HIGHLIGHTS

NATURE REVIEWS | NEUROSCIENCE VOLUME 4 | SEPTEMBER 2003 | 1

URLsKuhl lab:http://cmbl.washington.edu/kuhl/

Many of our readers will have first-hand experience of the problemsinvolved in learning a new languageas an adult. As well as having to mem-orize new vocabulary and grammar,we often come across sounds that wecannot distinguish from each other,even though they sound quite differ-ent to a native speaker. Althoughyoung infants can distinguishbetween all of the sounds used in dif-ferent languages, this ability declinessharply between six and twelvemonths of age, when they start tospecialize in their own language. Astudy in Proceedings of the NationalAcademy of Sciences shows that theability to perceive phonetic units canreadily be rescued during this time —but only by social interaction withforeign-language speakers.

Given that infants can acquiremore than one language, the loss of

foreign-language speech perceptioncannot be inevitable. Kuhl et al. inves-tigated how much, and what kind, ofexposure to a second language isneeded to prevent the decline in per-ception of its phonetic units. Theyexposed 9-month-old English-speak-ing infants to about five hours ofMandarin speech, in short sessionsover four weeks. The Mandarinspeakers read children’s stories andinteracted with the infants naturally.

Even this short exposure to a for-eign language was enough to reversethe decline in perception ofMandarin speech sounds seen in acontrol group. Crucially, though, asimilar amount of exposure to eitheraudio or audiovisual recordings ofMandarin speakers had no effect,indicating that social interactionmight be vital for phonetic learningat this age. Interestingly, other species,

such as songbirds, also learn commu-nication skills more easily when cuedby social interactions.

A predisposition to learn languageskills during interactions with peoplewould help infants to learn appropri-ately, rather than being influenced bynon-language sounds in the environ-ment. Previous work has shown thatadults instinctively use ‘motherese’when speaking to infants — theyexaggerate their vowel sounds in away that facilitates language learning.But the new results show that othercues, such as body language and gazedirection, might also be a crucial partof the collaboration between infantsand their parents that enables suchremarkable language learning duringthe first years of life.

Rachel Jones

References and linksORIGINAL RESEARCH PAPER Kuhl, P. K. et al.Foreign-language experience in infancy: effects ofshort-term exposure and social interaction onphonetic learning. Proc. Natl Acad. Sci. USA 100,9096–9101 (2003)WEB SITESKuhl lab: http://cmbl.washington.edu/kuhl/

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