Discourse structure and relative clause processing.

Studies in several languages have shown that subject-relative clauses are easier to process than object-relative clauses. Mak, Vonk, and Schriefers (2006) have proposed the topichood hypothesis to account for the preference for subject-relative clauses. This hypothesis claims that the entity in the relative clause that is most topicworthy will be chosen as the subject. By default, the antecedent of the relative clause will be chosen as the subject of the relative clause, because it is the topic of the relative clause. However, when the noun phrase (NP) in the relative clause is also topicworthy, the preference for the antecedent to be the subject will disappear. This was confirmed in two experiments. In Experiment 1, we tested relative clauses with a personal pronoun in the relative clause. We obtained a preference for object-relative clauses, in line with the assumption that personal pronouns refer to a discourse topic and are thus topicworthy. In Experiment 2, the discourse status of the NP in the relative clause was manipulated; either it was not present in the preceding context, or it was the discourse topic. The experiment showed that when the NP in the relative clause refers to the discourse topic, the difficulty of object-relative clauses is reduced, in comparison with relative clauses with an NP that is new in the discourse, even in the absence of any explicit cue in the relative clause itself. The experiments show that discourse factors guide processing at the sentence level.