HOW TO FORMALIZE VARIATION: STOCHASTIC OT MODELS AND /s/ DELETION IN SPANISH

The existence of variability, i.e., when multiple surface forms correspond to a single underlying representation, is a significant problem for many formal theories of phonology, which are often treated as strictly deterministic. Many theorists simply regard the different surface forms as free variants and use optional rules to formalize the variation (see Chomsky & Halle 1968). Others argue that the choice of surface variants is a performance phenomenon, and has no place in a model of grammatical competence (e.g., Bickerton 1971). However, following Labov's early work (e.g., his 1969 article on the copula in AAVE) which demonstrated that the choice of surface variants is conditioned in a consistent and probabilistic manner by several factors, most variationist sociolinguists have assumed inherent variability in the grammar. That is, a speaker's grammatical competence contains knowledge of all of the surface variants, as well as knowledge of how frequently they occur. While variationists working under this paradigm do not always attempt to formalize their empirical findings, when they do, the model they use most commonly is the variable rule (see Labov 1969 and Cedergren & Sankoff 1974 for early formulations). The locus of variation in a speaker's grammar has remained a contentious issue to the present day (see, for example, the exchange between Newmeyer 2003 and Bybee 2005). Recently, however, many phonologists, especially those working within the framework of Optimality Theory (OT), have begun to explore ways in which to extend their formal models to account for variation. Some of the formalisms that have been proposed are Partially Ordered