Compression in the California Vowel Shift: Tracking generational sound change in California's Central Valley

This paper investigates the California Vowel Shift, previously characterized as a chain shift, in communities across California's Central Valley. An incremental apparent time analysis of 72 Californians' vowel spaces provides no clear evidence of a gradual chain shift; that is, changes have not unfolded in an order that reflects an implicational chain in chronological time. Instead, we see contemporaneous movements of vowels that work against the phonological tendency of maximal dispersion typically invoked in describing chain shifts. By analyzing change in the size and dispersion of the entire vowel space, we find that ongoing sound change is instead characterized by a holistic compression of the vowel space. This suggests that, in these California communities, the shift's unfolding was driven by articulatory and social, rather than purely phonological, factors. We propose that the analysis of the size and spread of holistic vowel space can help characterize the nature and motivations for vocalic changes.