This article proposes that patterns of phonological contrast should be added to the list of factors that influence sound change. It adopts a hierarchically determined model of contrast that allows for a constrained degree of crosslinguistic variation in contrastive feature specifications. The predictions of this model are tested against a database comprising the set of vowel changes in the Al-gonquian languages. The model reveals striking commonalities in the underlying sources of these changes and straightforwardly predicts the previously unrecognized patterning of the languages into two groups: (i) those in which */ε/tends to merge with */i/and palatalization is triggered by */i/, and (ii) those in which */ε/tends to merge with */a/and palatalization is triggered by */ε/. In addition to providing a new argument for the relevance of contrast to phonology, the model also gives us a way to import traditional philological findings into a framework that brings them to bear on theoretical questions.
