What's the best way for toddlers to acquire verb meaning?

New research is shedding light on what kind of sentences are best at facilitating the growth of toddlers' vocabularies. 

A new study conducted at Northwestern University provides evidence that toddlers can learn verbs after hearing them only twice.

Sandra R. Waxman, Louis W. Menk Professor of Psychology at Northwestern University and Sudha Arunachalam, formerly a postdoctoral fellow at Northwestern, note that previous studies have shown that children as young as two years of age can successfully learn novel verbs after they've heard the verb many times while looking at a corresponding visual scene.

However, Waxman said, the key to the toddlers' success is how the verb is "packaged."

For example, if a dad says to his two-year-old toddler, "I see a boy, and a balloon. I see waving," and another dad says to his two-year-old toddler, "A boy is waving a balloon," is one of them more likely to learn the verb "waving" than the other?

The researchers said yes.

Arunachalam, lead author of the study and currently assistant professor of speech and hearing sciences at Boston University, and Waxman, director of Northwestern's Project on Child Development, looked into which of these ways of introducing novel verbs is most helpful to toddlers.

In a series of experiments, toddlers were introduced to six different novel verbs presented in one or two sentences of varying complexity. Some heard the verb in a single sentence that also included two nouns such as, "A boy is gonna pilk a balloon! Let's see!"

Others heard the verb in simpler constructions in which the familiar nouns were mentioned in one sentence and the new verb in another, such as "Let's see a boy and a balloon. Let's see pilking!" Then, both groups watched a short video clip of a boy waving a balloon.

Afterwards, the toddlers were shown two different pictures—one with the same object, but a different action being performed on it (e.g., tapping the balloon), and one with the target action being performed on a new object (e.g., waving a rake). The toddlers were asked to point to "pilking."

Only the toddlers who heard the verb in the same sentence with both nouns (e.g., "The boy is waving a balloon") were able to successfully identify the target action.

"The results offer two insights," Arunachalam said. "First, by age two, toddlers have the remarkable ability to learn new verbs with very little exposure and apply them in novel contexts. Second, presenting the verbs in complete sentences supports the toddlers' abilities to do so. These findings highlight the positive impact that rich communication can have on two-year-olds' burgeoning linguistic abilities."