How “Baby-talk” Words Support Language Development

By Julie Erdmann Speech-Language Pathologist & Clinical Program Assistant, The Hanen Centre

If you were to walk past a parent talking to her baby, you might hear any of the following phrases:

“Uh oh!”


“Where’s your belly?”

“Woof-woof says the dog!”

“Night-night, baby!”

As Hanen certified SLPs, we know that modeling playful words is a natural part of interaction-building activities. In It Takes Two to Talk®, we teach caregivers to use this type of vocabulary when they join in and play in order to follow their child’s lead and let the interaction grow. “Fun sounds and words are easy to remember and understand because they’re said with lots of animation and often have gestures that go with them” (Weitzman, 2017, p. 37) These words are a familiar part of parentese, or infant directed speech.

Infant directed speech (IDS) consists of language that is, as its name suggests, directed specifically to the child and not conversation that he may simply overhear. IDS has been studied since the 1960s (Ferguson, 1964) and the research on this topic has continued. Studies have shown that “[i]nfant directed speech…systematically differs from adult directed speech” (Ota, Davies-Jenkins, Skarabella, 2018). Some studies have focused on the quantitative variation between IDS and adult-directed speech (ADS), showing that all the elements are the same but vary by degree. Infant directed speech (IDS) generally has slower speech rates, higher pitch ranges, and longer pauses than speech directed at adults. Sentences are shorter than those in adult directed speech (ADS) and contain more concrete and less diverse vocabulary – the same set of words tend to be used more often (Cristia, 2013; Phillips, 1973; Saint-Georges, Chetouani, Cassel, Apicella, Mahdhauoi, Muratori, Laznik, & Cohen, 2013; Thiessen, Hill, & Saffran, 2005; Trainor, L. J., Austin, C. M,. & Desjardins, R. N., 2000). But lately the focus has shifted to the qualitative differences between ADS and IDS. It turns out that what we say, and not just how we say it, promotes accelerated vocabulary growth.

We now have evidence that the kinds of words we use in IDS, like the ones at the beginning of this article, not only facilitate first word development, but also allow children to gain vocabulary more quickly as they get older. There are three specific word types that we only use in IDS, and not in ADS. These words feature iconicity, diminutives, and reduplications. These words are referred to as baby-talk words. Let’s take a closer look at each type of baby-talk word.

1. Iconic words

Iconicity is a relationship of resemblance or similarity between the two aspects of a sign: its form and its meaning. An iconic sign is one whose form resembles its meaning in some way. These words provide a clear referent to the object or action they label; onomatopoeia is a frequently used type of iconicity.

· Choo-choo helps the child match the sound to the vehicle that produces it.

· In American Sign Language, the sign for eat mimics bringing food to the lips.

Iconicity is important because understanding that specific sound combinations or gestures represent specific things is a prerequisite for word learning. When a child hears the word "choo-choo", he can more easily deduce that it refers to the train making that same noise and not the tracks, the trees, the sky, or the clouds. Once babies discover the connection between a symbol and its action or item, they can apply this knowledge to new words.

2. Diminutives

These words follow consistent grammatical rules, helping babies learn predictable word endings along with the rhythm and intonation of their language. Diminutives facilitate word learning in 2 ways:

a) Diminutives have very limited word endings. For example, in English they always end in “-y”:

doggy, kitty, tummy

In Spanish they end in “-ito” or “-ita” depending on the gender of the word:

agua to aguita (water to a bit of water), carro to carrito (car to little car)

b) They have clear syllable stress patterns. For example, in English, diminutives always follow the same two-syllable CVCV pattern, e.g. cat to kitty, dog to doggy, stomach to tummy. The first syllable is always stressed: kitty, puppy, tummy.

In Spanish, the diminutive places stress on the penultimate syllable; e.g. agua to aguita, manzana to manzanita (apple to little apple or a bit of apple). This is true even for words that have a different syllable stress pattern in their original form: telefono to telefonito (telephone to little telephone).

These two features of diminutives provide cues for word segmentation as babies use the syllable stress patterns as a template for deciding what might be a word. They also search for fixed word endings, like “-y” in English, which helps them identify word boundaries.

