Presence and absence of epenthetic vowel after a verbal stem defines two patterns of past tense suffixation in Hungarian. A great deal of variation can be explained by abstract phonological representations of the component morphemes and general phonological rules or phonotactic constraints. In the abscence of local phonological conditioning of epenthesis, however, generative approaches consider the choice of pattern arbitrary and relegate whole classes of verbs to exceptional status.
In recent work we showed that direct reference to paradigmatic relations between morphologically related surface forms can help formulate regularities within these `exceptional' classes. Functional considerations like the assessment of the level of contrast and uniformity provide a natural way to capture the distribution of epenthesis by deriving implicational generalizations from a gradient scale of functional fitness in various dimensions. These findings fall outside the explanatory scope of synchronic generative phonology and call for a diachronic usage-based approach.
In this talk, I sketch the outlines of such a dynamic framework. The idea is that biases of language use act as pressures in the selection of linguistic tokens that are processed. Variation in the population of tokens and selection pressure together may lead to the entrenchment of tokens with a higher degree of functional fitness. Such a shift makes it possible for a lexicon to emerge where the categorical boundaries between certain patterns conform to the scales of functional fitness. Such a framework can explain the interaction of functional biases with usage frequency and word length in a plausible way.