Why Toddlers' Vocabulary Grows Quickly

By Miranda Hitti
WebMD Health News Reviewed by Louise Chang, MD

Aug. 3, 2007 -- Children's vocabulary often booms in the second year of life, and new research may show how that happens.

Bob McMurray, PhD, of the University of Iowa's psychology department tackled the topic of toddlers' talk. He didn't chat with kids or their parents. Instead, McMurray created a mathematical model to identify the factors that prompt kids' word spurts.

McMurray considered the 2,000 most frequently spoken words of the English language. The list includes easy words and more challenging ones.

McMurray theorizes that there's a tipping point at which children's vocabulary typically takes off.

According to McMurray, kids don't necessarily reach that tipping point by learning one word, then the next, and then another. Rather, it's a matter of learning a mix of words at once -- including simple and not-so-simple words -- and repeating them.

"Children are going to get that word spurt guaranteed, mathematically, as long as a couple of conditions hold," Murray says in a University of Iowa news release.

"They have to be learning more than one word at a time, and they must be learning a greater number of difficult or moderate words than easy ones," McMurray explains. "Using computer simulations and a mathematical analysis, I found that if those two conditions are true, you always get a vocabulary explosion."

McMurray's findings appear in an article in the journal Science.

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