3. Reduplicatives

These words are physically easier for babies to say and thus easier for them to recognize (Endress, Nespor, & Mehler, 2009; Gervain, Berent, & Werker, 2012). This also likely allows these words to be committed to memory more easily (Ota, Davies-Jenkins, & Skarabela, 2018).

· Using the same example as in iconic words, choo-choo is simpler to say than train/tren in English, French, or Spanish.

· Bow-wow, guau-guau, and wan-wan are simpler than dog in English, perro in Spanish, and inu in Japanese.

Reduplicatives come in multiple forms, all of which were analyzed in the study. Examples include:

· full (night-night)

· partial with same initial consonant (daddy)

· partial with rhyming pattern teeny-weeny)

Reduplicatives lead to word learning because the repetition helps with word segmentation, making the words stand out in running speech, which leads to their being easier identify and remember.

A standard lexicon of up to 60 baby-talk words is found in nearly every well-documented language, both spoken and signed (Ferguson, 1964; Skarabela, Ota, Fazekas, & Wihlborg, 2015). There have been numerous studies examining the benefits of baby-talk features at the level of acquiring first words (Imai, Miyazaki, Yeung, Kantartzis, Okada, & Kita, 2015; Perniss, Lu, Morgan, & Vigliocco, 2018; Skarabela, Ota, Fazekas, & Wihlborg, 2015).

However, Mitsuhiko Ota and his colleagues at the University of Edinburgh believed that the value of baby-talk words goes beyond helping infants learn first words. In their research they posited that “[i]nfants who receive lexical input with a higher incidence of these features should have a faster overall rate of lexical growth at the initial stage of vocabulary development” (Ota et al, 2018). In other words, they set out to discover if the use of baby-talk words not only facilitated early word learning, but also accelerated future vocabulary acquisition.

They released the results of their study in a paper entitled “Why Choo-Choo Is Better Than Train: The Role of Register-Specific Words in Early Vocabulary Growth” (2018).

The Study

Ota and colleagues tracked the vocabulary size of 47 English-learning infants from 9 to 21 months in a largely middle-class urban community in Scotland. The participants included 23 boys and 24 girls whose primary home language was English. The children were born at full term and had no known hearing issues. The researchers measured the number of times adults or older siblings used baby-talk words when speaking directly to the children at 9 months of age.


“If the hypothesis that baby-talk words can facilitate general lexical development is correct, then we expect individuals who receive more lexical input matching the characteristics of baby-talk words to show some advantages in vocabulary growth.” (Ota et al, 2018)

In other words, they predicted that the characteristics of baby-talk words would speed up word learning during the early stages of language development.


When the children were 9 months old, families digitally recorded at least 15 minutes of verbal interactions during daily routines (most frequently meal time, free play, bath time, bed time)Once a total of 90 minutes of interactions were captured, the researchers collected and transcribed 60 minutes’ worth of the recordingsParents tracked vocabulary development with the UK version of the MacArthur/Bates Communicative Development Inventory (CDI) at 9 months, 15 months, 21 months


Ota et al measured the number of times family members used the following types of words when speaking directly to the 9-month-old child; i.e. child-directed lexical input:

Iconicity (woof, choo-choo, bang)Diminutivization (doggy, kitty, mommy) They also included non-diminutives that followed the same structural rules: 2 syllables, second one ending in “-y” (baby, soggy, cookie)Reduplication: full (night-night), partial with same initial consonant (daddy) or rhyme (teeny-weeny)Combination of iconicity and reduplication (quack-quack, tick-tock)Combination of diminutivization and reduplication (mummy, baby, cookie)

Data Analysis

The researchers first analyzed vocabulary growth on the children’s complete word inventories from the CDI. Given that the hypothesis was “that the effects of IDS-specific lexical features in the input should extend beyond the acquisition of the very words that have those features and apply indirectly to other words”, the researchers also ran an analysis on the CDI results excluding iconicity, diminutives, and reduplicatives.


