Centering Theory in natural text: a large-scale corpus study

We present an extensive corpus study of Centering Theory (CT), examining how adequately CT models coherence in a large body of natural text. A novel analysis of transition bigrams provides strong empirical support for several CT-related linguistic claims which so far have been investigated only on various small data sets. The study also reveals genre-based differences in texts’ degrees of entity coherence. Previous work has shown unsupervised CTbased coherence metrics to be unable to outperform a simple baseline. We identify two reasons: 1) these metrics assume that some transition types are more coherent and that they occur more frequently than others, but in our corpus the latter is not the case; and 2) the original sentence order of a document and a random permutation of its sentences differ mostly in the fraction of entity-sharing sentence pairs, exactly the factor measured by the baseline.