A Linear Approach to Multiple Clause Embedding

It is generally accepted among psycholinguists that real-time human sentence processing proceeds incrementally from left to right (see for example Mazuka & Itoh 1995). Recently proposals have been made in the domain of syntax to reduce phenomena which have hitherto been accounted for in terms of linguistic performance to linear structures given at the level of competence (for example Babyonyshev & Gibson 1999, Joshi 1990, Rambow & Joshi 1994, and Lewis & Nakayama 2001). Keeping in line with this tendency in research, this paper tries to reestablish the much discussed relationship between the two aspects of language, competence and performance: the issue of processing difficulty dependent on sorts of multiple clause embedding is addressed by incorporating into HPSG a mechanism reflecting left-to-right processing and memory costs calculated at each processing step. The organization of this paper is as follows. After delineating processing difficulty caused by multiply embedded clauses in Section 22.2, a short introduction to the psycholinguistic theory we rely on, the Syntactic Prediction Locality Theory, is provided in Section 22.3. Section 22.4 proposes an extension of the linearization-based version of HPSG to equip it with an architecture which evaluates sentence complexity. Then Section 22.5 illustrates how the mechanism copes with the difference in processing complexity between differently embedded rela-