I have been fascinated by language development since long before I was a mother. It is a window into the extraordinary flexibility and plasticity of the infant brain – you can almost see the neurons firing as they master new words.  From birth to three years old, the brain makes 700 new synaptic connections per second (Kuhl). An absolutely astounding fact, but it becomes easier to imagine when witnessing a toddler making those amazing linguistic leaps – suddenly learning dozens of words each day, or speaking in full sentences for the first time. Even now, with Dani only just cooing, I feel as though I am witnessing magic.

Here’s just a bit of the extraordinary wonder of infant language development: babies are born primed to learn every single language in existence. There are approximately 600 sounds in the human repertoire, and each language uses about 40. Young infants can hear and discern every one of those 600 sounds. And milliseconds after the neurons fire in the parts of the brain responsible for hearing, those responsible for speaking and motor coordination follow – their brains are working on how to respond long before they comprehend the meaning of the words (Kuhl).

Dani’s current motor coordination is limited to mainly vowel sounds – that sweet cooing of the very young. Yet she can speak the vowels of every language on the planet. Which is why it is impossible for me to accurately imitate her coos. I have long since lost the ability to form my mouth into the shapes that make the sounds she so effortlessly utters. In fact, my ears can’t even discern many of them. Sometimes, when she makes a particularly complex coo, I like to imagine the far distant tribe that has included that sound in their language. The first 9 months of Dani’s life are my opportunity to hear the voices of the whole of humankind. What a gift!

At about 6 months old babies begin to discern language-specific vowel sounds, followed by the rhythms of their native language at 8 months, and combinations of sounds around 9 months. But 9-month olds can still easily learn additional languages, even if they are exposed to them for the very first time. Studies have shown that babies from English-speaking households, exposed to one hour per week of Mandarin “tutoring”, were as good at distinguishing Mandarin sounds as those who were raised with it from birth. In another study, 9-month olds were exposed to Spanish “tutoring”. One month later, they were able to babble with a Spanish cadence when interacting with Spanish speakers, then return to English rhythms when interacting with adults speaking English (Kuhl).

Our ability to learn languages decreases slowly until about age 7, when it makes a significant drop. Around puberty, it plummets. (Which is why the American model of teaching foreign languages only in high school is foolish, to say the least.)

There is one major limitation to infants’ wondrous linguistic feats – they require human interaction. The same researchers who studied the ability of American infants to learn Mandarin conducted a follow-up study to see if audio exposure alone would have the same effect. The control group was exposed to one hour per week of Mandarin on TV. The assumption was that the babies were so engaged with the television, they must be learning. The researchers were shocked to discover that both audio and video exposure taught babies the exact same thing – nothing at all (Kuhl).

Subsequent studies have shown the negative impact of TV exposure on language development – for every hour per day of television exposure prior to 16 months, children have 5 less words at 3-years old. The conclusion is that TV cuts down on the amount of talking adults are doing in the household. Studies have also shown that babies learn language best in one-on-one interactions with an adult, and best when the adult is speaking “parent-ease” (Kuhl).

Parent-ease: that lilting, slow, rhythmic way we all speak to babies. It is instinctual and universal, and it benefits babies in multiple ways: the pitch of parent-ease ranges a full octave or more, with wide variation – exaggerated acoustics that catch babies’ attention. And the slow over-articulation pulls the distribution of sounds apart, so each is more recognizable. It also takes effort, requiring engagement and presence to maintain. Which is why across cultures, the only parents who routinely don’t speak to babies in parent-ease are those who are severely depressed.

It is not just the concrete characteristics of parent-ease that make it the juice of baby language development. The magic is in the effort and intention it requires. The key to learning language is in the relationship. Though we don’t know exactly what, there is something hormonal, something neuro-chemical that occurs when we are face-to-face and focused on that sweet interaction. It primes the brain. Which is why babies will do anything to keep the parent-ease flowing for as long as they can maintain their quiet-alert state.

I learned this with Dani soon after she started smiling. I quickly discovered that the best way to keep those smiles coming was to further exaggerate my parent-ease. The more excited, sing-song and slow my voice, the more she rewards me with smiles. She coos back at me, and practices all sorts of shapes with her mouth. And we both benefit from them heart warming glow of attuned interaction. And it is not just our hearts that align – when we are face-to-face and attuned, our neurons actually fire in synchronicity (Kuhl).

Which is why the key to all learning lies in social interaction. “Social learning is the gate to all the cognition that follows” (Kuhl). The idea that we can distinguish cognitive from social-emotional development is a thing of the past. Brain imaging studies are proving what parents have always intuitively known – that it is the quality of our relationships that primes the baby’s brain for optimal development. All that we must learn to be fully human, comes to us within the context of securely attached primary relationships, and the present moment awareness of attuned, attentive parents.


Kuhl, P. (November 7, 2014). Early Learning and the Child’s Developing Brain. Lecture conducted from IPMHPCP, Napa, CA.


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