It’s a no-brainer that babies learn language from their caregivers, but how we respond to them rather than simply how much we talk could have the greater impact, according to a new study in the journal PLOS ONE.
Babies who received an adult response to their sounds had “larger productive vocabularies”, the researchers found, although expansion had the greatest correlation with increased words, followed by recasting, or correcting, the sound.
Specifically, including their word-like babbles in a response – by imitating, correcting or expanding on them – was linked to increased vocabulary. If a baby says “ba”, for instance, the adult could respond “ba”, “ball” or “yes that is a big red ball”.
“Over merely talking to your infant, we found that parents who respond to their infants’ babbles with word and sentence corrections have infants who say more words,” write Lukas Lopez, from the University of California, US, and colleagues.
Importantly, the research was conducted in a naturalistic home setting, and its results support findings from experiments exploring infant-directed speech in the lab or with research onlookers – quality trumps quantity.
Results also confirmed a two-way effect, or a “positive feedback loop”: infants who produced more speech-like babbling sounds had a larger vocabulary and in turn received more adult responses.
The study used audio recordings collected using wearable devices for a minimum of 10 hours from 53 babies aged 13 months. Six five-minute segments were hand-coded for each child, totalling 30 minutes, allowing the researchers to capture a range of unique activities and settings.
Caregivers were asked to report the size of their baby’s vocabulary by completing nearly 400 items on the validated MacArthur-Bates Communicative Development Inventory (MBCDI).
Intriguingly, responding to “non-canonical” sounds – those that don’t resemble any words – was associated with poorer infant vocabulary, which the authors say adds to evidence suggesting that speech-like sounds prompt more caregiver responses.
The findings add to a growing body of research aimed at unravelling infant vocabulary development and how it can be optimised, particularly for those who struggle with learning language.
Language development starts early, and from seemingly non-sensical sounds. “The communicative value of pre-linguistic infant vocalisations should not be downplayed”, the authors write.
“From birth, infants produce reflexive vocalisations, such as cries, fusses, and vegetative noises [such as] coughs, burps, sneezes.”
By three months, their vocal repertoire expands to include “raspberries, squeals, growls, full vowels, yells, whispers, and primitive consonant-vowel syllables known as marginal babbling”.
This transitions to “canonical babbling” by around seven months, which includes consonants and is deemed speech-like.
Natalie Parletta is a freelance science writer based in Adelaide and an adjunct senior research fellow with the University of South Australia.
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