Baby communication operates on multiple sensory channels, including sight and touch.
But of course human beings are linguistic creatures, so we expect our infants to learn language. How does this happen?
You might argue that our babies deserve all the credit.
However you look at it, it's an amazing feat. Without textbooks or dictionaries or explicit instruction, babies acquire language.
But that doesn't mean that babies work everything out on their own, without any help. If you've ever struggled to understand a new language, you know that not every speaker is equally easy to understand. Some folks, noticing your difficulties, alter their normal speech patterns to make their meanings more obvious. Does the same thing happen for infants?
Enter Exhibit A, the phenomenon that researchers call "infant-directed speech."
Also called "parentese," or "motherese," it's a form of communication that people seem to adopt naturally when they interact with a baby.
Suddenly their vocal pitch goes up. They speak more musically, using a wider pitch range (i.e., more distance between the highest- and lowest-pitched sounds). They change the tonal color, or timbre, of their voices (Piazza et al 2017), and exaggerate their emotional tone (Kemler-Nelson et al 1989; Saint-Georges et al 2003).
They speak more slowly, and use shorter, simpler sentence structure. They tend to repeat themselves a lot, and give certain words emphasis by uttering them in isolation. Instead of saying, "look at the teddy bear," they might call out, "bear!" (Christia and Siedl 2013; Fernald 2000).
They may also exaggerate the articulation of certain vowel sounds and position target words at the end of a sentence. Look at the BALL! (Swanson and Leonard 1994).
Not everyone does it, but it's remarkably common. Mothers do it. Fathers do it. Children do it. People lacking experience with babies do it (Broesch and Bryant 2017; Fernald et al 1989; Jacobson et al 1983).
And this distinctive style of baby communication has been documented in a wide range of languages, including languages indigenous to
For references, see (Das 1989; Dil 1971, Ferguson 1964; Fernald et al 1989; Fernald and O’Neill 1993; Kelkar 1965; Meegaskumbura 1980; Saint-Georges et al 2013; Sulpizio et al 2017)
So is this "baby talk" a human universal?
It depends on how you define "universal." As we've alread noted, infant-directed speech isn't practiced absolutely everywhere by everyone. Parents who are depressed or self-conscious aren't so good at ID speech (e.g., Kaplan et al 2007). And some parents may be discouraged by cultural attitudes.
For instance, anthropologists have reported that the Kaluli of New Guinea don't engage their babies in conversation (Sheiffelin and Ochs 1996). It's also been reported that the Quiché Mayan speak to their babies in the same pitch that they use to address adults (Ratner and Pye 1984).
But these cases are exceptions to the rule. Yes, infant-directed speech is subject to individual differences and cultural influences. But you can say the same thing about most human behavior—including other parenting practices, like breastfeeding.
So some researchers are comfortable characterizing infant-directed speech as a human universal. Indeed, researchers like Anne Fernald and Mary Monnot have argued that baby talk is an evolved, species-specific adaptation (Fernald 1992; Monnot 1998).
According to this idea, infant-directed speech evolved to facilitate baby communication. It's a tutorial style of speech, one designed to help babies develop social skills, forge stronger emotional attachments, and learn language.
It's an intriguing view, especially if you consider these findings.
In a classic experiment, researchers Robin Cooper and Richard Aslin presented 2-day old infants with audio recordings of adult speech.
The babies could control how long each playback lasted by turning their heads toward a loudspeaker.
In some trials, babies heard infant-directed speech. In other trials, they heard adult-directed speech.
Cooper and Aslin found that the newborns turned their heads longer in response to infant-directed speech (Cooper and Aslin 1990).
Similar experiments have been performed on older babies, with the same results. In one study, five-month-old babies showed a preference for strangers who addressed them with infant-directed speech, even after the talking had ended (Schachner and Hannon 2011). But the behavior of newborns seems especially compelling. It suggests that babies are born with an unlearned preference for infant-directed speech.
Experimental research has shown that babies' brains pay more attention to infant-directed speech.
In one study of 3-month old infants, researchers played back recordings of adult voices to sleeping babies. In some trials, babies heard infant-directed speech. In other trials, they heard adult-directed speech. When sleeping babies listened to the baby talk, they experienced an increased blood flow to the frontal area of their brains (Saito et al 2006).
Similarly, cognitive neuroscientists have
measured event-related potentials, or ERPs, in 6- and 13-month old
babies as they listened to both infant-directed and adult-directed
speech. The babies’ brains experienced more electrical activity when
they listened to baby talk (Zaigl and Mills 2007).
Why does baby talk grab the attention?
It might be the higher pitch.
