Presuppositions in Spoken Discourse

Between Binding and Accommodation
also restrict the potential search space, though they point out that they are unsure
as to whether or not Clark’s original taxonomy covers all the different coherence
relationships that are out there, and that we might need to identify. The third metarule
is Discourse Structure Determines Bridging, and says that if there is a
rhetorical relationship that can be identified by using information about a possible
bridging inference, then that inference should be made. This would seem to make
determining rhetorical structure prior to bridging, though in other cases bridging
helps to determine discourse structure. This may not be an absolute rule.
Finally, the fourth meta-rule is Maximize Discourse Coherence and this
rule makes creating the most coherent discourse structure primary to world or
lexical knowledge in resolution, sometime overriding it. The following example is
taken from Matsui (1995). It illustrates how discourse structural needs can override
world knowledge.
(8) John moved from Brixton to St. Johns’ Wood. The rent was less expensive. 6
World knowledge tells us that rents in Brixton are generally cheaper than rents in
St. John’s Wood. This would lead to a conclusion that the rent must be less
expensive in Brixton, and the bridging NP the rent should be resolved to Brixton.
But this results in a less coherent discourse because it is then difficult to understand
the relationship between the two sentences. Why did John move? Asher &
Lascarides argue that interpreters prefer to find explanations that make agents’
actions intentional. If St. John’s Wood is considered to be the anchor instead, then
a rhetorical relation of Explanation can be calculated between the two sentences,
and this is preferred. Therefore, despite world knowledge to the contrary, we prefer
to interpret the anchor as St. John’s Wood because it lets us understand the
coherence between the two sentences. Note that cases where there are several
anchors that will lead to different interpretations are the types of examples in
particular where the link needs to be determined in order to choose between
competing anchors.
Asher & Lascarides’ proposal would seem to be able to handle a larger
subset of examples than a pure lexical or encyclopedic approach. However, even
though their examples purport to take a more discourse-oriented perspective, they,
like most work on bridging, generally confine their analysis to two sentence
sequences, where the anchor is in the first sentence and the bridging anaphor
appears in the second. Natural language examples will probably reveal cases where
there are bridging relationships over much greater distances, and where it may be
difficult to find a rhetorical relationship of the kind they have envisioned, or the
bridging relationship itself may not be as crucial to the discourse structure as in the
examples with which they have chosen to illustrate their approach.
6 Example taken from Wilson & Matsui (1998), but originally from Matsui (1995).
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