海角大神

Searching for videos of parents baby-talking to their little ones may sound only marginally more respectable than checking out cat videos as a workday pursuit.

But I had to go looking after reading a recent piece in Scientific American by Patricia K. Kuhl called 鈥淏aby Talk,鈥� about how infants learn to talk 鈥� 鈥渁 mastery,鈥� she notes, 鈥渢hat occurs more quickly than any complex skill acquired during the course of a lifetime.鈥澛�

She discusses fascinating new research into the 鈥渟ensitive period鈥� of just a few months, beginning at age 6 months, when infants are 鈥渕ost open to learning the sounds of a native tongue,鈥� as Professor Kuhl, of the University of Washington, explains it. Vowels come first; consonants follow some three months later. By the time the window closes, infants have 鈥渁cquired鈥� the phonemes of their mother tongue. The window stays open longer for infants exposed to two languages.

Phonemes are the building blocks of a language. The sound of 鈥渂鈥� in 鈥渂aby鈥� is a phoneme in English; ditto the hard consonant at the beginning of 鈥渃at鈥� or 鈥渒itten.鈥� So is each of the 鈥渓ong vowels,鈥� plus their 鈥渟hort鈥� counterparts, and a handful of diphthongs, such as the 鈥渙u鈥� of 鈥渃ouch.鈥�

explains a phoneme as 鈥渢he smallest unit of speech that can be used to make one word different from another word.鈥�

A child who can tell a 鈥渓ake鈥� from a 鈥渞ake,鈥� or a pork 鈥渃hop鈥� from a potato 鈥渃hip,鈥� shows mastery of phonemes.

Linguists estimate that the world鈥檚 languages use 800-plus phonemes. Any given language will use only a of these, typically a few dozen.

But in their sensitive period, infants are 鈥渃itizens of the world,鈥� as Kuhl calls them, able to 鈥渄iscriminate鈥� all 800 phonemes. As they listen to the world around them, they track, like tiny statisticians, the sounds they hear.聽

Kuhl writes, 鈥淐hildren between eight and 10 months of age still do not understand spoken words. Yet they are highly sensitive to how often phonemes occur 鈥� what statisticians call distributional frequencies. The most important phonemes in a given language are the ones spoken most.鈥澛�

This is where 鈥減arentese鈥� comes in 鈥� that high-pitched, singsong patter sometimes simply called 鈥渂aby talk.鈥� Yes, it sounds silly, but it furnishes 鈥渄aily lessons in the intonations and cadences of the baby鈥檚 native tongue,鈥� Kuhl writes.聽

It goes across cultures, but content varies. English-speakers expose their infants to lots of 鈥渞鈥檚鈥� and 鈥渓鈥檚,鈥� for instance; Japanese parents, not so much, because those sounds matter less in Japanese. And 鈥檚 lab has found that, at age 6 to 8 months, Japanese and American infants are about equal in ability to discriminate 鈥渓a鈥� from 鈥渞a鈥�; four months later, Japanese babies lose their ability to make this distinction, but Americans gain.

This transformation of 鈥渃itizens of the world鈥� into what Kuhl calls 鈥渓anguage-bound listeners鈥� is a bit of a downer: It involves letting go of literally hundreds of possibilities. But it anchors children to the sounds of their mother tongue.