BABY talk sounds silly, but it makes sense to babies. The reason? It鈥檚 easier
to understand than normal English鈥攁t least to the ears of a new
speech-recognition software system.
Patricia Kuhl and her team at the University of Washington in
Seattle鈥攚ho invented the system鈥攈ad already studied the carefully
articulated vowel sounds adults use to talk to babies and toddlers. They found
that these baby-talk vowels are not just spoken more clearly but are
phonetically different to their adult equivalents. People seem to speak in this
way whatever their language, so the researchers wondered if baby talk helps
children to learn to speak.
But they could not test the idea directly. 鈥淵ou can鈥檛 do the experiment
because you would need to take one group of children and prevent them being
exposed to infant-directed speech,鈥� says Bart de Boer, a researcher in Kuhl鈥檚
group.
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So de Boer has simulated the experiment by writing a simple computer program
that picks out key vowels in English. He chose 鈥渙鈥�, 鈥渙o鈥� and 鈥渆e鈥� because the
sounds are very distinctive.
De Boer played the computer recordings of 10 mothers saying the words 鈥渟ock鈥�,
鈥渟hoe鈥� and 鈥渟heep鈥� in two different ways. In one set, the mothers were talking
to another adult, while in the other they were talking to their babies.
The computer鈥檚 task was to distinguish between the three vowel sounds. After
analysing about 200 infant-directed words, the computer could easily tell the
sounds apart. But when it listened to the same number of recordings of the words
as spoken to adults, it recognised only 鈥渆e鈥� correctly.
De Boer does not claim that his program learns in the same way as a child.
But he says that, like the computer, babies probably understand baby talk better
than grown-up speech because of its more distinct vowels.
He hopes his program could also help computer language systems recognise
different dialects. But Deb Roy, of MIT鈥檚 Media Lab in Cambridge, Massachusetts,
is not so sure. 鈥淭his is really telling you more about what adults are doing in
talking to their infants than telling you how to build a computer system,鈥� he
says.