The Word Explosion in Infants

Babies first bridge the gap between sounds and meaning as early as nine or ten months of age. They learn the names of family members and pets, the meaning of no! and perhaps a few general labels like shoe and cookie. By his first birthday, the average child understands around seventy words, mostly nouns like people's names and terms for objects, but also certain social expressions, like hi and bye-bye. Of course, he cannot say nearly that many. The median number of words spoken by a one-year-old is six, but many say none at all, and a few speak up to fifty. There's typically about a five-month lag between the time a toddler can understand a certain number of words and when he can actually speak that many.

New words accrue slowly between twelve and eighteen months. Nathan picks up a few nouns and expressions each month—spoon, blankie, nose, milk, up, allgone—trying each out for several days and often dropping them as he moves on to the next. But then, all of a sudden, his vocabulary hits critical mass: he starts saying new words every single day—car, cup, kitty, flower, plane, birdie, teeth, keys, hair, light, foot, let's go, ball, kiss, cracker, doggie, peekaboo, book, dance, water. Gramma, down, night-night, bath-time, eyes, ears. block, phone, bunny, hug, (com)puter, chair, tree, crib ... so many his mother can't keep up with the log she had begun keeping. Fifty is the magic number. Most toddlers' vocabulary explodes once they can say about four dozen words. Now they start adding one, two, or three new words to their speech every day, and their receptive vocabulary—the number of words a child understands—grows even more quickly. Between two and six, children are estimated to learn the meaning of a staggering eight words a day. That comes out to more than one new word every two hours they're awake, and they continue at this rate into the elementary school years. By the time a child is six, it's been estimated that he understands some 13,000 words, although he doesn't speak nearly that many.

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There are really just two basic tricks of grammar used by all the languages of the world. You can create meaning either by adjusting the order of words or by changing the little pieces (known as inflections) that are tacked onto the ends of words (or beginnings, in some languages). For instance, the difference between "Big Bird is tickling Cookie Monster" and "Cookie Monster i tickling Big Bird" is conveyed both by the sequence of words—which proper noun is on which side of the verb—and by the form of the verb, since changing "tickling" to "tickled by" would exactly reverse the meaning of each sentence.

Toddlers begin to appreciate differences in word order before they begin combining words in their own speech. When sixteen-to-eighteen-month-olds were seated in front of a pair of television sets, each showing Sesame Street puppets acting out one of these two sentences, they looked more at the video corresponding to whichever sentence was playing on voice-over. Children thus appreciate the meaning embedded in word order at a very young age, an understanding that becomes quite useful when they begin speaking two-word phrases themselves, usually between eighteen and twenty-four months. Indeed, the vast majority of toddlers' first word pairs are in the proper order, minisentences such as: All dry. I shut. See baby. More cereal. Mail come. Our car.

There is no three-word stage in language development. Toddlers hang for several months in the two-word phase, still rapidly building their vocabularies. Then, beginning early in the third year, they swim into another linguistic vortex, this time the rapid accumulation of grammatical skills. It begins, of course, with the stringing together of more and more words, but the number can be three, four, or even more: J drive car-car. Plane go fast. That big dog^e nice. Now go outside. What the man doing on roof? Though correct in word order, these early sentences tend to lack most of the inflections and little function words—of, to, the, am, do, in, etc.—which is why they are called telegraphic, as if each word were at a premium. Before long, however, two-year-olds start adding little bits of grammar, and this too happens in a strikingly predictable way. English-learning children usually begin with the present participle {-mg) verb ending, as in, Where Mommy going! Then come prepositions such as in and on, followed by plural -s endings (cats), possessive -s endings (hers), articles (the, a), regular past tense endings {-ed), and third person present tense -s endings (walks), to mention just a few.

What's most fascinating about the way children learn grammar is that they are not simply doing it by trial and error; they are figuring out the actual rules for how different classes of words are combined. This means, first of all, that they intuitively grasp the distinctions between different parts of speech—nouns, verbs, adjectives, and so on. Before long, they figure out how to adjust and assemble these various parts to produce the precise meaning they intend. Say, for instance, that four-year-old Daniel is presented with a word he has never seen before: someone shows him a drawing of a birdlike animal and tells him that it is a "wug." If he is next shown a drawing of two such creatures and asked what they are called, Daniel will inevitably say "wugs." He already knows, without ever being taught, how to recognize a noun and make it plural. In fact, there are three different situations in which English grammar requires the use of -s endings, and children master all of them before the age of four, but in a distinct sequence: first, they figure out how to make plurals (dogs, cats, Elmo dolls); then, to use -s to indicate possession (dog's bone. Fluffy s yam, Elmo's doll); and last, to make present tense verbs to agree with a third person singular subject (The dog barks. Fluffy plays with yam. Elmo pees!). That children start adding these different -s's at different times proves that they can distinguish these separate parts of speech and the rules that apply to them; they are not simply imitating individual words or phrases from Mommy and Daddy.

Even more revealing are the mistakes young children make. Though parents may bristle at the sound of them, there's a good reason why older twos. threes, and fours come up with constructions such as: He gots a purple truck; She beed happy; Katie comed over; We swimmed at the pool. Each error is one of overgeneralization; the child takes an irregular verb—one of the roughly i8o in the English language whose past tense is not formed simply by adding -ed to the end—and tries to treat it like a regular verb. Children persist in these mistakes for several years, but the amazing thing is that they tend not to appear in the speech of very young children. In other words, young toddlers will often get a few of these irregular verbs right—like came, was, or has—before they figure out that a rule exists and begin substituting comed, beed, and gots. These errors continue, in spite of adults' correction, until children finally manage to memorize, one by one, all the irregular verb past tenses and override the more convenient rule for regular verbs. Irregular plurals and comparators are a similar source of confusion, which is why you may hear a preschooler describe a trip to the circus thus: The goodest part was those mans with the funny feets!

When children learn about four-dozen words, they suddenly begin to learn many more at an accelerated pace.