ROBERT SIEGEL, Host:
NPR's Jon Hamilton reports on new evidence that it happens well before children utter their first words.
JON HAMILTON: To figure this out, a team of researchers studied 32 infants. Half the babies were just 4 months old; the rest were 7 months old. The researchers had all of them listen to some common sounds.
(SOUNDBITE OF CHICKENS AND BELLS)
HAMILTON: And also some human voices.
(SOUNDBITE OF NONSENSICAL UTTERANCES AND FOREIGN LANGUAGE SPOKEN)
HAMILTON: Tobias Grossmann, of the University of London, says in infants who were 4 months old, this area did not distinguish between the human and non-human sounds.
D: The striking finding that was that at the age of 7 months, already they show brain responses that indicate that they process human voice very distinctly from other kinds of sounds.
HAMILTON: Then the researchers did a second experiment with the 7-month-old kids. They played them an unfamiliar word spoken with a happy intonation.
U: (Foreign language spoken)
HAMILTON: And the same words spoken in an angry way.
U: (Foreign language spoken)
HAMILTON: But most young kids are just too squirmy to lie still for a scan, so researchers had to wait for a new technology that measures brain activity using beams of light. Grossmann says now, babies just wear a special helmet.
D: The infant can, in fact, be seated on the parent's lap while listening to different kinds of sounds.
HAMILTON: But sometimes, things don't happen that way. And Rhea Paul, of the Yale Child Studies Center, says the new technique for measuring brain responses might help identify very young children with developmental disorders, including autism.
D: One thing we know about children with autism is that they are almost universally delayed in their development of language.
HAMILTON: Paul says the brain areas that respond to intonation may be especially important to watch because children with autism often lack this ability. She says her lab found that toddlers with typical brains paid attention to which syllable in a word was being stressed, and to the rhythm of sentences.
D: Our children with autism, on the other hand, paid attention to neither of those things.
HAMILTON: Jon Hamilton, NPR News.
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