So you might think kids need to acquire a certain number of words in their vocabulary before they learn any sort of grammar—but it’s the exact opposite. Grammar teaches vocabulary.
One example: for years, scholars believed that children learned nouns before they learned verbs; it was assumed children learn names for objects before they can comprehend descriptions of actions. Then scholars went to Korea. Unlike European languages, Korean sentences often end with a verb, not a noun. Twenty-month-olds there with a vocabulary of fewer than 50 words knew more verbs than nouns. The first words the kids learned were the last ones usually spoken—because they heard them more clearly.
Until children are eighteen months old, they can’t make out nouns located in the middle of a sentence. For instance, a toddler might know all of the words in the following sentence: “The princess put the toy under her chair.” However, hearing that sentence, a toddler still won’t be able to figure out what happened to the toy, because “toy” came mid-sentence.
The word frames become vital frames of reference. When a child hears, “Look at the ___,” he quickly learns that ___ is a new thing to see. Whatever comes after “Don’t” is something he should stop doing—even if he doesn’t yet know the words “touch” or “light socket.”
Without frames, a kid is just existing within a real-life version of Mad Libs—trying to plug the few words he recognizes into a context where they may or may not belong.
This key concept—using some repetition to highlight the variation—also applies to grammatical variation.
The cousin to frames are “variation sets.” In a variation set, the context and meaning of the sentence remain constant over the course of a series of sentences, but the vocabulary and grammatical structure change. For instance, a variation set would thus be: “Rachel, bring the book to Daddy. Bring him the book. Give it to Daddy. Thank you, Rachel—you gave Daddy the book.”
In this way, Rachel learns that a “book” is also an “it,” and that another word for “Daddy” is “him.” That “bring” and “give” both involve moving an object. Grammatically, she heard the past tense of “give,” that it’s possible for nouns to switch from being subjects to being direct objects (and vice versa), and that verbs can be used as an instruction to act (“Give it”) or a description of action taken (“You gave”).
Variation sets are the expertise of a colleague of Schwade’s at Cornell, Dr. Heidi Waterfall. Simply put, variation sets are really beneficial at teaching both syntax and words—and the greater the variations (in nouns, verbs, conjugation and placement) the better.
From motionese to variation sets—each element teaches a child what is signal and what is noise. But the benefits of knowing what to focus on and what to ignore can hardly be better illustrated than by the research on “shape bias.”
For many of the object nouns kids are trying to learn, the world offers really confusing examples. Common objects like trucks, dogs, telephones, and jackets come in every imaginable color and size and texture. As early as fifteen months old, kids learn to make sense of the world by keying off objects’ commonality of shape, avoiding the distraction of other details. But some kids remain puzzled over what to focus on, and their lack of “shape bias” holds back their language spurt.
However, shape bias is teachable. In one experiment, Drs. Linda Smith and Larissa Samuelson had seventeen-month-old children come into the lab for seven weeks of “shape training.” The sessions were incredibly minimal—each was just five minutes long and the kids learned to identify just four novel shapes (“This is a wug. Can you find the wug?”). That’s all it took, but the effect was amazing. The children’s vocabulary for object names skyrocketed 256%.
A nine-month-old child is typically-developing if he can speak even 1 word. With the benefit of proper scaffolding, he’ll know 50 to 100 words within just a few months. By two, he will speak around 320 words; a couple months later—over 570. Then the floodgates open. By three, he’ll likely be speaking in full sentences. By the time he’s off to kindergarten, he may easily have a vocabulary of over 10,000 words.