Grammar Viewed as a Functioning Part of a Cognitive System

GRAMMAR VIEWED AS A FUNCTIONING PART OF A COGNITIVE SYSTEM Helen M. Gigley Department of Computer Science University of New Hampshire Durham, NH 03824 ABSTRACT How can grammar be viewed as a functional part of a cognitive system) Given a neural basis for the processing control paradigm of language performance, what roles does 'Sgrammar" play? Is there evidence to suggest that grammatical pro- cessing can be independent from other aspects of language processing? This paper will focus on these issues and suggest answers within the context of one com- putational solution. The example model of sen- tence comprehension, HOPE, is intended to demon- strate both representational considerations for a grammar within such a system as well as to illus- trate that by interpreting a grammar as a feedback control mechanism of a "neural-like" process, additional insights into language processing can be obtained. 1. Introduction The role of grammar in defining cognitive models that are neurally plausible and psycho- logically valid will be the focus of this paper. While inguistic theory greatly influences the actual representation that is included in any such model, there are vast differences in how any grammar selected is "processed" within a "natural computation" paradigm. The processing does not grow trees explicitly; it does not transform trees explicitly; nor does it move constituents. In this type of model, a grammar is an ex- plicit encoded representation that coordinates the integrated parallel process. It provides the interfaces between parallel processes that can be interpreted within semantic and syntactic levels separately. It furthermore acts as a "conductor" of a time-synchronized process. Aspects of how a grammar might be processed within a cognitive view of sentence comprehension will be demonstrated within an implemented model of such processing, HOPE (Gigley, 1981; 1982a; 1982b; 1983; 1984; 1985). This view of grammatical "process" sug- gests that neural processing should be included as a basis for defining what is universal in lan- guage. 2. Background There are currently several approaches to developing cognitive models of linguistic function (Cottrell, 1984; Cottrell and Small, 1983; Gigley, 1981; 1982a; 1982b; 1983; 1984; 1985; Small, Cottrell and Shastri, 1982; Waltz and Pollack, in press). These models include assumptions about memory processing within a spreading activation framework (Collins and Loftus, 1975; Hinton, 1981; Quillian, 1968/1980), and a parallel, interactive control paradigm for the processing. They differ in the explicit implementations of these theories and the degree to which they claim to be psycho- logically valid. Computational Neurolinguistics (CN), first suggested as a problem domain by Arbib and Caplan (1979), is an Artificial Intelligence (AI) ap- proach to modelling neural processes which sub- serve natural language performance. As CN has developed, such models are highly constrained by behavioral evidence, both normal and pathological. CN provides a framework for defining cognitive models of natural language performance of behavior that includes claims of validity at two levels, the natural computation or neural-like processing level, and at the system result or behavioral level. Using one implementation of a CN model, HOPE (Gigley, 1981; …

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