Better baby communication:

Has natural selection wired your brain for baby talk?

© 2008 -2014 Gwen Dewar, Ph.D., all rights reserved

Baby communication happens along several channels, including those of sight and touch.

But perhaps the most obvious way that parents communicate with their infants is by talking to them.

Call it “baby talk,” “motherese,” or “infant-directed speech” (IDS), this style of speaking isn’t about repeating nonsense words or imitating the baby’s attempts to talk.

It’s about using the same words we use in regular speech, but with distinctive modifications that make the message more clear.

Indeed, this special form of baby communication may be designed to

• get the baby’s attention

• convey clear emotional signals

• help the baby to learn spoken language

There’s even evidence that even adults learn a language more easily from people speaking in "motherese."

How baby communication reshapes the way we talk

It seems to happen automatically. When parents address their babies, they may use the same words that they use to address other adults. But they adopt a special style of speech (Kemler-Nelson et al 1989; Swanson and Leonard 1994; Fernald 2000; Christia and Siedl 2013; Saint-Georges et al 2003):

• Their voices become higher-pitched

• They use a wider pitch range (i.e., more distance between the highest- and lowest-pitched sounds)

• They exaggerate their emotional tone

• They speak in simpler, shorter utterances

• They use greater repetition

• They speak more slowly

• They give special emphasis to words by speaking them in isolation (“Ball!”)

• And, if they are English-speakers, they may also exaggerate the articulation of certain vowel sounds and position target words at the end of a sentence (“Look at the BALL!”)

Moms do it. Dads do it. Kids do it. People lacking experience with babies do it (Fernald et al 1989; Jacobson et al 1983).

What’s more, babies--even newborn babies--prefer to be addressed this way.

In one 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.


A universal mode of baby communication?

Baby talk has been documented in wide range of languages, including languages indigenous to

• Africa and the Middle East (Arabic and Xhosa, a Bantu click language),

• The Americas (Comanche)

• Australia (Warlpiri)

• East Asia (Cantonese, Mandarin, Korean, Japanese, and Gilyak, a Siberian language)

• South Asia (Bengali, Hindi, Marathi, and Sinhala, a Sri Lankan language)

• Europe (English, French, German, Italian, Latvian, and Swedish)

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)

So is baby talk a human universal? It depends on how you define “universal.” Infant-directed speech isn’t practiced everywhere. 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 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 learn language, forge stronger emotional attachments, and develop better social skills.

It’s an intriguing view--especially if you consider these findings.


Baby talk is an attention-grabber

Experimental research has shown that babies’ brains pay more attention to infant-directed speech—-even in their sleep.

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).

And high-pitched vocalizations are used as attention-getters among a variety of species. For example, macaques use high-pitched calls to get the attention of other group members (Koda and Masataka 2003).

There is also evidence that human mothers modulate their pitch according to their babies' levels of attentiveness. In a Japanese study, mothers spoke with lower-pitched voices when their babies were vocally responsive (Niwano and Sugai 2003). But when babies were more reticent, moms raised the pitch.

Infant-directed speech might command attention for other reasons, too, such as the greater pitch range and more exaggerated emotional tone.

This seems possible because

• babies like it when men use infant-directed speech, even though male voices don’t reach the same heights of pitch than women’s voices do (Werker and McLeod 1989),

• babies like to listen to adult-directed speech when it is highly-charged with pleasant emotion (Singh et al 2002), and

• when adult-directed speech is highly emotional, it takes on many of the characteristics of baby communication. This includes a higher pitch, but it also includes a greater pitch range and slower tempo (Trainor et al 2000).


Baby talk makes emotions—and intentions—more obvious

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.

The results?

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).


Is baby talk designed to help babies learn speech?

We’ve seen how infant-directed speech might help babies pay closer attention. It might also help babies “read” the emotions and intentions of others.

But what about learning to speak?

Experiments suggest that infant-directed speech helps infants develop several key speech perception skills, including

• the ability to discriminate between different speech sounds

• the ability to detect the boundaries between words in a stream of speech

• the ability to recognize distinct clauses in a stream of speech

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 more details, see this article about language learning, baby communication, and infant-directed speech.

Other forms of baby communication

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.



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Photo credits for "Baby Communication":

image of father and baby ©iStockphoto.com/daniel rodriguez

image of Indian family by Ken Hammond

image mother & infant ©iStockphoto.com/Rohit Seth


Content of "Baby Communication" last modified 2/14