Vocal Development in English- and Chinese-learning Infants

The dissertation focuses on infant vocal development in English- and Chinese-learning infants during the second half year of life. Prior research on ambient-language effects in babbling has often suggested infants produce language-specific phonological features within the first year. These results have been questioned in research failing to find such effects and challenging the positive findings on methodological grounds. The first study (Chapter 2) investigated English- and Chinese-learning infants at 8, 10, and 12 months and found listeners could not detect ambient-language effects in the vast majority of infant utterances, but only in items deemed to be words or to contain canonical syllables that may have made them sound like words with language-specific shapes. Thus, the first study suggests the earliest ambient-language effects may be found in emerging lexical items or in utterances influenced by language-specific features of lexical items. Even the ambient-language effects for infant canonical syllables and words were very small compared with ambient-language effects for meaningless but phonotactically well-formed syllable sequences spoken by adult native speakers of English and Chinese. The first study indicates that canonical syllables are likely to contain language-specific elements compared with non-canonical syllables. Following the results of the first study, the second study (Chapter 3) further investigated the development of canonical syllables across different social circumstances (during infant-directed speech, during infant overhearing of adult-directed speech, or when infants were alone) in the two groups of infants. By evaluating the influence of language and social circumstances on infant vocal development we address the nature of very early language foundations and how they can be modulated. This study evaluated the effects of circumstances. The research examined these circumstances in English- and Chinese-learning infants and measured vocal development in terms of canonical babbling ratios (CBR=canonical syllables/total syllables) at 6 and 11 months in randomly-sampled all-day home recordings. The results in fact showed a complicated interaction of infant age x infant language x social circumstance. The complexity of the results forces us to recognize that a variety of factors can interact in the development of foundations for language