The role of grammars in models of language use.

Abstract This paper examines the question of whether and how the grammars proposed by linguists may be said to be ‘realized’ in adequate models of human sentence processing. We first review the assumptions guiding the so-called Derivational Theory of Complexity (DTC) experiments. Recall that the DTC experiments were taken to show that the theory of transformational grammar (TG) known as the Standard Theory was only a partially adequate model for human parsing. In particular, it was assumed (see Fodor et al., 1974) that the DTC experiments demonstrated that while the parser actually used the structural descriptions implicit in a transformational derivation, the computations it used bore little resemblance to the transformations proposed by a TG. The crucial assumptions behind the DTC were that (1) the processing model (or ‘parser’) performs operations in a linear, serial fashion; and (2) the parser incorporates a grammar written in more or less the same format as the competence grammar. If we assume strict seriality, then it also seems easier to embed an Extended Lexical Grammar, such as the model proposed in Bresnan (1978) (as opposed to a TG), into a parsing model. Therefore, this assumption plays an important role in Bresnan's critique of TG as an adequate part of a theory of language use. Both Fodor, Bever and Garrett (1974) and Bresnan (1978) attempt to make the grammatical rules compatible with the psycholinguistic data and with assumption (1) by proposing models that limit the amount of active computation performed on-line. They do this by eliminating the transformational component. However, we show that on-line computation need not be associated with added reaction time complexity. That is, we show that a parser that relates deep structure to surface structure by transformational rules (or, more accurately, by parsing rules tailored very closely after those of a transformational model) can be made to comport with the relevant psycholinguistic data, simply by varying assumption (1). In particular, we show that by embedding TG in a parallel computational architecture—an architecture that can be justified as a reasonable one for language use—one can capture the sentence processing complexity differences noted by DTC experimenters. Assumption (2) is also relevant to the evaluation of competing grammars as theories of language use. First we show that Bresnan (1978) must relax this assumption in order to make Extended Lexical Grammar compatible with the psycholinguistic results. Secondly, we analyze Tyler and Marslen-Wilson's (1977) and Tyler's (1980) claim that their experiments show that one cannot instantiate a TG in a model of parsing without varying assumption (2). This is because they insist that their experiments support an ‘interactive model’ of parsing that, they believe, is incompatible with the ‘Autonomy of Syntax’ thesis. We show that the Autonomy Thesis bears no relation to their ‘interactive model’. Therefore, adopting this model is no barrier to the direct incorporation of a TG in a parser. Moreover, we show why meeting assumption (2), a condition that we dub the ‘Type Transparency Hypothesis’, is not an absolute criterion for judging the utility of a grammatical theory for the construction of a theory of parsing. We claim that the grammar need not be viewed as providing a parsing algorithm directly or transparently (assumption 2 above). Nevertheless, we insist that the theory of grammar figures centrally in the development of a model of language use even if Type Transparency is weakened in the ways that we suggest. Taken together, these considerations will be shown to bear on the comparative evaluation of candidate parsing models that incorporate transformational grammar, extended-lexical grammar, or the Tyler and Marslen-Wilson proposals.