Phylogeny and ontogeny of vowel perception

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In this project the perception of vowels were studied in human babies, chimpanzees and Japanese monkeys. Vowels, for example[a], when pronounced by different speakers, have different acoustic properties. For example, the fundamental frequency and formant frequencies of vowels are higher in females and children than in males. However, humans can perceive these speech sounds as the same vowel. This phenomenon has been called vocal tract normalization and has been considered to be an important aspect of speech perception and one of the prerequisites for human speech. Human listeners appear to represent speech categories with reference to a good instance or prototype of the category. It has been suggested that human adults and human infants exhibit a "perceptual magnet effect" for the prototype of speech categories. In this project, vocal tract normalization and the magnet effect were studied.To Study the ability of vocal tract normalization, synthetic Japanese vowels pronounced by both fe … More male and male speakers were introduced. A[o]-[a]continuum was synthesized and the shift of the boundary between these two vowels were examined. Human adults, preschool infants of 3-5 years of age, human babies of 5-7 months of age, chimpanzees and Japanese monkeys were served as subjects. FiLinian babies were studied by the head-turn procedure and apes and monkeys were examined by the reaction time task. Human adults and preschool children, chimpanzees and Japanese monkeys showed the ability of vocal tract normalization. Three of the 5 human babies showed the ability of vocal tract normalization. It is necessary to increase subjects and to improve the head-turn technique which was recently learned from Dr. Kuhl.To study the magnet effect, a [u]-[i]continuum was synthesized. Although chimpanzees have the vowel-like sound which heard as [u], they do not have [i]. In other words, they do not have the prototypic [i]. Thus, they may show the magnet effect only for [u]. The effect was studied by the reaction time task. The results showed that chimpanzees have the prototypic [u], but do not have the prototype of [i]. Swedish have the vowel [y] between [i] and [u], which is not in English. It is of interest to examine when Swedish babies acquire prototype of [y]. Dr. Kuhl showed that they have the prototypic [y] at 6 months of age. Less