Does my pwecious bab-ee want a dwink-ee? Or her blank-ee? Baby talk's vowel-heavy vocabulary and high pitch are heard in nurseries around the world. But infant-directed speech (aka “motherese” or “parentese”) isn't just child's play—it's a source of fascination for linguists who hope to understand how the lilting babble impacts learning.
Most babies start developing their hearing while still in the womb, prompting some hopeful parents to play classical music to their pregnant bellies. Some research even suggests that infants are listening to adult speech as early as 10 weeks before birth, gathering the basic building blocks of their family's native tongue. Early language exposure seems to have benefits to the brain—for instance, studies suggest that babies raised in bilingual homes are better at learning how to mentally prioritize information.
So how does the sweet if sometimes absurd sound of infant-directed speech influence a baby's burgeoning smarts? Here are some recent studies that explore the science behind baby talk:
Moms Use More Baby Talk, While Dads Keep It Real
Dads don't use baby talk as often or in the same ways as moms—and that's perfectly OK, according to a new study. Mark VanDam of Washington State University at Spokane and colleagues equipped parents with recording devices and speech-recognition software to study the way they interacted with their youngsters during a normal day. This was the first study to focus on the way fathers interact verbally with their young “in the wild” and then analyze those interactions with automatic software. The results were presented on May 18 at the Acoustical Society of America meeting in Pittsburgh.
“We found that moms do exactly what you'd expect and what's been described many times over,” VanDam explains. “But we looked very carefully at dads, and we found that dads aren't doing the same thing. Dads didn't raise their pitch or fundamental frequency when they talked to kids. So whatever they are doing, it's not that stereotypical type of speech.”
Don't get the wrong idea—dads are not somehow failing their kids by avoiding baby talk, he stresses. Their role may be rooted in a theory called the bridge hypothesis, which dates back to 1975. It suggests that dads use less familial language to provide their kids with a bridge to the kind of speech they'll hear in public.
“The idea is that a kid gets to practice a certain kind of speech with mom and another kind of speech with dad, so the kid then has a wider repertoire of kinds of speech to practice," says VanDam. "So it may actually be an expanding role when dad doesn't do the same thing as mom, rather than a restricting role or some type of negligence.”
Baby Talk Boosts Vocabulary
Baby talk may have serious benefits—including a boost in early language learning that becomes more apparent as babies age. Scientists from the University of Washington and the University of Connecticut collected thousands of 30-second conversations between parents and their babies, fitting 26 kids with audio-recording vests that captured language and sound during a typical eight-hour day. The scientists then used analysis software to quantify how much the parents used baby talk during more than 4,000 encounters.
This April 2014 Developmental Science study found that the more baby talk parents used, the more their youngsters began to babble. All that babbling produced some surprising results at older ages. When researchers checked in with the same babies at age two, they found that frequent baby talk had dramatically boosted vocabulary regardless of socioeconomic status. Two-year-olds who had heard the most baby talk knew an average of 433 words, while those whose families had been the quietest knew an average of 169 words.
“Those children who listened to a lot of baby talk were talking more than the babies that listened to more adult talk or standard speech,” says co-author Nairán Ramírez-Esparza at the University of Connecticut. “We also found that it really matters whether you use baby talk in a one-on-one context,” she adds. “That's the combination that really predicts language development most powerfully. Those babies are able to pay more attention to the sounds, and they have an opportunity to talk back. The more parents use baby talk one-on-one, the more babies babble, and the more they babble, the more words they produce later in life.”
Babies Would Rather Listen to Other Babies
In a related vein, another study suggests that parents might want to pair their youngsters up so they can babble more with their own kind. In a March 2015 study in Developmental Science, researchers from McGill University and Université du Québec à Montréal found that babies seem to prefer listening to each other rather than to adults—which may be why baby talk is such a universal tool among parents.
