4. Use Motionese
When adults talk to young children about small objects, they frequently twist the object, or shake it, or move it around — usually synchronized to the sing-song of parentese. This "motionese" is very helpful in teaching the name of the object. Moving the object turns the moment into a multi-sensory experience. This helps attract the infant's attention and ensures that the child attaches the right label to the right object.
Children have better recall for words learned via multi-sensory exposure. But the window to use motionese closes at fifteen months: by that age, children no longer benefit from the extra motion.
Hearing multiple speakers gave the children the opportunity to hear how the phonics were the same, even if the voices varied in pitch and speed. By hearing in the speech what was different, they learned what was the same.
6. Use Frames To Teach New Words
You might think kids need to acquire a certain number of words in their vocabulary before they learn grammar — but it's the exact opposite. Grammar teaches vocabulary.
A typical two-year old hears roughly 7,000 utterances a day. But 45% of utterances begin with one of these seventeen words: what, that, it, you, are/aren't, I, do/don't, is, a, would, can/can't, where, there, who, come, look, and let's. Throw in some two and three word combinations, known as frames, and scholars can account for two-thirds of what a toddler hears in a given day.
These word frames are 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.
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. She heard the past tense of "give," that it's possible to switch nouns from being subjects to direct objects (and vice versa), and that verbs can be used as an instruction to act (Give it) or description of action taken (She gives).
Variation helps, if it's used about 50% of the time. More than that, the sentences become too varied: the kids lose the connection between the sentences.