Constraints on constraints, or the limits of functional adaptation

The functional approach to typology often appeals to processing pressures in order to explain universals. This paper examines a case where the match between a processing asymmetry and a typological asymmetry is not one-to-one — a case where the functional approach appears to fail. For a particular typology of relative clauses, the psycholinguistic literature suggests two asymmetries: accessibility and parallel function. Only the former shows up as an implicational universal. I argue that the innate language acquisition device imposes a constraint on the adaptability of language. This means that a language that had evolved through a process of linguistic selection to respond to parallel function could not in fact be acquired or represented. In this view all mismatches between processing and cross-linguistic asymmetries are the expected outcome of meta-constraints on cross-linguistic universals.