Vowel Features, Paired Variables, and the English Vowel Shift

In this study the use of variables for the abbreviation of disjunctive sets of phonological rules is examined. We ask whether there are rule sets which require more than one variable, and answer the question in the affirmative. The evidence consists of a new formulation of the English vowel-shift rule, using a pair of asymmetric features which distinguish four tongue heights for vowels. Within the context of the proposed rule, several theoretical issues concerning rule formalism and phonological change are discussed.