Dyslexia Brain Scanning Phonemes Read

The word dyslexia comes from the Greek language, one of mankind's most ancient languages and it seems likely that the condition has been around for a long time too. Spoken language is believed to be an innate skill of the human brain, derived from millennia of evolution. But reading was probably invented around 5,000 years ago, so, as far as human history goes, it's relatively new, and as such is not an inborn ability like speech, rather one that must be actively taught and learned. This may be the reason why about 5% of children's brains seem to be hardwired in such a way that they struggle to acquire the reading skills that the other 95% master relatively smoothly in societies with universal education.


Dyslexia runs in families, and there is often left handedness somewhere in the family as well. So it seems that genes are involved, but nobody knows which genes yet, and inheritance cannot be predicted.

What's Happening Inside the Dyslexic's Brain?

Improved brain scan technology has helped researchers to reveal some interesting avenues of research into dyslexia. For example, clusters of cells that lie on the surface of the left and front brain (areas that are important in reading and writing), in non dyslexics have been found to lie beneath the surface in dyslexics. Theories have been suggested that these cells (which are called ectopic) failed to make the journey that they should have when the foetal brain was developing before birth. The magno-cellular system is a part of the brain which is involved in our capacity to see moving images. Some studies have shown that this part of the brain may be smaller in dyslexics, which may lead to difficulties in the process of interpreting the images of words that the eyes see.

EEG (electroencephalogram) involves application of electrodes to the head, then interpretation of the measured electrical activity, or brain waves. When a child is beginning to learn to read, EEG activity is greater on the right side of the brain. In a proficient reader, there is more activity on the left side. In dyslexics, there are different variations in left-right activity. It has been suggested that dyslexic children have to use their right brain in language work which the left brain handles in non dyslexics. As the right brain is not believed to be hard wired for language work, after the beginning stages, dyslexics may have to work far harder than non-dyslexics to acquire similar reading skills.

PET (positron emission tomography) scans have been taken of the brains of dyslexics and non-dyslexics during reading. In the comparison, an area of the left temporal lobe is found to be far less active in dyslexics, suggesting that abnormalities in this region may be involved in causing dyslexia.

Can Hearing Problems Contribute to Dyslexia?

When children have repeated colds and ear infections, if appropriate measures are not taken to correct the situation, their hearing may be impaired, and this may, in turn affect their development of phonological awareness (sensitivity to sounds as they relate to the letters of the language).

Having said that, the degree to which hearing problems can contribute to dyslexia is controversial. There is evidence that in general, dyslexics do worse at lots of hearing and listening tasks than non-dyslexics. But the problems are often not related to speech perception, so the data are hard to interpret. It seems that hearing problems may contribute to the dyslexia only in a small subset of dyslexics. Most researchers believe that for the majority of dyslexic children, the important underlying defect lies in the specific part of the brain that deals with phonemes (sounds of words).

Is English to Blame?

Brain scanning studies have shown that the connections between different areas of the brain that deal with language processing work differently in dyslexics compared to other people. They lack the capacity to process phonemes (language sounds), so they can't draw inferences about words in the way that most people do automatically. When English speaking children learn to read, they effectively have to individually and consciously commit to memory the over 1,100 ways that written letters symbolise 40 sounds. The language is notorious for its inconsistencies, as evidenced by words where the same letters are pronounced differently like cough, bough, dough and tough; or chat, chute and scholar. On the other hand, sometimes different letters are pronounced the same way, like the "sh" sound in ship, initial, and machine.Children learning to read and write in English take a longer time to acquire their language code than do children learning most other languages.

This is probably the reason why there are over twice as many dyslexics identified in English speaking countries, compared to countries with simpler languages, like Italian, where there are 33 sounds, spelt with 25 letters. This means a more or less one-to-one relationship between letters and sounds, and the rules for pronunciation and stress are consistent.

Studies have shown that dyslexic Italians are better at reading their native language than are dyslexic English speakers, despite similar poor scores on standard tests for short term memory of verbal sounds, and similar abnormalities in how their brains process information, according to PET scans. In fact, many Italians may live their whole lives in ignorance of the fact that had they would have been dyslexic, had they lived in a country whose language had a more complicated phonology!On a similar note, a fascinating case was reported of an American child who grew up bilingual in Japan and turned out to be dyslexic in English but not in Japanese, a language whose whole writing system is fundamentally different from English, yet phonologically simpler.

So it seems that not just genetic roulette, but also the luck of the geographical draw can greatly affect the life of someone who happens to be born with the potential for dyslexia.

You might also like...
Share Your Story, Join the Discussion or Seek Advice..
Why not be the first to leave a comment for discussion, ask for advice or share your story...

If you'd like to ask a question one of our experts (workload permitting) or a helpful reader hopefully can help you... We also love comments and interesting stories

(never shown)
(never shown)
(never shown)
(never shown)
Enter word:
Latest Comments
  • Aawwmmm
    Re: Savant Syndrome
    That's so cool I would be more impressed if you told me you spoke with other individuals while you were sleeping or even comprehend that there are…
    20 August 2017
  • Alex2017
    Re: Obsessive Compulsive Disorder
    Hi, for many years now I am suffering severe ocd. I cannot drive car anymore, and also I get some new symptoms. Things I struggle…
    24 April 2017
  • Alex
    Re: How Does Language Acquisition Happen?
    This is a very one-sided article and only takes a nativist view into account, can be misleading for someone who has no…
    21 January 2017
  • Soulless
    Re: Savant Syndrome
    I've been able to dream the future since I was a child. Others have always told me it's just deja vu or they'll congratulate me on having a grand…
    23 August 2016
  • bj17
    Re: Literacy and Your Brain
    Does anyone have the source for more information on the changes in the brain as guerrillas learn to read?
    11 February 2016
  • pampam
    Re: How to Get Great Exam Results Using Exam Technique
    pls can some one tell me the clues to pass my exam and be the first am tired of 7th position
    29 January 2016
  • Abraham
    Re: Is Intelligence Inherited
    Peter, your comment is a sign of being not intelligent. Otherwise by that logic we'd all have black skin...Two words, GENETIC…
    3 December 2015
  • freckles
    Re: How Long Do Young Children Take to Process Information?
    I had brain trauma as a child from the age of ten yrs oldafter falling from a swing park shute…
    29 November 2015
  • BrainSkills
    Re: How to Develop Empathy Skills
    Andrea - Your Question:Hello, my partner doesn't understand what empathy means, and he doesn't know how to explain his feelings…
    27 November 2015
  • Andrea
    Re: How to Develop Empathy Skills
    Hello, my partner doesn't understand what empathy means, and he doesn't know how to explain his feelings either. I've tried to…
    25 November 2015
Further Reading...
Our Most Popular...
Add to my Yahoo!
Add to Google
Stumble this
Add to Twitter
Add To Facebook
RSS feed
You should seek independent professional advice before acting upon any information on the BrainSkills website. Please read our Disclaimer.