Experiments have shown that infants listen longer to songs when they are sung in a higher pitch (Trainor and Zacharias 1998). There is also evidence that human mothers raise voice pitch when they want to get the attention of a seemingly bored infant (Niwano and Sugai 2003).
And high-pitched vocalizations are used as attention-getters among a variety of species. For example, macaque monkeys use high-pitched calls to get the attention of other group members (Koda and Masataka 2003).
But why should human infants show such this preference? It could be that it's easier for them to pick out high-pitched voices against background noise. Alternatively, babies might perceive high-pitched voices as less aggressive (Kalashnikova et al 2017).
And it might be a byproduct of the infant's interest in his or her own voice. According to this idea, infants are motivated to attend to their own voices because they need to fine-tune the speech sounds they make. As a result, they possess a bias for voices with infant-like characteristics (Massapollo et al 2016).
Infant-directed speech might command attention for other reasons, too, such as the greater range of pitch, and more exaggerated emotional tone.
This seems possible because
Cultures vary widely in the amount of emotion that is conveyed in speech. But within a given culture, infant-directed speech is more demonstrative and emotional.
Does this make the intentions of a baby talker more obvious?
It seems likely. After all, some Americans speak to their pets in a sing-song, emotionally-exaggerated way (Mitchell 2001; Burnam et al 2002). Your dog might not understand the words, but he does understand the tone.
So we shouldn’t be surprised if members of our own species have an easier time interpreting the emotions of infant-directed speech.
In an interesting cross-cultural experiment, researchers played back recordings of American English-speaking mothers to adults of the Shuar, an indigenous South American group that practices hunting and horticulture (Bryant and Barrett 2007).
The Shuar adults could reliably identify which utterances were baby talk. And, despite no knowledge of English, adult listeners were able to classify the speakers’ intentions into four categories--prohibition, approval, comfort, or attention.
They could do this when the English-speaking utterances were adult-directed.
But they performed even better when the utterances were baby talk.
Do babies pick up on the emotional cues of infant-directed speech?
Experiments suggests that they can.
In one study, Stanford University researcher Anne Fernald and colleagues presented 5-month old American babies with speech they had never heard before: Vocalizations of approval and prohibition spoken in German, Italian, and Japanese.
Then researchers noted the babies’ affective responses to each vocalization.
Fernald’s team found that the American babies listened with neutral affect to the Japanese utterances—perhaps because Japanese moms don’t use as wide a pitch range in their infant-directed speech (Fernald et al 1989).
But when it came to the German and Italian utterances, the babies responded with the appropriate emotion to each one-—positively to approvals and negatively to prohibitions.
However, this was true only when the babies had been presented with infant-directed speech. When the messages of approval or prohibition took the form of adult-directed speech, infants did not distinguish between them.
A somewhat similar experiment was performed on Canadian babies listening to utterances in a non-native language. In this case, 4- to 9-month old babies watched a videotape of a woman speaking Cantonese. When the woman's intention was baby communication, infants were more likely to respond with pleasant emotions (Werker et al 1994).
We've seen how infant-directed speech might help babies pay closer
attention. It might also help babies "read" the emotions and intentions
But what about learning to speak?
Experiments suggest that infant-directed speech can help infants develop several key speech perception skills, including
And infant-directed speech may help adults, too.
In experiments conducted by Roberta Golinkoff and Anthony Alioto, English-speaking adults found it easier to learn new Chinese words when the words were spoken in the baby talk register (Golinkoff and Alioto 1995).
Does this imply that infant-directed speech is a kind of "tutorial" mode of baby communication? It seems to. In fact, there is even evidence suggesting that babies learn speech faster when their parents use particularly expressive forms of infant-directed speech.
For example, in families where parents use infant-directed speech, babies who spend more time in one-on-one conversion develop better language skills (Ramírez-Esparza et al 2017).
For more details, see this article about language learning, baby communication, and infant-directed speech.
Speech isn't the only way that parents can talk with babies. As deaf parents know, babies are also receptive to learning sign language. Even babies of hearing parents may benefit from using gestures during speech. For more information, see this article on the science of baby signs.
Furthermore, it isn't merely exposure to words or hand signs that help babies learn. Studies suggest that eye contact plays a crucial role. Read more here.
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Photo credits for "Baby Communication":
title image of mother and infant by Pascal Maramis /flickr
image of woman smiling down on baby by Tim Samoff / flickr no derivatives
image of father and baby ©iStockphoto.com/daniel rodriguez
image of newborn clutching mother by Nick Koch Weiler / flickr
Content of "Baby Communication" last modified 12/17