Linguistic and Cognitive Explanation in Optimality Theory

Generative linguistics aims to provide an analysis of the grammar-forming capacity that individuals bring to the task of learning their native language (Chomsky 1965, 1981, 1991, 1995). Pursuing this goal amounts to developing a linguistic theory that achieves maximum universality and generality in its premises, while at the same time offering explicit, limited means for representing possible interlinguistic variation. The term “Universal Grammar” is used to refer to the system of principles defining what the grammar of a human language can be. Optimality Theory (Prince and Smolensky 1993) asserts that Universal Grammar provides a set of general, universal constraints which evaluate possible structural descriptions of linguistic objects. These constraints are assumed to be strongly universal, in the sense that they are present in every grammar; they must be simple and general if they are to have any hope of universality. The structural description that is grammatical for a linguistic object in a given language is the one, among all possible structures assignable to that object, which is optimal, in the sense that it best satisfies the universal constraints, given the defining characteristics of that object. The theory builds from a notion of “best satisfaction” — optimality rather than perfection — because constraints are often in conflict over the well-formedness of a given candidate analysis, so that satisfying one constraint entails violating others to varying degrees. Indeed, an optimal structural description will typically violate some (or many) of the constraints, because no possible description satisfies all of them. Differences between languages then emerge as the different ways allowed by the theory for resolving the conflicts that are inherent in the universal constraint set. The theory is therefore one of constraint interaction: the effects of any constraint are determined both by its intrinsic demands and by its relation to the other constraints; fixing the relations between the universal constraints defines the grammar of a particular language. Interactionism is the heart and soul of the theory: it places a heavy empirical burden on the positing of constraints, since all interactions must yield possible grammars; it leads to a pattern of explanation in which many universally observed properties of language follow not from hypothesized special principles designed to encode them directly, but from nothing more than the interaction of more general constraints which are not specifically concerned with those particular properties; it opens the way to tremendous simplification of the constraints themselves, since they need not contain codicils and complications that emerge from interaction; and, at the methodological level, it enforces the research ethic that posited constraints must not contain such codicils and complications, thereby guiding the search for a general understanding of the nature of the constraints active in human language. This essay presents an overview of selected work making use of Optimality Theory, with the goal of illuminating these general ideas. Section 1 presents and illustrates the central principles of Optimality Theory. Section 2 gives an example of syntax within the theory. Section 3 examines possible implications of Optimality Theory for studies of language processing, discussing work on the computability of Optimality Theoretic grammars, as well as some conceptual similarities between Optimality Theory and work in connectionism and dynamical systems. Section 4 discusses work on language learnability and acquisition within Optimality Theory.