Babies Learn Their Language by Counting Its Sounds

For the first six to eight months of life, babies are what Patricia Kuhl, a researcher who studies language in babies, calls citizens of the world.

That means they can hear the difference between every sound in every language, something adults cannot do. Adults are culture-bound listeners, tuned to their own language and unable to hear some foreign contrasts.

The change happens fast. When Kuhl tested babies in Seattle and Tokyo on the English sounds “ra” and “la,” which matter in English but not in Japanese, six to eight-month-olds in both cities scored the same. Two months later, just before their first birthdays, the American babies had gotten better and the Japanese babies had gotten worse. Each group was preparing for exactly the language it would learn.

What is happening in those two months is counting. As babies listen to motherese, the way adults talk to babies that is found across cultures, they listen intently and take statistics on the language they hear. In Kuhl’s talk, she plays examples from an English-speaking mother and a Japanese-speaking mother.

The counts look different by language. In English, the sounds pile up at two ends, with lots of clear Rs and lots of clear Ls. In Japanese, they pile up in the middle, around an in-between sound often called the Japanese R.

Kuhl says “babies absorb the statistics of the language and it changes their brains,” turning them from citizens of the world into culture-bound listeners. Adults, she says, no longer absorb those statistics in the same way, and are governed instead by the patterns laid down early in life.

By about a year, then, babies have tuned to the sounds they hear around them, ready for their own language even if they no longer hear differences that do not matter in it.