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Why are some bilingual people dyslexic in English but not their other language?

Taeko dyslexia 920x540

In the English-speaking world, dyslexia is a learning disorder we’re all familiar with – if we don’t have it ourselves or have a friend or family member that struggles with it, we’re likely to have known someone at school or university who found reading and writing trickier than their peers.

In fact, more than 1 in 10 people that grew up with English as their first language are said to have dyslexia, with wide consensus pointing towards a person’s genetic history as the leading cause. One, it would appear, is either born dyslexic or not.

So, how then have we ended up with the phenomenon that some people who speak both English and another language can be dyslexic in one, but not the other?

The answer, it seems, is hidden in the characteristics of a language and its writing system.

“The English writing system is so irregular – print to sound or sound to print translation is not always one to one,” Brunel University London’s Professor of Cognitive Neuroscience, Prof Taeko Wydell, recently told the BBC radio documentary Dyslexia: Language and childhood.

“This irregularity or inconsistency makes it especially difficult for dyslexic individuals to master reading and writing in English.”

Listen now to the BBC's Documentary Podcast - Dyslexia: Language and Childhood

So, for example, ‘mint,’ ‘lint’ and ‘hint’ – all ‘int’ words – are pronounced differently to the word ‘pint’. And the words ‘through,’ ‘though’ and ‘tough’ all sound different, despite looking on the page like they should sound similar. This makes English a so-called ‘opaque’ language. The only way one knows the individual pronunciations, is to learn and remember each exception, such as ‘pint’ or ‘yacht,’ individually.

“This kind of irregularity doesn’t happen in other languages such as Italian, Spanish or Finnish,” said Prof Wydell, pointing to so-called ‘transparent’ languages where combinations of letters are always pronounced the same, with some rare exceptions. As such, studies have shown Italian speakers are only half as likely to show signs of dyslexia than English speakers.

Levels of dyslexia can also be far lower in countries with a symbol-based writing system, such as Japanese or Chinese, because of how those writing systems are taught in schools.

When children learn to write Japanese Kanji or Chinese characters, they consistently repeat the order of strokes required to draw each character whilst speaking aloud the corresponding word. This helps the motor sequence – the combination of small movements required to write each word or sound – get ‘wired in’ to their brains.

“So, when the child is asked to write later on, the child’s hands almost automatically write down the character from memory,” said Prof Wydell.

It’s therefore possible for people who learn to read and write in Chinese or Japanese to have no idea they have dyslexia until they later begin to learn English and are forced into reading and writing in a totally different way.

So low is the prevalence of diagnosed dyslexia in primary schools in Japan –  as low as 1.4% when writing with syllabic Kana characters and 6.9% when writing with Kanji characters – that it wasn’t until 2006 that Prof Wydell published STRAW-I, the first and only standardised and systematic screening test for identifying dyslexia in Japanese primary school children.

By 2013, nearly 9000 organisations across Japan were using the test, and in 2014 Prof Wydell’s work was awarded 4* ‘world-leading’ status by the UK government’s Research Excellence Framework (REF).

The test has since been extended, with the new standardised test – STRAW-R – now being suitable for children up to 15 years old, significantly increasing the chance that young people in Japan will receive a timely diagnosis for dyslexia and be able to access to the right support throughout their schooling.

 

Reported by:

Tim Pilgrim, Media Relations
+44 (0)1895 268965
tim.pilgrim@brunel.ac.uk