A Unique Child: the Developing Brain, part 5 - Speech patterns

For centuries, scientists, philosophers and educationists have asked what's special about human language. Do we acquire our native tongue through a domain-specific, biological endowment, or is language learned by domain-general mechanisms in much the same way as other aspects of cognition? The nature/nurture debate continues to this day, but what has changed in recent times is the way in which scientists situate the beginnings of language acquisition, as well as our knowledge of how the brain processes language.

Before we proceed, a brief word on the different aspects of human language. Scientists draw a distinction between speech and language: speech includes the sound patterns of a language, whether intonation is rising or falling, how stress is placed within a word, how the speech organs produce tiny differences in sound such as /p/ at the beginning of a word, /p/ in the middle or end of a word, and so forth. This has little to do with meaning.

Language, by contrast, includes many different components:

• - Semantics (meanings of words/expressions, how words relate to one another in a network of meanings)
• - Morphosyntax (grammar) is composed of morphology and syntax: morphology (parts of words that alter meaning, such as '-s' added to nouns to convey plural, or '-er' added to verbs like dance, bake, run, to convey agency with dancer, baker, runner) and syntax (the rules that govern how words are strung together: 'the boy kicks the girl' means something different from 'the girl kicks the boy', even though the words are identical)
• - Pragmatics (how we take into account another person's state of knowledge - instead of 'Lisa gave it to me' we might say 'Lisa, she's my sister, she gave me the book' - as well as the difference between literal and intended meaning, for example, 'the door's open', meaning 'please close the door')
• - Discourse (a string of sentences in which, for instance, we create a coherent set of narrative events and a cohesive use of pronouns, so that the listener knows who did what to whom, where and when).

These are all aspects of language that a young child has to acquire progressively over developmental time.

Eavesdropping on their future native language

As we saw in the first article in this series ('Life before birth', Nursery World, 20 May), the final trimester sees the foetus busy processing aspects of speech, but not yet language. Indeed, the foetus is sensitive to the intonation patterns of its mother tongue and recognises these at birth. And in the early months of life, much of infant processing is focused on speech, paying particular attention to phonemic differences relative to their native language, for example, /p/ versus /b/, /ee/ versus /oo/. Indeed, research has shown that in the early months of life, babies will prefer to look at a face where the sound and mouth shape match ('ee' with an extended lip shape) than a face which has been contrived to display the rounded shape of 'oo' while emitting the sound 'ee'.

Infants are also very sensitive to differences among language families. For example, English, German and Dutch are what linguists call 'stress-based languages' (doctor has a stress on the first syllable, guitar is stressed on the last syllable, mathematics is stressed on the penultimate syllable). By contrast, French, Spanish and Italian are syllable-based languages (in French, all the syllables in mathematique have equal stress).

Babies born to mothers speaking a stress-based language will differentiate English from Italian during the very first weeks of life, but they will have difficulty differentiating English from German because both come from the same language family. Interestingly, recent research indicates that babies brought up bilingually with two languages from the same language family are able to differentiate the sound patterns earlier than babies brought up monolingually.

Communication starts very early

Although in the very early months of life babies do not actually produce any language, this does not mean that they are not already communicating. One study carried out on twoand five-day-old babies in Leipzig, Wurzburg and Paris made an amazing discovery: when the French babies cried, the crying pattern had a rising pitch, but when the German babies cried, they displayed a falling pitch! So, the intonation patterns learned in the womb actually shape the melody of newborn crying patterns in language-specific ways, which is likely to contribute to postnatal bonding. Moreover, earlier studies had shown that mothers quickly learn to differentiate subtleties in their baby's cries - one for hunger, a slightly different one for pain, and yet another for boredom.

Even before infants start trying to emit language-like sounds, they are very sensitive to communication. They pay enormous attention to faces, mouths, eye-gaze direction and pointing. They even take conversational turns. For example, when the mother talks and then pauses, the baby will fill his part of the 'conversation' with excited leg kicking or raspberry blowing, then pause, while mother takes another turn. It is not long before infants try making speech-like sounds, initially tending to produce a very wide variety of sounds from many languages of the world. But gradually over the first six to nine months, they restrict their repertoire to the sounds from their native tongue.

