Speech and Language Development in Children: Recognition of Words

Have you ever stopped to think about how children learn to speak?

I mean, really stop and think. When a child is born, they're not even physically capable of speech, much less cognitively. A human baby's vocal tract has more in common with an adult chimpanzee than an adult human. Their tongues are positioned solely for the sucking of milk in the first few months. Then, as their brains develop, so do their vocal tracts.

Several studies have been done which showed that babies can hear, and even recognise, speech sounds before they are even born. I won't bore you with all the details here, but it has been shown that babies can recognise differences in speech, and tend to prefer rhyming words over music or rhythmic noises (eg drumming). By 4 weeks of age, a baby has learned to recognise, and prefers, its own mother's voice. Babies seem to enjoy what is known as the prosody of speech; the musical sound speech can have through use of stresses, intonation and rhythm. They can also use this prosody to distinguish between different languages at an early age.

Have you ever been on holiday to Spain, after perhaps having a couple of Spanish lessons, maybe bought a guide book? At home you can sit there and understand a "Teach Yourself Spanish" recording as it says "Por favor, muéstrame dónde están los baños" and the response comes back, "los baños están en ese camino a la derecha." You might repeat those phrases to yourself five or six times... then you walk up to an actual, real life, Spanish person and ask them where the toilets are. And their response is not "the toilets are down that road on the right;" Their response is a long stream of Spanish words, of which you understand maybe the first and the last, and one or two in the middle. Because in Spain, the toilets are never down that road on the right. 

This is how it is for a baby, who has never experienced language before. They understand that you are speaking, but it sounds a lot like a 6-month-old's babbling sounds to us. The first thing an infant needs to do is learn to spot where one word ends, and the next begins. They do this by looking for where syllable stresses are. In the English language, 90% of words have a stress on the first syllable. They also look at something called "transitional probability," which involves the probability of certain combinations of syllables being said side by side. For example, take the phrase: "chicken sandwiches." You hear the syllables chi and ken a lot together, and sand-wich-es too. But how often do you hear the syllables ken and sand side by side? Babies very cleverly use this probability to figure out where words end and begin in sentences. This is also why mothers often naturally find themselves speaking slowly, in simple sentences to their infants, and saying the same words over and over again. All of this helps a child to begin recognising words.

It's also worth noting here that babies' hearing also changes during their first year of life. As I mentioned in this post, babies are born with the ability to hear differences between all sounds. You know when a foreign-speaking person asks you to pronounce a word for them, and you do it, and they repeat it but still say it wrong? It's not because they're stupid. It's because in their native language, that particular sound doesn't exist - so while they were born able to hear it, over the course of their first year of life, their brains have adapted to hear only what they need to hear. This is why you can say "very very" to a Japanese-speaking person, and they will repeat back "vewy vewy" and not hear the difference. Similarly, you can go on your holiday to Spain and say what you think is a perfectly accented, well put together Spanish sentence, and the man behind the counter will say "you're English!" It's because he can hear something you can't hear in those words.

The next part in this series of posts is here