Barry IS A PIXIE-FACED 3-YEAR-OLD WHO CAN'T yet draw a circle or stack his blocks in a simple pattern. There is little chance he will ever live independently. He may never learn to tie his own shoes. Yet Barry is as chatty and engaging a person as you could ever hope to meet. He knows his preschool classmates-and their parents-by name. When he wakes his mom in the morning, he strokes her cheek and tells her how beautiful she is. Then he asks her how she slept. Barry has Williams syndrome, a rare congenital disorder caused by abnormalities on chromosome 7. Children with the condition share an array of distinctive traits, including weak hearts, elfin faces and extremely low IQs. But they're unusually sociable, and often display an extraordinary feeling for language. Ask a Williams child to name an animal, says Dr. Ursula Bellugi of the Salk Institute's Laboratory for Cognitive Neuroscience, and you may get a fanciful discourse on yaks, koalas or unicorns.
If we learned language in the same way that we learn to add, subtract or play cards, children like Barry would not get much beyond hello and goodbye. Nor, for that matter, would normal toddlers. As anyone who has struggled through college French can attest, picking up a new language as an adult is as simple as picking up a truck. Yet virtually every kid in the world succeeds at it-and without conscious effort. Children attach meanings to sounds long before they shed their diapers. They launch into grammatical analysis before they can tie their shoes. And by the age of 8, most produce sentences as readily as laughter or tears.
Scholars have bickered for centuries over how kids accomplish this feat, but most now agree that their brains are wired for the task. Like finches or sparrows, which learn to sing as hatchlings or not at all, we're designed to acquire certain kinds of knowledge at particular stages of development. Children surrounded by words almost always become fluent by 8, whatever their general intelligence. And people deprived of language as children rarely master it as adults, no matter how smart they are or how intensively they're trained. As MIT linguist Steven Pinker observes in his acclaimed 1994 book "The Language Instinct," "Language is not a cultural artifact that we learn the way we learn to tell time or how the federal government works. It is a distinct piece of [our] biological makeup." Whether they emerge speaking Spanish, Czech or Hindi, kids all acquire language on the same general schedule. And as a growing body of research makes clear, they all travel the same remarkable path.
THE JOURNEY TOWARD LANGUAGE STARTS NOT IN THE nursery but in the womb, where the fetus is continually bathed in the sounds of its mother's voice. Babies just 4 days old can distinguish one language from another. French newborns suck more vigorously when they hear French spoken than when they hear Russian--and Russian babies show the opposite preference. At first, they notice only general rhythms and melodies. But newborns are also sensitive to speech sounds, and they home in quickly on the ones that matter.
Each of the world's approximately 6,000 languages uses a different assortment of phonemes, or distinctive sounds, to build words. As adults, we have a hard time even hearing phonemes from foreign languages. The French don't notice any real difference between the th sounds in thick and then--and to most English speakers, the vowel in the French word tu (ee through rounded lips) is just another oo. Researchers have found that month-old infants register both of those distinctions and countless others from the world's languages. But at 6 and 10 months, they start to narrow their range. They grow oblivious to foreign phonemes while staying attuned to whatever sounds the speakers around them are using.
Acquiring a set of phonemes is a first step toward language, but just a baby step. To start decoding speech, you have to recognize words. And as anyone listening to a foreign conversation quickly discovers, people don't talk one... word... at... a... time. Real-life language-even the melodious "parentese" that parents use with infants--consists mainly of nonstop streams of sound. So how do babies suss out the boundaries? Long before they recognize words, says Peter Jusczyk, a cognitive scientist at Johns Hopkins University, they get a feel for how their language uses phonemes to launch syllables. By the time they're 7 months old, American babies are well accustomed to hearing t joined with r (as in tram) and c with l (as in clam), but they've been spared combinations like db, gd, kt, ts and ng, all of which occur in other languages. And once they have an ear for syllables, word boundaries become less mysterious. Ten / groaning / deadbeats / are / cleaning / a / train on / blacktop makes acoustic sense in English, even if you don't know the words. Te/ rgroanin / gdea / dbea / tsare / cleani / nga/ traino/ nbla / cktop isn't an option.
