Morphosyntactic Variation

In a series of recent investigations of language change, a group of researchers at the University of Pennsylvania and elsewhere has described the grammatical character and time course of a number of gradual syntactic changes in various European languages.[1] In all of these cases, the languages undergoing change exhibit variation in areas of grammar where we do not find optionality in stable systems. Thus, Late Middle English, in the course of losing the verb-second constraint, manifests a variation between verb-second and simple SVO word order that is not found elsewhere among V2 languages (Kroch 1989b). Similarly, Old English and Yiddish vary between INFL-final and INFL-medial phrase structure in the course of changing from the former option to the latter categorically (Pintzuk 1991, 1993; Santorini 1989, 1992, 1993). Ancient Greek, in the centuries between the Homeric period and the New Testament, evolves from an SOV language to an SVO one, with extensive variation between the two orders during the long transition period (Taylor 1990, 1992). In early Spanish, clitics vary in their behavior between XP’s and X-zero elements; and the language, like Middle French (Adams 1987a, 1987b; Dupuis 1989; Vance 1992), is variably V2 (Fontana 1993). Once again, modern Spanish and French exhibit none of this complexity. Indeed, in no case that we have investigated does the variation associated with syntactic change correspond to a diachronically stable alternation in another language. The discussion to follow is an attempt to explain this fact, extending an argument that we and others have made in the past (see especially Santorini 1992) to the effect that syntactic change proceeds via competition between grammatically incompatible options which substitute for one another in usage. One source of support for this view of syntactic change is the apparently general validity of the “Constant Rate Hypothesis” (Kroch 1989c), according to which, in all surface linguistic contexts reflecting a given syntactic change, usage frequencies change at the same rate. This constant rate effect, described below, shows that changing rates of usage reflect the gradual replacement of one abstract grammatical option by another and that the process of change itself is governed by a grammatically-defined winner-take-all competition. The question then arises as to why change should proceed in this way. In particular, we would like to know how the grammatical options are defined and why they are mutually exclusive. Here we follow the line of recent work in syntactic theory, which has proposed that syntactic variation among languages is due to cross-linguistic differences in the morphosyntactic properties of functional heads, among which we include directionality.[2] Syntactic heads, we believe, behave like morphological formatives generally in being subject to the well-known “Blocking Effect” (Aronoff 1976), which excludes morphological doublets, and more generally, it seems, any coexisting formatives that are not functionally differentiated (see Kiparsky 1982b), in a kind of global economy constraint on the storage of linguistic items.[3] Under a morphological conception of syntactic properties, the blocking effect will also exclude variability in the feature content of syntactic heads, as the resultant variant heads would have the status of doublets. This exclusion, however, does not mean, either for morphology or for syntax, that languages never exhibit doublets. Rather it means that doublets