Centering: A Parametric Theory and Its Instantiations

Centering Theory is the best known conceptual framework for theorizing about local coherence and salience; however, its claims are articulated in terms of notions which are only partially specified, such as ‘previous utterance’, ‘realization’, or ‘ranking’, and can be viewed as PARAMETERS of the theory. A great deal of research has been concerned with providing more detailed specifications for these parameters; as a result, a large number of instantiations of Centering are possible. Our first goal was to investigate in a systematic fashion the effect of these different ways of setting the parameters on the theory’s claims. In order to do this, it was necessary to clarify what the theory’s claims are (one of our conclusions being that what has become known as ’Constraint 1’ is actually a central claim of the theory) and to clearly identify all of its parametric aspects (we argue that the notion of ‘pronoun’ used in Rule 1 has to be considered a parameter). We found that while the theory’s main claim about salience and pronominalization, Rule 1, is verified with most ways of setting the parameters, Constraint 1–a claim about (entity) coherence and CB uniqueness–is much more instantiation-dependent: it is not verified if the parameters are instantiated according to very mainstream views (‘Vanilla instantiation’), it only holds if indirect realization is allowed, and is violated by between 20 and 25% of utterances even with the most favorable instantiations. We also found a tradeoff between Rule 1, on the one hand, and Constraint 1 and Rule 2, on the other: setting the parameters to minimize the violations of local coherence leads to increased violations of salience, and viceversa. Our results suggest that continuous reference to the same entities cannot be the only criterion which makes discourses locally coherent; ‘entity’ coherence must be supplemented with an account of relational coherence.