As children start to recognize and play with syllables, they also pick up on the metrical patterns among them. French words tend to end with a stressed syllable. The majority of English words-and virtually all of the mommy-daddy-baby-doggie diminutives that parents heap on children--have the accented syllable up front. Until they're 6 months old, American babies are no more responsive to words like bigger than they are to words like guitar. But Jusczyk has found that 6- to 10-month-olds develop a clear bias for words with first-syllable accents. They suck more vigorously when they hear such words, regardless of whether they're read from lists or tucked into streams of normal speech. The implication is that children less than a year old hear speech not as a blur of sound but as a series of distinct but meaningless words.
BY THEIR FIRST BIRTHDAY, MOST KIDS start linking words to meanings. Amid their streams of sweet, melodic gibberish, they start to name things-ball, cup, bottle, doggie. And even those who don't speak for a while often gesture to show off their mastery of the nose, eyes, ears and toes. These may seem small steps; after all, most 1-year-olds are surrounded by people who insist on pointing and naming every object in sight. But as Pinker observes, making the right connections is a complicated business. How complicated? Imagine yourself surrounded by people speaking a strange language. A rabbit runs by, and someone shouts, "Gavagai!" What does the word mean? "Rabbit" may seem the obvious inference, but it's just one of countless logical alternatives. Gavagai could refer to that particular creature, or it could have a range of broader meanings, from "four-legged plant eater" to "furry thing in motion." How do kids get to the right level of generalization? Why don't they spend their lives trying to figure out what words like "rabbit" mean?
Because, says Stanford psychologist Ellen Markman, they come to the game with innate mental biases. Markman has shown that instead of testing endless hypotheses about each word's meaning, kids start from three basic assumptions. First, they figure that labels refer to whole objects, not parts or qualities. Second, they expect labels to denote classes of things (cups, balls, rabbits) rather than individual items. Third, they assume that anything with a name can have only one. These assumptions don't always lead directly to the right inference ("I'm not a noying," Dennis the Menace once told Mr. Wilson, "I'm a cowboy"). But they vastly simplify word learning. In keeping with the "whole object" assumption, a child won't consider a label for "handle" until she has one for "cup." And thanks to the "one label per object" assumption, a child who has mastered the word cup never assumes that handle is just another way of saying the same thing. "In that situation," says Mark-man, "the child accepts the possibility that the new word applies to some feature of the object."
Words accrue slowly at first. But around the age of 18 months, children's abilities explode. Most start acquiring new words at the phenomenal rate of one every two hours-and for the first time, they start combining them. Children don't all reach these milestones on exactly the same schedule; their development rates can vary by a year or more, and there's no evidence that late talkers end up less fluent than early talkers. But by their second birthdays, most kids have socked away 1,000 to 2,000 words and started tossing around two-word strings such as "no nap," "all wet" or "bottle juice."
Once kids can paste two words together, it's not long before they're generating sentences. Between 24 and 30 months, "no nap" may become "I don't want nap," and "bottle juice" may blossom into "I wnat juice." When kids hit that stage, their repertoires start expanding exponentially. Between 30 and 36 months, most acquire rules for expressing tense (walk versus walked) and number (house versus houses), often overextending them to produce statements like "I bringed home three mouses." They also start using "function words"--the somes, woulds, whos, hows and aftes that enable us to ask either "Do you like milk?" or "Would you like some milk?"
More fundamentally, they discover that words can have radically different meanings depending on how they're strung together. Even before children start combining words on their own, most know the difference between "Big Bird is tickling Cookie Monster" and "Cookie Monster is tickling Big Bird." That awareness marks the zenith of language development. A chimp can learn to label things, and a high-powered computer can process more information in a minute than any person could handle in a lifetime. But neigher a chimp nor a mainframe is any match for a runny-nose 3-year-old when it comes to reporting who did what to whom. When a chimp with a signboard signals "Me banana you banana you," chances are he wants you to give him one, but the utterance could mean almost anything. Three-year-olds don't talk that way. The reason, most linguists agree, is that natural selection has outfitted the human brain with software for grammatival analysis. As MIT linguist Noam Chomsky realized more than 30 years ago, the world's languages all build sentences from noun phrases ("The big dog") and verb phrases ("ate my homework"). And toddlers who have never heard of grammar identify them effortlessly.
