WEDNESDAY, Sept. 10, 2003 (HealthDayNews) -- The ability to recognize speech patterns isn't something that has to be learned -- it's present at birth.
That's the conclusion of an international study that appears this week in the online edition of the Proceedings of the National Academy of Sciences.
The researchers found that when a newborn baby is exposed to speech sounds, the left hemisphere of the brain becomes active, just as it does in an adult. Yet, if that same infant listens to backwards speech, the left hemisphere largely ignores the input.
"The ability to learn language, namely grammatical systems, is a specialization that is part of the endowment of the human mind," says study author Jacques Mehler, a professor of cognitive neurosciences at the International School for Advanced Studies in Trieste, Italy. Researchers from Japan and France were also involved in this study.
"Our study shows that prior to any contact with language, the brain of the neonate responds specifically to utterances of language, compared to very similar stimuli [backward speech]," Mehler says.
David Salsberg, a pediatric psychologist at New York University Medical Center's Neonatal Intensive Care Unit, says he was surprised at how sophisticated the babies' language skills were at birth.
"These babies were not just responding randomly to sound," he says. "The fact that the babies responded to normal speech and didn't respond to nonsense speech or silence shows that they really are wired to listen for language."
For this study, Mehler and his colleagues used a technique called optical topography to measure blood flow to the brain. Optical topography is a non-invasive imaging technique that uses infrared light to measure the amount of blood flow to certain areas of the brain. An increase in blood flow indicates increased activity in that part of the brain.
The researchers measured blood flow in 14 infants while they heard recordings from two different Italian mothers. The babies weren't offspring of the women. The mothers read children's stories in a normal voice that an adult might use when speaking to an infant.
All of the babies were asleep when they heard the recording. They were between two and five days old.
Blood flow was measured when the babies listened to the recordings played normally, played backwards and during periods of silence. The order in which they listened to each sound-type was randomized.
Blood flow to the left hemisphere increased in all of the babies when they listened to the normal recording of language, suggesting the left hemisphere is dominant in processing speech in infants, just as it is in adults.
When exposed to silence or backwards speech, the babies didn't show similar changes in blood flow patterns.
"The wiring is there," Salsberg says. And, he adds, this study shows babies are "ready for language from the second they're born."
Mehler says that as researchers gain a better understanding of how language is learned, they may be better able to develop therapies for neurological impairments that affect language skills.
More information
To learn more about infants' speech and language development, visit the National Institute on Deafness and Other Communication Disorders or the American Speech-Language-Hearing Association.
