Monday, 15 Sep, 2008 Science

Deaf People Can Feel Their Speech, Scientists Say


When we talk we want to make sure the movement of our mouth is right and our speech sounds correctly. Thus we are able not only to make our speech sound right, but also we make it feel right.

Researchers asked five volunteers who lost their hearing to talk while a robot pushed slightly their jaws. It turned out that the participants learned rather quickly to correct the robotic arm.

"One of the real mysteries of human language is that people who become deaf as adults remain capable of producing intelligible speech for years in the complete absence of any auditory input," said David Ostry, who works as a neuroscientist at McGill University in Montreal, Canada. Together with his colleague, Sazzad Nasir, Ostry headed the research.

The majority of neuroscientists, who make their research on speech, try to focus on the way the human brain learns from different sounds to correct for errors. Ostry mentioned that people feel when they speak right or wrong.

In order to part this ability from learning by hearing, the two scientists sought help of five people with weak hearing who wore cochlear implants. The volunteers were asked to repeat such short words as "sass" and "sane" with their devices turned off. The words were flashed on a computer screen. Simultaneously a robotic arm nudged their jaw, moving it a couple of millimeters. The robot was also able to estimate how much a person pushed back. The arm worked gently so it won't affect the subject's speech.

Scientists saw that after several hundreds of words, the participants corrected the robotic arm by moving their jaw a couple of millimeters thus opposing the robot's gentle push. The same correction the subjects made with their implants turned on.

"When you talk you want to get movement right perhaps as much as you want the speech to sound properly. It's not only making it sound right, it's making it feel right," said one of the scientists.

According to Jeffery Jones, a cognitive neuroscientist at Wilfrid Laurier University in Waterloo, Canada, in order to speak correctly people with weak hearing rely completely on sensing their muscle motions. However, he mentioned that people listen differently to their bodies, depending on the situation.

"If I'm in a very noisy environment such as a dance bar, I'm not going to hear myself very well, so I'm going to rely on another form of feedback," said the neuroscientist.

Source: Newscientist

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