| This research investigates the processing difficulty associated with double center-embedding in Japanese, and the effect of three consecutive subject NPs identically marked with the nominative particle-ga offers the means to explore the mechanisms underlying the problem. Three interrelated experiments focus on structural manipulations.; Psycholinguists argue that the human sentence processing system is highly efficient, but that its resources have limits. The observation that fully grammatical double-embeddings such as "The rat the cat the dog chased ate died" (Chomsky & Miller 1963: 286) are unprocessable---as two-level center-embeddings are claimed to be, in general---is therefore viewed as a realization of the competence-performance distinction. Many explanations have been proposed, but just why these structures are problematic remains unresolved after half a century. Exploiting structural characteristics of Japanese, this study adds to the body of available information, previously drawn mainly from studies of English.; Experiment 1 utilized two off-line processability rating tasks. The results suggest that processability improves in both single- and double-embeddings, whenever a sequence of three consecutive NP-ga's is reduced or interrupted by a structural manipulation.; Experiment 2 employed a self-paced reading method and an experimental design devised to isolate any cost engendered by three consecutive NP -ga's. The results show that detectable costs exist only in double center-embedding, suggesting that the parser has difficulty making identical structural assignments, repeatedly, for surface-adjacent constituents. Identity and adjacency factors also explain English embeddings of varying kinds.; Experiment 3 used an off-line sentence completion task to explore the impact of an ambiguity associated with NP-ga, given its multiple syntactic functions: -ga case-marks single subjects, parallel subjects, nominative objects, and external possessors. While it is agreed that the English double center-embedding problem is unrelated to ambiguity, the situation is a priori less clear in Japanese. This study shows, for the first time, that NP-ga is interpreted with high probability as a single subject, suggesting that it is effectively unambiguous when encountered in Japanese double-embeddings. Detailed analyses of the sentence completion database illustrate the intersection of NP -ga's syntactic roles and universal processing principles, lending support to the claim that the parser is not parameterized. |
