Argument structure affects relative clause extraposition: corpus evidence from Persian

The extraposition of a relative clause creates a discontinuous dependency between the relative clause and its host noun phrase, as in A man just entered the bank who claimed to have a gun. Since discontinuous dependencies are known to increase processing effort, a key question is why speakers produce them in the first place. Some factors known to affect extraposition – for example, the length of the relative clause and the main verb phrase – have received processing-based explanations, but others haven’t. We focus on two factors described by previous research: verb type and the grammatical function of the noun phrase hosting the relative clause. Specifically, extraposition from grammatical subjects is more common with unaccusative and passive verbs in English; further, extraposition is more common from grammatical objects than subjects in Dutch and German. We replicate these findings using corpus data from Persian. Further, we propose that verb type and grammatical function can be linked to a single underlying notion: argument structure. We demonstrate that argument structure modulates the likelihood of extraposition in Persian. We suggest that this occurs because speakers choose to extrapose relative clauses in order to keep the main clause verb close to its internal arguments. This explanation extends previous findings in psycholinguistics on the role of argument structure in speech planning during language production.