Indeed, experiments have shown that at six months, babies can discriminate sounds from many world languages, but by around nine to ten months of age, they do worse than six-month-olds on sounds from foreign languages. This is a step forward; their brains are becoming increasingly specialised.

From speech to language

Once infants begin to master the native sounds, the speed with which they start to produce language is astonishing. From a series of single words with initially rather global meanings at the end of the first year, they rapidly start to increase their vocabularies and produce mini-sentences like 'Daddy gone' or 'Mummy shoe'. Sometimes, what seem like three words are initially a single word - 'me-do-it'. But toddlers rapidly break down the component parts of language, so 'me-do-it' soon becomes 'me do it', leading to generalization: mummy do it, me not do it. A budding little linguist starting his journey to becoming a fully-fledged conversationalist!

When language fails to develop typically

There are wide individual differences in the ages at which children produce their first words, their first two-word utterances, and full language mastery. Usually, if the child is communicative in non-linguistic ways, has normal hearing, seems to be understanding what is said to him and is developing healthily in other ways, there is no need for concern about being somewhat late in producing language. However, if a child is not following eye gaze and pointing, if he doesn't turn towards the human voice, or if he has clear difficulties in pronouncing sounds, then it is critical to consult a specialist as early as possible. Sometimes, it is a question of glue ear. But sometimes other medical indications are signalled by language delay, such as autism spectrum disorders, specific language impairment or other genetic syndromes.

It is generally agreed that early intervention, often with a focus on communication rather than language itself, can dramatically improve the situation. If the child is found to have serious hearing impairment, then learning a sign language is an excellent foundation. Sign languages have now been extensively researched and have all the properties of spoken languages: semantics, morphosyntax, pragmatics and discourse. One can whisper in sign, make poetry in sign, and use sign as richly as any of the world's spoken languages.

Language and the developing brain

There is a common belief that language is situated in the left hemisphere of the brain. But this is a simplistic view. First, language processing in the brain changes over developmental time, and second, both hemispheres are usually very active when processing language, even in adults, because the various aspects of language - semantics, morphosyntax, pragmatics, discourse - call on different neural processes. It seems clear that we are not born with brain structures already in place to process language.

Initially, several regions in both hemispheres of the child's brain compete to process the input. By placing little sensors on the child's head which measure the electrical activity when the brain hears auditory input, studies have shown that aspects of syntax are initially processed bilaterally, and only after some years does the left hemisphere become predominant. And, if carried out early in life, left hemispherectomy results in almost perfect language development in the right hemisphere. The infant brain is plastic and can adapt to unusual circumstances, as long as appropriate input is provided.

Studies of language acquisition are one of the most active areas of scientific research among developmental psychologists. They cover multiple aspects of speech and language from the earliest moments of life through the nursery years, and beyond. Indeed, studies of adolescent language demonstrate how this age group influences language change. Just think how wicked and cool have taken on new positive meanings! Language is never static; it changes constantly throughout child development and over mankind's history.

Annette Karmiloff-Smith is a professorial research fellow, Department of Psychological Sciences, Birkbeck University of London. For information on Birkbeck's Centre for Brain and Cognitive Development, visit www.cbcd.bbk.ac.uk/babylab

FURTHER READING

• Albareda-Castellot, B, Pons, F & Sebastian-Galles, N (2010) 'The acquisition of phonetic categories in bilingual infants: New data from a new paradigm', Developmental Science, 10, 1-7

• Bloom, P (Ed) (1993) Language Acquisiton: Core Readings. Brighton: Harvester Wheatsheaf

• Klima, E & Bellugi, U (1979) The Signs of Language. Harvard University Press

• Mampe, B, Friederici, AD, Christophe, A, & Wermke, KL (2009) 'Newborns' cry melody is shaped by their native language'. Current Biology, 19(23), pp1994-1997

• Mills, DL, Coffy-Corins, S & Neville, H (1997) 'Language comprehension and cerebral specialisation from 13-20 months'. Developmental Psychology, 13, 397-445

• Minagawa-Kawai, Y, Mori, K, Naoi, N, & Kojima, S (2007) 'Neural attunement processes in infants during the acquisition of a language-specific phonemic contrast'. J Neurosci, 27, 315-321

• Sheehan, E, Namy, LL & Mills, D (2006) 'Developmental changes in neural activity to familiar words and gestures'. Brain and Language, 101(3), 246-259