Aug. 5, 2011 at 5:52 PM ET
Recognizing written words is tough enough for people with dyslexia. But a new study suggests the disorder might also make it harder to recognize the voices of people as they speak.
Although dyslexia is regarded as a reading disability, it might be more accurate to think of it as a language disability, the authors say.
People with dyslexia are thought to have difficulty connecting the sound of words with their meaning, so the MIT researchers theorized that their ability to identify speakers’ voices might be impaired. After all, one key component of distinguishing speakers’ voices is how they pronounce words.
To test that hypothesis, they recruited college students with and without dyslexia whose hearing was fine.
The researchers tested their ability to recognize speakers in their native English and in a completely foreign language, Chinese.
“People have shown before that you do better at recognizing voices in a language you know than in a language you don’t know,” says senior author John Gabrieli, a neuroscientist.
If you don’t have dyslexia, that is.
In each language, participants first learned to associate five talkers’ voices with unique cartoon avatars and then were tested on their ability to identify those voices.
So as not to provide any clues that would increase participants’ chances of correctly matching the avatars to the voices, all of the speakers were young men without obvious accents.
When asked to identify the English-speakers, Gabrieli and his coauthors reported July 29 in Science, the people with dyslexia were wrong half the time—much worse than the people who weren’t dyslexic, who missed only 30 percent.
Chinese was another matter. Study participants with dyslexia performed just as poorly when trying to identify the Chinese-speakers as they did with the English-speakers. But this time, the people who weren’t dyslexic missed as many as those with dyslexia. They couldn’t recognize any words, so they couldn’t identify the Chinese speakers on the basis of their pronunciation.
The dyslexic student’s impaired ability to recognize voices was interesting but didn’t present a big problem in their daily lives, Gabrieli says. Oh, sure, he talked to a dyslexic BBC reporter who liked to listen to radio serials and got frustrated trying to figure out which character was speaking. But the woman is a BBC reporter, so she’s not doing too badly.
This line of research could lead to detecting dyslexia in children before they even know how to read, Gabrieli says, noting “there is evidence that early intervention is much more effective than later intervention.”
He and his coathors are now using functional MRI imaging to see whether the brains of people with dyslexia look different that the brains of people without it while trying to name that voice.
How are you at recognizing voices? Can you easily place the celebrity voiceover in a commercial or the latest animated feature?