To confirm that point, psycholinguists Stephen Crain and Mineharu Nakayama once invited 3-, 4- and 5-year-olds to interview a talking "Star Wars" doll (Jabba the Hutt). With a child at his side, one researcher would pull out a picture and suggest asking Jabba about it. For example: "Ask Jabba if the boy who is unhappy is watching Mickey Mouse." You can't compose the right sentence-- "Is the boy who is unhappy watching Mickey Mouse?"--unless you recognize the-boy-who-is-unhappy as a single noun phrase. As Chomsky would have predicted, the kids got it right every time.
If the children's minds were open to all the possible relationships among words, they would never get very far. No one could memorize 140 million sentences, but a kid who masters 25 common recipes for a noun phrase can produce more than that number from scratch. Too much mental flexibility would confine children, Pinker observes; "innate constraints set them free." Not everyone is blessed with those constraints. Kids with a hereditary condition known as Specific Language Impairment, or SLI, never develop certain aspects of grammar, despite their normal IQs. But those are rare exceptions. Most kids are so primed for grammatical rules that they'll invent them if neccessary.
Consider hearing adults who take up American Sign Language so they can share it with their deaf children. They tend to fracture phrases and leave verbs unconjugated. Yet their kids still become fluent, grammatical signers. "Children don't need good teachers to master language," says Elissa Newport, a cognitive scientist at the University of Rochester. "They pick up whatever rules they can find, and sharpen and extend them." That, according to University of Hawaii linguist Derek Bickerton, is why the crude pidgins that crop up in mixed-language communities quickly evolve into fully grammatical creoles. When language lacks a coherent grammar, children create one.
That's not to say language requires no nurture. Children raised in complete silence grow deaf to grammar. "Chelsea," whose correctable hearing problem went untreated until she was 31, eventually learned enough words to hold a job in a vet's office. Yet her expressive powers have never surpassed those of a chimp with a signboard. She says things like "The woman is bus the going" or "I Wanda be drive come." Fortunately, Chelsea is a rare exception. Given even a few words to play with, most kids quickly take flight. "You don't need to have left the Stone Age," Pinker says. "You don't need to be middle class." All you need to be is young.
People the world over alter their way of speaking when they address infants and toddlers. The effects of "parentese" (originally called "motherese") continue to be hotly debated, but "a number of [its] features are likely to facilitate language learning," says linguist Naomi Baron of The American University. Among them:
Higher pitch captures a child's attention. Speaking more slowly, and with careful enunciation, makes it easier for the baby to distinguish individual words; emphasizing or repeating one word ("Isn't that a huuuuuuge huge doggie?") also helps.
Short utterances help the child grasp grammar more readily than Faulknerian monologues. Don't abandon complex sentences entirely, though: toddlers whose parents use many dependent clauses ("because. . ." and "which. . .") learn to do so earlier than the children of parents who do not.
Repeating a child's utterances ("That's right! It's a birdie") assures her she's been understood. Recasting what the child says ("Want cookie?" "Would you like a cookie?") expands her repertoire. The only aspect of parentese that may impede language development: substituting proper nouns for pronouns ("Does Billy want to swing?"). These are tricky to master (your "you" is my "I"), and toddlers should be exposed to them.
Even normal children whose ears are filled with parentese may refuse to speak. Some delays can be harmless, but those after the age of 3 may affect how well a child will read, write and even think.
0-3 months. Does not turn when you speak or repeat sounds like coos.
4-6 months. Does not respond to "no" or changes in tone of voice, look around for sources of sound like a doorbell, or babble in speechlike sounds such as p, b and m.
7-12 months. Does not recognize words for common items, turn when you call her name, imitate speech sounds or use sounds other than crying to get your attention.
1-2 years. Cannot point to pictures in a book that you name or understand simple questions ("Where is your Teddy?").
2-3 years. Can't understand differences in meaning ("up" vs. "down"), follow two requests ("please pick up the bottle and give it to me"), string together two or three words or name common objects.
3-4 years. Does not answer simple "who," "what" and "where" questions. Cannot be understood by people outside the family, use four-word sentences or pronounce most phonemes correctly. If delays persist until kindergarten, most pediatricians recommend speech therapy.