Bonus Myth 13 – Dyslexia is hereditary

We reposted an excellent list of the 12 Myths of Dyslexia from the Promethian Trust here: http://communityreading.org/wp/the-dirty-dozen-12-myths-about-dyslexia/

 

Bonus Myth:  Dyslexia is hereditary.

Dorothy Bishop, one of the leading researchers in the genetics of dyslexia outlines the faint evidence of a link between dyslexia and genetics in an excellent blog post.  She has this to say:  “… talk of a ‘gene for dyslexia’, or genetic screening for personality or ability are seriously misguided”

But there are other reasons to dismiss a search for a genetic link to dyslexia.  If there was one, then dyslexia would be a problem for all humans with a genetic disposition, and dyslexia would show up in other languages.   The truth is that ONLY English readers suffer from high rates of dyslexia.

Around 1993, Heinz Wimmer, an Austrian psychologist, was hoping to duplicate the famous Torgesen dyslexia study.  He went around to the schools and recruited the worst readers, but a problem arose immediately in the screening tests; his readers were making almost no mistakes – they were hitting ceiling on accuracy, and were merely slow, unlike English-speaking dyslexics who both read slowly and make many mistakes.  Low fluency turns out to be the main symptom of German-speaking ‘dyslexics’.

The following year, a followup study (Wimmer & Goswami, 1994) compared normal German and English students between the ages of 7 and 9.  They found that the youngest German readers were more accurate than the oldest English ones, and even the slowest young Germans were faster than most older English readers.

By English standards, there are no German dyslexics.   By German standards, almost EVERY English reader is dyslexic.

What about other languages?  Consider Italians: Paulesu et al. (2001) conducted a brain-scan study of English, French, and Italian dyslexics.  In order to match for age and IQ, Paulesu had to find university students with dyslexia – not easily done in Italy where dyslexia is almost unknown.  Paulesu had to screen 1200 students for impaired phonological skills in order to identify 18 ‘dyslexic’ students; their reading and non-word decoding skills were markedly superior to the matched English and French dyslexics, and surely many were surprised to be considered ‘dyslexic’.

Wydell and Kondo (2003) reported on an English-Japanese bilingual student who was a superior reader in Japanese and dyslexic in English.  Like Paulesu’s competent Italian dyslexics, he had impaired phonological skills, but seemingly only English was affected.  The authors noted that less than 0.1% of children have a reading disability in Japan.

Said differently, the cure for dyslexia seems to be ‘move to Italy or Germany’.  That’s clearly nonsense.  There is something about the English writing system that makes it troublesome (hint: it has a complex mapping of sounds to spellings).  It is not the writing in our genes.

 

 

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