How grammatical and discourse factors may predict the forward prominence of referents: two corpus studies.

One of the ways in which discourse coheres is by means of repeated reference to entities. Theoretical accounts of referential coherence propose heuristics for the interpretation of referential expressions, which are especially important when there is more than one potential antecedent. One of the most explicit accounts is provided by Centering Theory (Grosz et al., Computational Linguistics 21: 203–225, 1995). Using features such as grammatical status, expression type, and the referential relation with sentences still further back in the discourse, it produces a ranking of discourse referents in terms of forward prominence. We present two corpus studies of how these features, in combination with discourse topichood, help to predict referential continuations in actual discourse. In Study 1, we analyzed newspaper fragments in which he is preceded by a sentence presenting two male singular participants. The factors Grammatical Role (being a Subject), Backward Center Status and Discourse Topichood appear to increase the chance that a referent is the intended one for a potentially ambiguous pronoun, while Expression Type (noun or pronoun) makes no difference. In Study 2, the continuations for sentences with two referents differing on the same four factors were compared, assuming that the most prominent referent will reappear in the next sentence. The study reveals that Grammatical Role only affects the form of continuation: subject referents do not reappear more often, but when reappearing they are more often realized as pronouns. Backward Center Status increases the chance of subsequent references to a referent, and also decreases the chances for its competitor of being referred to again. Discourse Topichood has the same double effect. In conclusion, both global and local factors affect referential prominence, but in different ways.