Connecting structure and variation in sound change

“Structured heterogeneity”, a founding concept of variationist sociolinguistics, puts focus on the ordered social differentiation in language. We extend the notion of structured heterogeneity to formal phonological structure, i.e., representations based on contrasts, with implications for phonetic implementation. Phonology establishes parameters for what varies and how. Patterns of stability and variability with respect to a given feature’s relationship to representations allow us to ground variationist analysis in a framework that makes predictions about potential sound changes: more structure correlates to more stability; less structure corresponds to more variability. However, even though all change requires variability, not all variability leads to change. Two case studies illustrate this asymmetry, keeping a focus on phonetic change with phonological stability. First, Germanic rhotics (r-sounds) from prehistory to the present day are minimally specified. They show tremendous phonetic variability and change but phonological stability. Second, laryngeal contrasts (voicing or aspiration) vary and change in language contact. We track the accumulation of phonetic change in unspecified members of pairs of the type spelled <s> ≠ <z>, etc. This analysis makes predictions about the regularity of sound change, situating regularity in phonology and irregularity in phonetics and the lexicon. Structured heterogeneity involves the variation inherent within the system for various levels of phonetic and phonological representation. Phonological change, then, is about acquiring or learning different abstract representations based on heterogeneous and variable input