Vowel devoicing in Japanese infant- and adult-directed speech

Abstract

It is well known that parents make systematic changes in the way they speak to infants; they use higher pitch overall, more pronounced pitch contours, more extreme point vowels, and simplified morphology and syntax (Andruski and Kuhl, 1996; Fernald et al., 1989). Yet, they also preserve information crucial to the infants ability to acquire the phonology of the native language (e.g., phonemic length information, Werker et al., 2006). The question examined in this paper is whether information other than phonemic segmental information is also preserved, namely, information concerning the phonological process of vowel devoicing. Devoicing of high vowels between voiceless consonants and word-finally after a voiceless consonant is a regular and well-attested phonological process in Japanese (Shibatani, 1990). A corpus of speech by Japanese mothers addressed to their infants and addressed to another adult was examined, and the degree and frequency with which they apply vowel devoicing in each type of speech was analyzed. Rates of vowel devoicing in speech to adults and infants are compared, accommodations made to infants and to hearing-impaired children are discussed (Imaizumi et al., 1995), and the implications of these accommodations for the acquisition of vowel devoicing by Japanese infants are explored.