Ambiguity in Japanese relative clause processing

Abstract In Japanese, relative clauses have initial clause-type ambiguity. Because there are no overt RC markers, the structure is realized at a locus of disambiguation, typically the head noun. While previous studies have attenuated this ambiguity, these studies have not effectively investigated the processing asymmetry between subject/object-relatives during reading. The current study investigated RC processing within different ambiguity contexts using eye-tracking on native Japanese speakers. For ambiguous RCs, ORC difficulties were primarily observed during late-processing measures after disambiguation at the head noun and RC verb. This was possibly due to the inherent difficulty of assigning thematic roles when the object appears outside the clause as the object-before-subject-bias predicts or due to factors such as expectation, structural-integration and similarity interference. Because all predict ORC difficulties in ambiguous RCs, the exact nature of the processing remains uncertain. For unambiguous RCs, ORC difficulties were instead observed during early-processing measures at the head noun. We attribute this to expectation-based processing because the clause no longer requires a structural reconfiguration. Specifically, with increased cues for the RC interpretation, expectation-based processing effects became more observable at the head. In conclusion, clause type ambiguity is an integral factor for Japanese relative clause processing.