Learning language

You can't learn the language 'til you know the words. You can't find the words 'til you know the language.
  How do infants learn language?
Consider the newborn. Thrown abruptly into a blaze of bright lights and babble of novel noises, it faces the immediate job of understanding and controlling its world. what are they saying?

Understanding requires the newborn to interpret the strange noises that apparently occur when those giants open their mouths. And controlling means breaking that mysterious sound code that those giants use between themselves and with you.

Crying and fussing may be enough communication for a while, but soon the infant begins babbling by making a sound and rapidly opening and closing the mouth. By 11 to 12 months, the baby is making single words and then joining them into short phrases. By the age of 3 or so, many babies speak in complete sentences, and can express their needs with words (at least after shrieking fails).

How does the newborn learn language? Natural language, after all, is so sophisticated, yet almost all babies learn it faster and more thoroughly than the baddest computer around. Full of nuances, loaded with meaning and implication, language is a subtle but comprehensive mode of communicating.

To most people, it's a hallmark of being human.

That's quite a buildup.
So how do infants learn, already?

Recent research, reported at the American Association for the Advancement of Science meeting in Philadelphia, is putting speculation about how language originates on an experimental basis. Psychologist Richard Aslin of the University of Rochester studies the first step: how infants learn to distinguish individual words. As anyone who's heard a foreign language knows, the spaces between words are only obvious once you know the language. We do not "speak----like----this," but rather with a fluid stream of words.


  A waveform of a sentence. The silences are not where you would expect them. To hear this sentence click here. Source: Jenny Saffran, University of Wisconsin-Madison Psychology department.

It seems to be a chicken-and-egg problem. You can't learn the language until you know the words. But you can't distinguish the words until you know the language.

Working with Jenny Saffran at the University of Wisconsin-Madison, and Elissa Newport at the University of Rochester, Aslin has found one way babies solve this dilemma: by using the pattern of sounds within words to distinguish the ends of words. Babies "pay attention to sounds that cohere within words, compared to the less predictive sounds that change as they span a word boundary," Aslin says. And when that pattern breaks, the baby understands that a new word is about to start.

Faced with this mess of abstraction, The Why Files yearned for an example, and Aslin kindly supplied one -- the phrase "pretty baby." After the first syllable of pretty ("prih") the next syllable is more likely to be something like "tee" than "gond" or "bay." Hearing the expected "tee" sound meant that the word was probably not finished. But when "baby" begins, the unfamiliar pattern ("tee-bay") alerted the infant that a second word had begun.

Howzee know?
Like us, you were wondering how he knew this. Capitalizing on the fact that infants often listen longer to novel sounds rather than boring ones, Aslin measured how long they listened to known and unknown sounds. First he exposed 7- to 8-month-old infants to a nonsense language for two minutes. This musical masterpiece was actually a string of nonsense syllables with no pauses indicating word endings. The selection mixed a series of artificial "words" like "pa bee koo," mixed up in a mass of other syllables.

After hearing the two-minute sequence, the infant would then hear a series of words. Half were "words" taken from the selection, and half were a mishmash of syllables in sequences not heard previously.

From the fact that the infants listening more briefly to the "words," Aslin concluded that the infants could pick out the known words. And since the only way they could have identified the words from the original stream of syllables was by the order of sounds, Aslin asserts that they were identifying words by recognizing those patterns.

A baby step toward language
Distinguishing words is a necessary step to interpreting them, but it's not sufficient. As anybody who's learned a second language knows, words can be ambiguous. What, for example, does the sound "bare" mean? Only the context can tell whether it stands for something hairy, like a "bear cub," or to something bright, like a "bare light bulb."

Before a baby can make these interpretations, he or she must learn to segment words into clauses, groups of words that go together to make up a complete thought within a sentence. "To work out the rules of language, you have to keep stuff together in clauses," says psychologist Peter Jucszyk of Johns Hopkins University.

Clauses seem to play a crucial role from the start. Jucszyk says studies show that 2-month-olds remember words better when they're presented in a clause rather than as individual items in a list.

Jucszyk thinks babies distinguish clauses by learning the melody of a language -- the rhythm of sounds and pauses, the varying pitch in the voice, the different pattern of loudness and softness. (Melody, called "prosody" in the linguistic trade, also helps infants distinguish one language from another. At six months, babies will listen just as long to a foreign language as to their own, but at nine months, they prefer their native tongue.)

So how do they actually learn to talk?

The Why Files
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