title: The multidimensional nature of hyperspeech: evidence from Japanese vowel devoicing.
abstract: We investigate the hypothesis that infant-directed speech is a form of hyperspeech, optimized for intelligibility, by focusing on vowel devoicing in Japanese. Using a corpus of infant-directed and adult-directed Japanese, we show that speakers implement high vowel devoicing less often when speaking to infants than when speaking to adults, consistent with the hyperspeech hypothesis. The same speakers, however, increase vowel devoicing in careful, read speech, a speech style which might be expected to pattern similarly to infant-directed speech. We argue that both infant-directed and read speech can be considered listener-oriented speech styles-each is optimized for the specific needs of its intended listener. We further show that in non-high vowels, this trend is reversed: speakers devoice more often in infant-directed speech and less often in read speech, suggesting that devoicing in the two types of vowels is driven by separate mechanisms in Japanese.
authors.affiliation: Laboratory for Language Development, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan. Electronic address: amartin@brain.riken.jp.
authors.forename: Andrew
authors.initials: A
authors.lastname: Martin
authors.affiliation: Laboratory for Language Development, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan; Nagoya University, Graduate School of Languages and Cultures, Furo, Chikusa, Nagoya 464-8601, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Utsugi
authors.affiliation: Laboratory for Language Development, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan; Duke University, Department of Psychology and Neuroscience, Box 90086, 417 Chapel Drive, Durham, NC 27708-0086, United States.
authors.forename: Reiko
authors.initials: R
authors.lastname: Mazuka
mesh_terms: D000328:Adult; D044466:Asian People; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007564:Japan; D007802:Language; D007804:Language Development; D008297:Male; D009035:Mothers / Q000523:psychology; D013060:Speech / Q000502:physiology*; D013061:Speech Acoustics
keywords: Hyperspeech; Infant-directed speech; Japanese; Phonological rules; Read speech