The role of duration in regional U.S. vowel shifts

Contemporary American dialect research has produced a rich body of literature on phonetic differences in vowel production. Many studies have focused on contrasting vowel shifts occurring in the speech of Northerners and Southerners. While such research clearly shows formant differences across dialects, the investigation of regionally variable phonetic cues beyond F1 and F2 has been under-addressed. The limited work that exists on sociolinguistic aspects of duration suggests that speakers do show durational differences across regions [Clopper et al. (2005), Jacewicz et al. (2007), Labov and Baranowski (2006), Tauberer and Evanini (2009)]. However, beyond these studies, there has been little research on the regional variability of vowel duration and on how phonemically non-distinctive durational differences found across regions may be related to the degree and type of spectral shift present in individuals' systems. In this paper we consider the extent to which duration corresponds to spectral differences in the major U.S. vowel shifts. In addition to looking at overall regional patterns, we examine whether durational differences co-vary with degree of individuals' participation in spectral shift. We discuss how duration, particularly of lax vowels, is related to the advancement of vowel shift features and whether such a relationship supports a physiological or grammatical explanation for duration.