Parentese, the exaggerated, drawn-out form of speech that people use to communicate with babies, apparently is universal and plays a vital role in helping infants to analyze and absorb the phonetic elements of their parents’ language. An international study shows that infants are so good at analyzing this speech that by the age of 20 weeks they are beginning to produce the three vowel sounds common to all human languages — “ee,” “ah” and “uu.”
“Parentese has a melody to it. And inside this melody is a tutorial for the baby that contains exceptionally well-formed versions of the building blocks of language,” explains Patricia Kuhl, a University of Washington neuroscientist. Kuhl recently headed a team of nine researchers from the United States, Russia and Sweden investigating how infants master the complex task of acquiring speech. Their findings are being published in tomorrow’s issue (Aug. 1) of the journal Science.
The new study examined differences in how American, Russian and Swedish mothers speak to their infants and to other adults. The study shows that parentese is characterized by over- articulation that exaggerates the sounds contained in words. Mothers in the study were, in effect, sounding out “super-vowels” to help their infants learn the phonetic elements of language, says Kuhl, who is the chair of speech and hearing sciences and the William P. and Ruth Gerberding professor at the UW.
“In normal, everyday speech adults generally race along at a very fast pace,” Kuhl says. “But we know it is easier to understand a speaker when they stretch out sounds. That’s why we tend to speak more slowly and carefully to increase understanding when we teach in the classroom or talk to strangers. We also do this unconsciously with babies, giving them an improved verbal signal they can capitalize on by slowing down and over articulating.”
. The mothers in the study were not aware of what they were doing, she says, and so parentese was produced unconsciously and automatically. “When women across three different cultures, speaking three different languages, show the same pattern when speaking to their infants, biology is telling us something about it’s necessity and value to their babies. It’s our job to figure out why they do it and what it’s good for,” Kuhl adds.
To explore differences in the way people communicate with infants and adults, 10 women from each of the three countries were first recorded talking for 20 minutes to their infants, ranging in age from two to five months. Then they were recorded in conversation with an adult.
In both cases, the mothers were told to talk naturally and were given a small list of target words containing the three common vowel sounds and asked to include them in the conversations.. The selected English words were “bead” for the “ee” sound, “pot” for “ah” and “boot” for “uu.” Similar common words were selected in Russian and Swedish. The three languages were chosen because they represent substantially different vowel systems occurring in human languages: Russian has five vowels, English has nine vowels and Swedish has16.
The more than 2,300 recorded target words spoken by the subjects were then isolated and acoustically analyzed by spectrograph. This analysis showed speech directed at infants had more extreme or stretched out vowel sounds than speech with an adult. This was true among all 30 mothers across the three languages, says Kuhl.
The use of parentese seems to benefit infants in three ways, she believes. It makes the sounds of vowels more distinct from one another, and it produces expanded vowel sounds not produced in ordinary adult conversations. This exaggerated speech allows mothers to produce a greater variety of vowel pronunciations without overlapping other vowels.
To speak, an infant must be able to reproduce the appropriate features of individual phonetic elements using a tiny vocal tract which is about only one-quarter the size and lacks the same frequency range of an adult’s. The exaggeration of parentese helps the infant separate sounds into contrasting categories and helps the baby distinguish between different categories, she believes.
“What infants are doing with this information is not memorization. Their minds are not working like a tape recorder,” says Kuhl. “Because their mouths and vocal tracts can’t form the same sounds as adults, they have to transform adult sounds to frequencies they can use. So they must be analyzing speech.”
Babies’ brains, like their bodies, need to be nourished, she says, and parentese provides them with “essential nuggets” of information about language that their lightning fast brains analyze and absorb.
The use of parentese seems to be universal, she says, and parents don’t have to worry about learning it when they take a newborn home from the hospital.
“Moms, dads, caretakers, younger siblings and even college students who were handed a baby in the classroom have been observed speaking parentese. Talking that way seems to be a natural communications mode we all use. That means parents don’t have to work hard at this. Just by talking and communicating with their infants they are playing a vital role without being aware of it,” Kuhl says.
Collaborating researchers in the study come from the Early Intervention Institute in St. Petersburg, Russia, and Stockholm University in Sweden. The research was funded by grants from the National Institutes of Health, the Social Sciences and Humanities Research Council of Canada and the Bank of Sweden Tercentenary Foundation.
For more information, visit the Speech and Hearing Sciences web site at http://weber.u.washington.edu/~sphsc <!—at end of each paragraph insert