For those who don’t know, dyslexia is actually a general term for a group of disorders “that involve difficulty in learning to read or interpret words, letters, and other symbols, but that do not affect general intelligence” (New Oxford American Dictionary). Most English-speakers are familiar with how this presents in English, but according to the article, the problem for English dyslexics is phonological. In essence, their brains have trouble “determining and manipulating the sound structure” of spoken language, which in turn affects their ability to map sounds onto written letters that are meant to correspond to spoken phonemes. In other words, English-speaker dyslexia isn’t simply scrambling letters around; it’s actually a disorder of sound assessment and manipulation that manifests itself through reading.
In Chinese, according to the latest research, this kind of phonological disorder coexists with a visuospatial disorder, i.e., the same problems with the processing of sounds exist but in addition there may also be problems processing the visual information that is conveyed in characters properly. How do we know this?
The researchers asked normal and dyslexic Chinese readers to judge the physical size of visual stimuli and found that normal readers performed significantly better than dyslexic readers. Brain scans showed that, compared with normal readers, dyslexics exhibited weaker activation in a portion of the brain known to mediate visuospatial processing. Crucially, Siok said, most Chinese dyslexics with the visuospatial problem also exhibited a phonological processing disorder, as demonstrated by their poor performance in a phonology-related rhyme judgment task, suggesting the coexistence of two disorders.
Apparently, this is something of a revelation, and it “presents a challenge to current theories to explain developmental dyslexia”, according to Li Hai Tan, one of the chief researchers. “Our results strongly indicate the need for a unifying theory of sufficient scope to accommodate the full complexity of the observed dysfunctions and interactions of the brain systems underlying reading impairments.”
Also interesting, and perhaps not surprising given the above, is a bit of Tan’s earlier research:
[Dyslexia] appears in a different region of the brain depending on whether someone is a native English or Chinese speaker.
In dyslexic Chinese children, less grey matter was detected in the area of the brain dedicated to identifying images and shapes. In the English-speaking children, the affected region is more closely associated with converting letters to sounds. The discovery was surprising to the researchers because like other common brain dysfunction, they had expected the problem areas to be the same across the board. It does seem to make logical sense, considering the strikingly different ways the two languages represent meaning. Asked if someone dyslexic in one language would necessarily be dyslexic in another, the lead researcher, Li-Han Tan, expressed doubt because “different genes may be involved in Chinese and English dyslexic readers.”
Fascinating, no? Moving for a moment to questions somewhat more fantastic, if the world develops as Joss Whedon predicts and English and Chinese become languages most people can speak both of fluently, can we look forward to a dyslexia-free future? Perhaps. Only one way to find out…
(Note: I can’t find a post on it but I’m sure Sinosplice has already done this, what with Mr. Pasden being a fancy linguist and all. If not, well then, consider yourself scooped, Mr. Pasden. You know, scooped by Harper’s Magazine. Pretty sure there’s no shame in that.)