Speech involves more than just sounds. A speaker must manoeuvre jaw, tongue, vocal cords and associated machinery into the right position. An Article in this week's Nature (Vol. 423, No. 6942, 19 June 2003, pp. 866-869) demonstrates how the brain can control these purely mechanical aspects of speech independent of sound production.
David J. Ostry and colleagues wired up volunteers to a robotic device that applied forces to the jaw when they spoke. In this way, the mechanical component of speech production could be altered, whilst the acoustics remained the same. As subjects repeated words, they corrected their speech movements to compensate for the extraneous jaw movements. This happened regardless of whether or not they spoke out loud.
Because speech doesn't have to have sound involved, it can be regarded as an entirely mechanical process, akin to riding a bicycle. This is a new way of thinking about speech production, the researchers claim. It could also explain how deaf people learn to speak 'naturally' despite never hearing a word that they say.
David J. Ostry
Tel: +1 514 398 6111
(C) Nature press release.
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