| The goal of this thesis is to develop a model of sociolinguistic variation that takes into account "variation above the phonology," namely, variable phenomena that implicate the morphology and/or the syntax. I develop a model under which intra-speaker linguistic variation is the product of two systems: (a) a grammar which derives forms and is partially probabilistic; and (b) a system of language use, distinct from the grammar, which deploys variants based on psycholinguistic and sociostylistic constraints. I illustrate this proposal using data from an in-depth corpus study of the variable contraction of six English auxiliaries. Two sets of findings from the corpus study support the partially probabilistic derivational grammar. First, I show that the patterning of auxiliary forms in spontaneous speech provides evidence in favor of a two-stage model of contraction, under which variation in the morphosyntax is followed by variable phonological processes. This analysis explains a number of patterns in the data which would otherwise be accidental. Second, I examine the linguistic conditions on contraction and argue that they are incompatible with an analysis under which string frequency predicts the occurrence of contraction. Accordingly, internal conditions on contraction are best treated as being encoded in the grammar, rather than as emerging from language use. Evidence in favor of a system of language use distinct from the grammar comes from the finding that contraction shows a strong effect of the number of words in an auxiliary's noun phrase subject, with contraction becoming less and less likely as a subject increases in length. I argue that this effect displays a kind of non-locality which is uncharacteristic of alternations that are the purview of the grammar, and that it should instead be interpreted as stemming from extra-grammatical, memory-based constraints on the system of language production. I localize these constraints, along with sociostylistic constraints on language variation, to a grammar-external system of language use. The dissertation thus provides evidence that variation in surface forms may be attributable to more than one underlying locus, and opens up new lines of research into conditions on variation that have their source in extra-grammatical systems. |
