Be careful what you say; little ears might be listening.
Experimental psychologists have found that infants seem toremember relatively complex words, even when they only hear thosewords in tape-recorded stories without the benefit of any otherstimuli. Audio-taped children's stories containing words like"peccaries" and "python" were played to 8-month-old infants once aday for 10 days; two weeks later, 36 words that occurred mostfrequently in the stories were played back to the babies in listform.
Perhaps the most remarkable finding was that the babiesrecognized the words, even though they sounded different in listform than they did in the stories.
"When we just read a list, we actually pronounce those wordsa little bit differently; those words have a very differentacoustic form than they had in the stories," said Peter Jusczyk,a professor in the Department of Psychology at The Johns HopkinsUniversity.
But the experiments indicated that the infants rememberedthe words they had heard in the stories, suggesting that babiesmemorize words that occur frequently in speech, an importantprerequisite for learning language.
The findings will be detailed in a paper to be published onSept. 26 in the journal Science.
Although much work has been conducted to investigate howchildren learn the meanings of words, there has been littleresearch aimed at learning how infants focus on the sounds ofwords, said Jusczyk, who co-authored the paper with Elizabeth A.Hohne, a psychologist at AT&T Labs in Holmdel, N.J.
The scientists recorded women narrating three differentchildren's stories, each lasting about 10 minutes. Thenresearchers visited the homes of 15 infants, playing the storiesto them every day for 10 days. In the end, the 8-month-old babieshad heard each story 10 times.
The psychologists identified the 36 content words -- usuallynouns -- that occurred most frequently in the stories. Then theyarranged those words in lists of 12 words each.
Two weeks after the final visit to the infants' homes, thebabies were brought to Jusczyk's lab at Johns Hopkins. One at atime, they were placed inside a special testing booth, where theylistened to the lists containing the words that occurred mostfrequently in the stories. Then they listened to lists of other,similar-sounding words that did not occur in the stories.
A light flashed above the speaker through which the taperecording was played. When the infants looked at the light, theword lists began and continued to play as long as the infantslooked toward the light. Babies who stopped listening to thewords looked away from the light, telling the researchers howlong the infants had listened to specific lists of words.
"What we found was that the babies listened longer to thelists of words from the stories, significantly longer," Jusczyk said.
Previous research using the technique has shown that infantstend to listen longer to words that are more familiar to them. Theresearchers, however, wanted to make sure that the infants were not listeninglonger to the story words simply because they found them moreinteresting, so they brought a new group of infants to the labwho had never heard the stories on tape. When those infants heard the lists ofthe story words and the non-story words, they showed no preference andactually listened slightly longer to the non-story words.
"That showed us that the experience the babies had had athome listening to the stories had an impact on what they reallyremembered," Jusczyk said. He noted that the infants learned the words eventhough they never had any personal contact with the women who narrated thestories.
"So, imagine what happens when you actually have the baby inyour arms, and you are reading the story and you are turning thepages of the book," he said. "You'd expect that they would beeven more inclined to store some of that information."
The babies who had never heard the stories listened anaverage of about six seconds to the story words and slightly morethan that for the non-story words. The infants who had heard thestories listened an average of less than six seconds to thenon-story words but nearly seven seconds to the story words.
"A second doesn't sound like a lot of time, but it'sconsistent," Jusczyk said. "The whole object of this was to seewhether, when infants are listening to people talk or listeningto people read stories to them, they are storing any informationaway about sound patterns that occur frequently."
Ultimately, scientists are trying to learn how youngchildren are able to learn and master the complexities oflanguage, a difficult task for the adult brain and the mostpowerful computers.
At about 18 months, a child's vocabulary and grasp oflanguage suddenly expand, and scientists don't know why. Onepossible explanation is that children may begin storing thesounds and meanings of words while they are infants, and suddenlythey are able to connect the words with meanings.
"It's sort of like working on a puzzle. You get a few piecesand then everything falls into place," Jusczyk said.
Learning words requires storing both sounds and meanings.This study shows that infants sometimes store the sounds ofwords, even when they have not yet learned the meanings, he said.
This research was supported by the National Institute of Child Health andHuman Development of the National Institutes of Health.
More information on Jusczyk and his research is available from his WorldWide Web page at http://www.psy.jhu.edu/~jusczyk
EMBARGOED FOR RELEASE AT 4 P.M. EDT ON THURSDAY, SEPT. 25, 1997
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