Effects of local lexical competition and regional dialect on vowel production.

Global measures of lexical competition, such as lexical neighborhood density, assume that all phonological contrasts contribute equally to competition. However, effects of local phonetic similarity have also been observed in speech production processes, suggesting that some contrasts may lead to greater competition than others. In the current study, the effect of local lexical competition on vowel production was examined across two dialects of American English that differ in the phonetic similarity of the low-front and low-back vowel pairs. Results revealed a significant interaction between regional dialect and local lexical competition on the acoustic distance within each vowel pair. Local lexical contrast led to greater acoustic distance between vowels, as expected, but this effect was significantly enhanced for acoustically similar dialect-specific variants. These results were independent of global neighborhood density, suggesting that local lexical competition may contribute to the realization of sociolinguistic variation and phonological change.