The Institute is over and I’m back in Houston after my month in academic fairyland. If my intentions pan out, I’ll be writing a series of posts on various things I went to at the Institute.
Let’s start with Bill Labov’s lecture on defining sound change and explaining diffusion and isogloss bunching. [The paper is available here.] The problem he began with was why we get dialect differentiation (particularly dialect scarps) which don’t correspond to natural boundaries. All else being equal, we expect people who are in continued contact with one another to speak the same way, yet there are isogloss boundaries that cross-cut long-established social areas.
Labov looked at the Northern Cities shift. The argument goes like this: there are well-defined properties of chain shifts involving raising and diphthongisation. Peripheral vowels diphthongise, central vowels peripheralise, and the converse doesn’t happen, for various phonetic reasons. Furthermore, chain shifts are irreversible. Therefore, it’s possible to get extensive shifts, and bunching isoglosses, from purely linguistic structural reasons.
That argument seems reasonable in itself, but it’s a big step from that to a generalised model of diffusion and differentiation. For example, we also know (e.g. from Labov’s own work) that we find ad hoc changes through dialect borrowing in adults, and that quasi-reversals can occur in kids in dialectally diverse areas (e.g. with /ay/-mono-vs-diphthongisation in Houston (work by Pantos and Gentry). Furthermore, this account doesn’t handle isogloss fans, where there’s both bunching and non-bunching.
Still, it was nice to see a talk historical linguistics get such a big audience!