The long-term objectives of this basic research are to specify the distinctive acoustic patterns in speech signals that differentiate the vowels in different languages and to understand the processes by which listeners recover the linguistically-relevant message from the complex acoustic signals. The goal is to investigate the acoustics and perception of vowels as they occur in continuous speech so that results may be generalized to actual situations. A specific focus of the proposed research is to explore how vowels vary acoustically with local and global situations. (immediate phonetic and phonotactic context, speaking style, speaking rate, sentence prosody) and to investigate how these acoustic variations affect the perception of non-native vowels by second language learners. Three sets of studies are proposed: (l) cross-language comparisons of acoustic variation in vowels of American English (AE), North German, Danish, German French, and Japanese; (2) studies of cross-language perceptual similarity of vowels by AE listeners judging Danish, German and French vowels and by Japanese listeners judging AE and German vowels; and (3) perceptual training studies which investigate the effects of perception training on the production and perception of difficult non-native vowels by adult learners of a foreign language (AE speakers learning German and French, Japanese speakers learning English). These studies will contribute to our understanding of how experience with a particular language shapes inborn capabilities. Results will allow us to make better predictions about problems facing adult foreign language learners and to develop techniques for foreign language instruction and accent reduction. Results will also provide evidence relevant to current theories about native-language phonological representation. Development of better theories of speech perception and production in normal children and adults form the basis for advances in research into problems of atypically developing children with phonological disorders.