Although not the focus of their hypothesis, Ota et al found that a higher level of maternal education was associated with accelerated growth of vocabulary. This is consistent with prior research showing that mothers with higher levels of education interacted more frequently with their children, leading to larger child vocabularies by age 3 (Hart & Risley, 1995). However, diminutives and reduplicated words contributed to vocabulary growth independent of maternal education. Specifically:

Use of diminutives and reduplicated words with infants promoted vocabulary growth beyond words with the same features, as measured at 21 months. For every 1% increase in caregiver use of diminutives, babies’ vocabulary grew by 3.17 words per monthFor every 1% increase in caregiver use of reduplicated words, babies’ vocabulary grew by 2.72 words per month.Only about 5% of speech addressed to infants contained diminutive or reduplicative structures—this small section of linguistic input was shown to have a large effect on early language developmentSurprisingly, the use of iconicity had no effect on lexical growth in this study

Ota and his colleagues concluded that “[o]verall, these findings can be interpreted as evidence that certain properties that are typically associated with register‐specific vocabulary used with young infants—at least diminutives and reduplication—do indeed facilitate general vocabulary development." (Ota et al, 2018). To put it another way, babies whose parents used more reduplicatives and diminutives when talking to them gained vocabulary more quickly at the initial stage of vocabulary development than those whose parents who used fewer of these types of words. The reason is that baby-talk words teach children how to segment, or extract, individual words from conversation. This is an interesting finding, which may have some relationship to previous research that showed poor word segmentation skills in infancy correlated with language delays seen at 2, 4, and 6 years of age. (Newman, Bernstein Ratner, Jusczyk, Jusczyk, & Dow, 2006).

Don’t Rule Out Iconicity Just Yet

While this particular study did not determine iconicity as beneficial, a number of other studies have found it to be so (Imai, Miyazaki, Yeung, Kidaka, Kantartzis, Okada, & Kita, 2015; Perniss, Lu, Morgan, & Vigliocco, 2017). Ota and his colleagues suggested flaws in their methodology that may not have captured enough adult input, or may not have coded iconicity correctly in their analysis.

Clinical Implications

Ota et al. (2018) highlight the importance of using diminutives and reduplicatives in our child-directed interactions. There are many ways we can highlight the importance of using these specific types of words when coaching caregivers. And while more research is needed, current studies show that this input appears to have the most impact prior to the age of 2, possibly starting as early as 7.6 months of age (Houston & Juszcyk, 2000).

For children older than age 2 who have language delays, baby-talk words may still serve as effective language models. In fact, many of us already share with parents the benefits of using fun CVCV vocabulary to provide their children easier imitation opportunities. By taking what we know from Ota et al’s research, we can be even more purposeful about coaching parents on vocabulary goals, informing them that the words we use today may influence the rate at which their child will gain new vocabulary. When we teach caregivers to OWL™ and follow their child’s lead, they can use iconic, reduplicative, and diminutive words while turn taking.

We also coach caregivers on how to implement predictable activities throughout their day.

In people games like peekaboo and hide and seek, we can encourage words like boo!, bye-bye, mommy, and daddy, during turns.While turn-taking with toys, children will benefit from vocabulary like choo-choo, baby, night-night, horsie, and piggy.During bath time and dressing routines, the words tummy or belly will bootstrap later language acquisition better than stomach.

Again, these are the types of words we already recommend in interactions but now we know that they are essential building blocks for language development, both now and as the child develops. This information can be particularly helpful if you are working with families who are reluctant to use “baby-talk”.

Additional Clinical Value for Intervention with infants

When children under the age of 2 show emerging signs of language delay but may not be immediately referred for services, sharing the function of baby-talk words can be a valuable addition to our set of recommendations to the family for supporting language development.

For those working in Neonatal Intensive Care Unit (NICU) follow up programs, this information can be an important part of the screening process. Sharing the value of using baby-talk words can be added to the set of recommendations at the 6-, 12-, and 18-month visits.

The Final Takeaway

This study makes it clear that the contribution of baby-talk words goes a lot further than providing “fun” words that are easier and more motivating for children to learn. They play a critical role in giving children the tools to facilitate general vocabulary development, which is reflected in the authors’ statement that “…. it is fitting to consider the role of baby-talk words as a bootstrapping device, whose main contribution is to kick-start the process of lexical learning.” (Ota et al, 2018, p. 1994).


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