The interplay of free word order and pro-drop in incremental sentence processing: Neurophysiological evidence from Japanese

The present dissertation investigated the mechanisms of incremental sentence processing in Japanese, a language with word order freedom (scrambling) and argument omissibility (pro-drop). To this avail, four event-related brain potential (ERP) experiments were conducted employing simple transitive sentences, with Experiments 1 and 2 investigating the influence of prosodic information and case marking on the processing of scrambled sentences, and Experiments 3 and 4 examining the processing of pro-drop sentences in isolation and embedded in linguistic contexts. The neurophysiological data pattern observed across experiments strongly suggested the separation of a phrase structural, interpretive, and discourse level of representation, with a universal processing principle called Minimality applying at all three levels (requiring minimal one-argument structures, minimal intransitive events with only one participant, and minimal discourse representations without redundant referents, respectively). Crucially, depending on the level of representation, violations of the Minimality principle were reflected in different kinds of independently varying ERP signatures: A one-argument phrase structure could not be maintained whenever an initial object signaled a scrambled (OSV) sentence, engendering a scrambling negativity in comparison to initial subjects as a result. If, however, the prosodic information or the case marking on the initial object allowed an alternative one-argument (subject-drop, OV) reading of the sentence, no such effect was observable. Regardless of prosodic or case marking information, an N400 always arose at the position of the second argument of canonical (SOV) sentences in comparison to scrambled (OSV) sentences, reflecting the extension from an intransitive to a transitive event interpretation that became necessary at this position. Finally, at the discourse level, Minimality effects became evident in the variations of a positivity effect arising at the position of the verb of subject-drop (OV) and object-drop (SV) sentences in comparison to canonical complete (SOV) sentences. This component, which was taken to reflect the inference of the missing discourse referent from outside the sentence, was particularly pronounced when a new discourse referent needed to be established, i.e. when the pro-drop sentence was presented in isolation or when the preceding context did not provide a suitable referent. An additional sensitivity of the positivity effect to the amount of referential competition further supported a conceptualization of Minimality as a subcase of a more general processing principle calling for maximally distinct representations at all three levels. In sum, the present findings suggest that a Minimality/Distinctness based account incorporating several levels of representation qualifies as a promising approach to deriving the neurocognitive signatures of incremental sentence comprehension across languages