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http://hosted.ap.org/dynamic/stories/U/US_MED_HEALTHBEAT_DYSLEXIA?SITE=AP&SECTION=HOME&TEMPLATE=DEFAULT&CTIME=2011-08-01-14-19-05



Aug 2, 12:39 AM EDT



Recognizing voices harder for people with dyslexia



By LAURAN NEERGAARD
AP Medical Writer


WASHINGTON (AP) -- Pick up the phone and hear, "Hey, what's up?" Chances are, those few words are enough to recognize who's speaking - perhaps unless you have dyslexia.

In a surprise discovery, researchers found adults with that reading disorder also have a hard time recognizing voices.

The work isn't just a curiosity. It fits with research to uncover the building blocks of literacy and how they can go wrong. The eventual goal: To spot at-risk youngsters even before they open "Go, Dog, Go!" in kindergarten - instead of diagnosing dyslexia in a struggling second-grader.

"Everybody is interested in understanding the root cause of dyslexia, so we can intervene early and do something about it," says Massachusetts Institute of Technology cognitive neuroscientist John Gabrieli, senior author of the study published last week in the journal Science.

Dyslexia is thought to affect 8 percent to 15 percent of Americans, who can have great difficulty reading and writing. It's not a problem with intelligence or vision. Instead, it's language-based. The brain struggles with what's called "phonological processing" - being able to distinguish and manipulate sounds, like "bah" and "pah," that eventually have to be linked to written letters and words.

A graduate student in Gabrieli's lab wondered if dyslexia would impair voice recognition as well. After all, subtle differences in pronunciation help distinguish people.

How to test that? Previous studies have shown it's easier to recognize voices if they're speaking your own language. So the researchers recruited English-speaking college students and young adults, half with dyslexia, half without. They watched animated characters - like a clown, a mechanic, a soccer player - speaking either English or Chinese, to get familiar with how they sounded.

Then came the test, to match a voice to its character. The volunteers correctly identified the Chinese speakers only about half the time, regardless of whether they had dyslexia. But when they heard English speakers, people with dyslexia still were right only half the time - while the non-dyslexics did far better, identifying 70 percent of the voices correctly.

That provides further evidence of dyslexia's strong link to phonological impairment.

Perhaps more importantly, it's a cleverly designed project that begs the question of whether voice recognition is a problem in young children, too, says Florida State University psychology professor Richard Wagner, who studies how to identify dyslexia early.

Gabrieli says he plans to test 5-year-olds.

Today, researchers know that children who are more phonologically aware when they enter kindergarten have a better shot at easy reading. One way to check that: See how they're able to delete sounds from words - ask them to quickly say "cowboy" without the "boy." Wagner says a child who answers such tasks correctly probably is developing fine. One who fails doesn't necessarily have problems but merely could have misunderstood or not wanted to play along. He says more clear-cut methods are needed.

Differences in brain-processing show up even in infants, says Patricia Kuhl of the University of Washington, who studies how babies learn language.

A colleague in her lab tested how well babies could distinguish "ah" and "ee" sounds between ages 7 months and 11 months of age. Those who did best wound up with bigger vocabularies and better pre-reading skills, such as rhyming, by their fifth birthdays. That doesn't mean they'll go on to experience dyslexia, but it does show how very early development can play a role in reading-readiness.

But Kuhl says the voice-recognition study has broader implications for brain science. It shows that for split-second recognition, the brain's social-oriented right side works together with the speech-perception region of the left brain. People with dyslexia apparently are missing out on some of that interaction.

That interaction, too, begins to appear early. At age 7 months, babies listening to recordings of their native language can recognize if there's a change in speakers, but they miss that speaker change if they're listening to a foreign language, she says. Scientists now have to figure out that neural wiring to learn how it goes awry.

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http://web.mit.edu/newsoffice/2011/voice-recognition-0729.html


Study finds that for people with dyslexia, it’s much harder to identify who is speaking.


Anne Trafton, MIT News Office


July 29, 2011


Distinguishing between other people's voices may seem like a trivial task. However, if those people are speaking a language you don't understand, it becomes much harder. That's because you rely on individuals' differences in pronunciation to help identify them. If you don't understand the words they are saying, you don't pick up on those differences.

That ability to process the relationship between sounds and their meanings, also known as phonology, is believed to be impaired in people with dyslexia. Therefore, neuroscientists at MIT theorized that people with dyslexia would find it much more difficult to identify speakers of their native language than non-dyslexic people.

In a study appearing in Science on July 29, the researchers found just that. People with dyslexia had a much harder time recognizing voices than non-dyslexics. In fact, they fared just as poorly as they (and non-dyslexics) did when listening to speakers of a foreign language.

The finding bolsters the theory that impaired phonology processing is a critical aspect of dyslexia, and sheds light on how human voice recognition differs from that of other animals, says John Gabrieli, MIT's Grover Hermann Professor of Health Sciences and Technology and Cognitive Neuroscience and senior author of the Science paper.

"Recognizing one person from another, in humans, seems to be very dependent on human language capability," says Gabrieli, who is part of MIT's Department of Brain and Cognitive Sciences and also a principal investigator at the McGovern Institute for Brain Research.


Verbal cues


The lead author of the study, MIT graduate student Tyler Perrachione, earned his undergraduate and master's degrees at Northwestern University, where he was involved in studies showing that it is easier to recognize voices of people speaking your own language.

"Everybody's speech is a little bit different, and that's a big cue to who you are," he says. "When you're listening to somebody talk, it's not just properties of their vocal cords or how sound resonates in their oral cavity that distinguishes them, but also the way they pronounce the words."

After Perrachione arrived at MIT, he and Gabrieli decided to try to link this research with evidence showing that phonological processing is impaired in people with dyslexia. They tested subjects in identifying people speaking their native language (English), then Chinese.

When listening to English, the non-dyslexic subjects were correct nearly 70 percent of the time, but performed at only 50 percent when trying to distinguish Chinese speakers. Dyslexic individuals performed at 50 percent for both English and Chinese speakers.

"It's a beautiful study, in the sense that it's so simple," says Shirley Fecteau, a visiting assistant professor at Harvard Medical School and research chair in cognitive neuroplasticity at Laval University in Quebec. "It really seems like a very clear effect on voice recognition in people with dyslexia."

The finding suggests that people with dyslexia may have even more trouble following a speaker than they may realize, Gabrieli says. This adds to the growing evidence that dyslexia is not simply a visual disorder.

"There was a big shift in the 1980s from understanding dyslexia as a visual problem to understanding it as a language problem," Gabrieli says. "Dyslexia may not be one thing. It may be a variety of ways in which you end up struggling to learn to read. But the single best understood one is a weakness in the processing of language sounds."


Friend versus foe


Recognizing other members of one's species by their voices is critical for humans and other social animals. "You want to know who is a friend and who is a foe, you want to know who your partner is," Perrachione says. "If you're cooperating with someone for food, you want to know who that person is."

However, it appears that humans and animals perform that task in different ways. Animals can identify other members of their own species by the sounds they make, but that ability is innate and based on the sounds themselves, rather than the meaning of those sounds.

"We notice individual differences in this learned feature of our communication, which is the words that we use, and that's what really distinguishes human communication from animal communication," Perrachione says.

The researchers believe their work may also offer insight into the performance of computerized voice-recognition systems. Voice-recognition programs with access to dictionary meanings of words might do a better job of understanding different speakers than systems that only identify sounds, Perrachione says.

The researchers are now using functional magnetic resonance imaging (fMRI) to determine which parts of the brain are most active in dyslexics and non-dyslexics as they try to identify voices.