Adults speak FAST, so how do babies ever pick it up?!

It's truly incredible how perceptive babies are when it comes to learning to speak. Assuming there are no hearing or cognitive issues with language development, babies begin (even before birth) with what we call 'segmenting the speech stream'. This is how babies perceive and segregate speech sounds, categorising them into meaningful chunks.

Imagine you've just been plunged into a city where you don't speak the language at all. How do you know where words start and finish? It's all one long stream. As adults we might feel that this is incredibly disorienting and confusing.

But babies are not confused. Babies are linguists and they begin to segment the speech stream and make sense of the sounds around them from mid-pregnancy when their hearing develops. Babies can differentiate speech sounds vs other noises like whistling in their environment.

Here’s an example:

If you listen to an /r/ sound and a /l/ sound, and you're used to hearing English, they sound distinguishably different. Rap and lap mean totally different things, right? We group similar things together but we also filter out any minor differences in how different people say a sound.

So babies hear /p/ in 'pat' from different adults and perceive one sound for /p/not a new sound for each speaker (boy, that would be confusing!)

Different languages group sounds together in different ways.
 In Japanese, the sounds /r/ and /l/ are not perceived as being different sounds but as variations of the *same* sound continuum. This is why it's harder for Japanese adults to hear the difference between /r/ and /l/. However babies can perceive very small nuances in speech sounds (like the /l/ /r/ distinction that Japanese adults cannot perceive easily).


So very cleverly, babies are 'open' to learning where sound boundaries may or may not be in the languages they hear.

Another example is Zulu clicks. Zulu click sounds carry meaning for speakers of Zulu, but are not meaningful speech sounds for adults who do not speak Zulu. They might sound no more meaningful than clicking your fingers, and all sound the same at first, unless you practise hearing the differences.

But English babies of 6–14 months old can perceive the contrasts between Zulu click sounds, according to research by Best and colleagues in 1988. Adults could also perceive the difference: the sensitivity to subtle differences was still there. Maybe adults just need to have confidence in their own listening abilities – something I think we all could work on!

Even at birth babies recognise their mother's voice, and the language(s)that are familiar to them already through their experience in utero. That's right! Even 4-day-old babies have been shown to differentiate French from Russian (but not English from Italian in one experiment) according to Mehler et al. in 1988!

From around 10 months old, babies begin to attune to the sounds they hear most often across all their languages. From their earliest moments of hearing, babies are learning to speak.

Isn't it incredible?!