Enhanced contrast for vowels in utterance focus: a cross-language study

The present study examined several potential distinctiveness-enhancing correlates of vowels produced in utterance focus by talkers of American English, French, and German. These correlates included possible increases in vowel space size, in formant movement within individual vowels, and in duration variance among vowels. Each language group enhanced the distinctiveness of vowels in [+focus] context but used somewhat differing means to achieve this. All three groups used spectral differences, but only German talkers used durational differences, to enhance distinctiveness. The results suggest that the amount of distinctiveness enhancement of a vowel property in [+focus] context is positively related to the between-category variation of that property in [-focus] context. Thus, consistent with the theory of adaptive dispersion, utterance clarity appears to vary directly with information content.