% The dissertation abstract can only be 350 words.
This dissertation examines the development of voiceless sibilant fricatives in children speaking English, Japanese or Mandarin Chinese. Both English and Japanese have a two-way distinction in sibilant fricatives (alveolar /s/ vs.post-alveolar /S/ in English and dental/alveolar /s/ vs. alveolopalatal /c}/ in Japanese), and Mandarin Chinese has a three-way contrast among dental/alveolar /s/, alveolopalatal /c}/ and retroflex /S/. Children's fricative productions have been traditionally described using adult's impressionistic transcriptions, which yield inconsistent orders of acquisition both across children and across languages. This dissertation argues that transcription filters children's early productions through adults' language-specific phonological systems, and therefore obscures the actual developmental patterns in children's speech. The purpose of the current study is to tease apart children's own productions from adults' interpretations of them by applying acoustic analyses to both adults' and children's productions and by systematically evaluating adults' perception patterns in tasks that allow more continuous responses. This dissertation first starts by examining the acoustics of adult productions in all three languages to parameterize the acoustic space for sibilant fricatives. It then investigates the production patterns of children speaking either English or Japanese, which has a two-way contrast in voiceless sibilant fricatives. Twenty 2-to-3-year old speakers of each of the two languages were tested to look for covert contrast in children's speech. The results show that adults are not able to recognize fine-grained phonetic differences that children make, and a more objective description of children's productions using methods such as acoustic analysis is needed. A set of perception experiments was then performed to further examine how English-speaking adults and Japanese-speaking adults would differ in judging these 2-3 year olds' productions. The results of this set of perception experiments show that English adults and Japanese adults correlate different acoustic cues with their fricative categories. These production and perception experiments were further extended to other age groups and to Mandarin Chinese in order to make more robust generalizations on the crosslinguistic production and perception patterns. The results suggest that children's early productions are intermediate and variable, with no clear category distinctions, and adults categorize these gross productions in language-specific ways. That is, children start by making some undifferentiated lingual gestures in the multidimensional acoustic space, and as their age increases, they separate out categories in the parameters that are salient in adult productions, which are also cues that adults use in judging children's productions.