Development of adaptive phonetic gestures in children: Evidence from voweldevoicing in two different dialects of Japanese

High vowels between voiceless consonants are often devoiced in many languag es, as well as in many dialects of Japanese. This phenomenon can be hypothe sized to be a consequence of the adaptive organization of the laryngeal ges tures to various conditions, including dialectal requirements. If this theo ry is correct, it may be possible to predict developmental changes in vowel devoicing based on the developmental improvement in the dialect-specific o rganization of the laryngeal gestures. To test this expectation, the develo pmental properties of vowel devoicing were investigated for 72 children of 4 and 5 years of age, and 37 adults in two dialects of Japanese. One was th e Osaka dialect, with a low devoicing rate, and the other the Tokyo dialect , with a high devoicing rate. In the Tokyo dialect, the devoicing rate of c hildren significantly increased and reached an adultlike level by the age o f 5 years, whereas it remained low irrespective of age in Osaka. The vowel devoicing of 5-year-old children exhibited the same characteristics as that of the adults of their respective dialect. These results suggest that chil dren growing up with the Tokyo dialect acquire the articulatory gestures wh ich do not inhibit vowel devoicing by the age of 5 years, whereas children growing up with the Osaka dialect acquire those which inhibit the devoicing of vowels by the same age. The results fit in well with the predictions of the gestural account of vowel devoicing. It is also suggested that learnin g dialect-specific adaptive strategies to coordinate voicing and devoicing gestures as required to attain an adultlike vowel devoicing pattern is a lo ng process: By the age of 5 years children have completed enough of this pr ocess to become members of their dialectal community. (C) 1999 Acoustical S ociety of America. [S0001-4966(99)01008-5].