Head position and parsing ambiguity

A strongly principle-based model of parsing seeks to employ principles of the competence grammar directly in language processing. Within grammatical theory, the Projection Principle holds that each level of syntactic representation is a uniform projection of the lexical properties of heads. With respect to parsing this suggests that a phrasal node cannot be projected until the occurrence of its head and thus constitutes a strong empirical hypothesis concerning the fundamental nature of human language processing. This paper contrasts some cross-linguistic predictions made by a specific Grammarderived parsing model against those of a well-known top-down model whose functional motivation is decidedly nonlinguistic. This latter Minimal Attachment model is found to predict significant difficulty with respect to the processing of languages such as Japanese, which display rather different surface properties than English. This problem is not encountered in a model which recognizes the crucial role of heads in licensing argument structure with respect to Processing as well as Grammar. Cross-linguistic parsing differences are attributed to the linear and structural positions of licensing heads which constitute the primary locus of the cross-linguistic variation which is therefore ultimately to be ascribed directly to the Projection Principle.