Presuppositions in Spoken Discourse

Chapter 6
Can current proposals be modified to deal with multiple anchors? The lexical
approach is seemingly easily modified to handle multiple anchors, but prerequisites
that the bridging NP be lexically linked to all its anchors. Modifying the
functionally based approaches is more difficult. If some bridging anaphors have
more than one anchor, and therefore more than one link, this certainly complicates
the task of determining how they function in a rhetorical relation. Asher &
Lascarides’ solution seems to, in some cases, require that there only be one possible
anchor and link because the relationship is a central part of the rhetorical structure
and would have to be modified to deal with these kind of examples. Note that the
examples Asher & Lascarides (1998a) choose to illustrate in their article are all
examples where the bridging inference and the discourse structure are intimately
related, which is probably not always the case.
I believe the multiple anchors are telling us something fundamental about
bridging. Bridging examples are related to and licensed by the context in which they
appear, and not by some unique individual in the context. This is a conclusion that
is difficult to reach if you only examine individual examples with a one or two
sentence context, and that is why I think the examples that we are most familiar
with are actually very misleading. Cases where there seems to be only a single
anchor and the bridging examples seem to be related only to this simple semantic
individual, are merely the product of a very poor context and are a special case that
I think are actually quite difficult to find in naturally produced discourse. Some of
the cases of a bridging NP that is licensed by only one other individual should
perhaps more appropriately be treated as discourse-new rather than as being
inferable.
Can current proposals be modified to deal with the overgeneration problem?
This problem is much more tricky, in that it is not at all clear what underlines the
perception of certain information as related to the text, while other information is
perceived as new. Individual differences probably play a large role in the perception
of something as new or related, and this was seen in the annotation data. However,
clear part-of relationships often lead to definite NPs being considered bridging
rather than perceived as completely new, but this is only one pattern. Here we need
more data to make any substantial generalizations.
There is one simple way to remedy the overgeneration problem in the
recognition of bridging NPs. A number of subgroups can be removed from the
original definition of bridging. It seems more helpful to see Clark’s original
inventory of relationships as an incomplete list of things that make discourse
coherent and connected, and not as a group that is necessarily optimally resolved
by using the same methods. Because the inventory includes co-reference,
pronominal reference as well as non-presuppositional items, basically all textual
relationships fall into the category of bridging. They differ in their semantic
characteristics to such a degree that they are better treated with different methods.
But to be fair, in most discussions of bridging (with Asher & Lascarides 1998a as a
notable exception) these groups are seldom discussed, with good reason. If all
textual relationships are bridging, bridging is no longer a useful concept.
176