The Language Explosion

Grammar

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.