Josef Fruehwald (2013)
Telling the difference between phonetic and phonological processes is notoriously difficult. In this dissertation, I attempt to distinguish between the two by examining the rate of change of different vowel variants. I employ a Bayesian Heirarchical Model to do so. According to this method, during phonetic change, phonetic variants rarely become phonologized. In fact phonologization appears to happen at the onset of these phonetic changes in every case.
My favorite figure from this chapter displays the predicted trajectories of /ow/ variants along F2. Note how [owL], representing /ow/ before /l/, is markedly divergent from all the other /ow/ variants from the very beginning.