Because babies can't tell us what they're thinking, the team devised a method to determine their preferences. They played repeating vowel sounds made by a special synthesizing device that mimicked sounds made by either an adult woman or another baby. This way, only the impact of the auditory cues was observed. The team then measured how long each type of sound held the infants' attention. They found that the “infant” sounds held babies' attention nearly 40 percent longer. The faux baby noises also induced more reactions in the listening infants, like smiling or lip moving, which approximates sound making. The team theorizes that this attraction to other infant sounds could help launch the learning process that leads to speech.
“It may be some property of the sound that is just drawing their attention," says study co-author Linda Polka of McGill's School of Communication Disorders. “Or maybe they are really interested in that particular type of sound because they are starting to focus on their own ability to make sounds. We are speculating here but it might catch their attention because they recognize it as a sound they could possibly make.” In that case, Polka theorizes, baby talk could be the adults' way of starting to familiarize their young with what their own voices will sound like. “Maybe we are playing right into that by using baby talk,” she notes. “Or maybe we are even shaping it.”
Babies Learn Even From Garbled Speech
Infants begin to build their vocabularies based on the sounds of their native languages. One long-held theory is that mothers try to aid this process by hyperarticulating their words when engaging infants in baby talk. However, a January 2015 study suggests that baby talk is less clear than normal adult-to-adult communication—at least among Japanese moms.
Nearly two dozen Japanese mothers in Tokyo and Paris were recorded during 18 to 24 months of speaking to their children and, as a control, speaking to an adult experimenter. Researchers at Tokyo's RIKEN Brain Science Institute then spent five years sifting through the speech data, noting common syllables and tagging the speech components, from individual consonant and vowel sounds to entire phrases. An automated analysis investigated the acoustic similarities and differences between any two syllables—“po” and “bo”, for example—and applied the results over the 118 most commonly spoken syllable contrasts.
The results, published in Psychological Science, showed that the mothers spoke more clearly to other adults than they did to their own babies. The study didn't determine why mom's baby talk was less clear, although it's possible that moms may direct much of their focus on communicating emotions or simply keeping a child's attention at the expense of clarity. It's also not yet known if speaking clearly helps language learning, the authors noted. Babies seem to adapt well to even the less-clear speech they hear.
“Our results suggest that, at least for learning sound contrasts, the secret to infants’ language-learning genius may be in the infants themselves—the fact that they are able pick up sounds from input that is less clear than that used by adults with each other makes this accomplishment all the more remarkable,” co-author Andrew Martin told the Association for Psychological Science's Observer publication.
This Is Your Brain on Baby Talk
Even if the words are fuzzy, it seems the slow, exaggerated sound of baby talk may make it easier for infant brains to practice early speech sounds and model the needed mouth and motor movements before they speak for the first time.
In a July 2014 study published in Proceedings of the National Academy of Sciences, a total of 57 babies from two slightly different age groups—seven months and eleven and a half months—were played a number of syllables from both their native language (English) and a non-native tongue (Spanish). To track their reactions, the infants were placed in a brain-activation scanner that looks much like the egg-shaped hair dryers once found in beauty salons. Although the babies didn't speak, the equipment recorded brain activity in an auditory region called the superior temporal gyrus and in other areas known to guide the motor movements that produce speech. The results suggest that listening to baby talk prompts infant brains to start practicing their language skills.
"Finding activation in motor areas of the brain when infants are simply listening is significant, because it means the baby brain is engaged in trying to talk back right from the start, and suggests that seven-month-olds' brains are already trying to figure out how to make the right movements that will produce words," co-author Patricia Kuhl, of the University of Washington's Institute for Learning and Brain Sciences, said in a release.
The novel look at baby brains may have also uncovered a process by which babies recognize differences between their native language and other tongues. The seven-month-olds responded to all speech sounds whether in their native English or in the non-native Spanish. But by age 11 or 12 months, the infant brains were working harder at the motor activations of non-native sounds compared to native sounds. Kuhl and colleagues theorize that baby brains at this age may already require more effort to guess and model the movements that produce non-native speech.