Effects of phonetic reduction and regional dialect on vowel production

• Low lexical competition leads to spectral, but not temporal, phonetic reduction.
• Repeated discourse mention leads to both spectral and temporal phonetic reduction.
• A plain speaking style leads to both spectral and temporal phonetic reduction.
• More extreme regional dialect variants are produced in reduction-promoting contexts.

Many linguistic factors contribute to variation in vowel dispersion, including lexical properties, such as word frequency, and discourse properties, such as previous mention. Indexical factors, such as regional dialect, similarly contribute to spectral vowel variation in production. A handful of previous studies have further suggested that linguistic and indexical factors interact such that talkers produce more extreme sociolinguistic variants in linguistic contexts that promote phonetic reduction, such as high frequency and high predictability words. The goal of the current study was to extend the empirical base of this research through an exploration of the interactions between regional dialect and lexical phonological similarity, discourse mention, and speaking style, respectively, on vowel production in Northern and Midland American English. The results revealed more extreme regional dialect variants in reduction-promoting contexts, consistent with previous research. However, substantial variability in phonetic reduction and its interaction with dialect variation was also observed across linguistic contexts, vowel categories, and acoustic domains (temporal vs. spectral), suggesting that a more complex account of the cognitive, linguistic, and indexical factors contributing to phonetic reduction processes is necessary.