The optimization of conversational coherence
Date
2018-07-03
Authors
Black, Alexander Kenneth
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Abstract
Coherence and incoherence in conversation refer to the
relationship between adjacent parts of the conversation
(e.g., between one statement and the next, or between one
topic and the next). A clear, relevant connection is called
coherent; the absence of an obvious connection is
incoherent. Coherence and incoherence are therefore central
to any analysis of discourse, but, despite many existing
theories of coherence and incoherence, there is little
empirical knowledge of these phenomena.
This dissertation continues the study of coherence
began in my master's thesis. In it I propose three axioms
to describe the structure of coherence throughout
conversations:
I. Both coherence and incoherence are necessary for
conversation to occur.
II. Conversations optimize coherence both globally and
locally.
III. Coherence is optimized at several different,
hierarchical levels of conversation.
Because there is already evidence that coherence is
maximized at a global level (Black, 1986/1988), I chose to
test whether coherence is optimized at a local level.
Specifically, local optimization of sequential coherence
relations would consist of a series of alternations between
coherence and incoherence. I also sought to test this
hypothesis at several different levels of conversation
(statement, topic, and macrotopic).
In order to test the hypothesis, it was necessary to
develop a method for segmenting conversations into
statements, topics, and macrotopics and a method for
measuring the degree of coherence between these segments.
Using the guidelines developed, two judges were able to
segment conversations at all three levels with high
reliability. Similarly, other sets of raters used a
magnitude estimation procedure to scale the degree of
coherence between units at each of these levels and again
achieved high reliability.
It was also necessary to develop a time-series analytic
technique for verifying the predicted series of alternations
in short sequences of data, because existing methods are not
applicable to small Ns. The new statistic is based on the
geometric properties of a particular data set: it compares
the obtained sum of the interior angles facing toward the
mean of the data series with the sum of the interior angles
facing the mean of all other permutations of these data
points.
Three getting-acquainted conversations were obtained;
these yielded 325 statements (the spoken equivalent of a
sentence). After segmentation, coherence scaling, and
application of the optimization statistic, there was
moderate support for the hypothesis of local optimization.
Three quarters of the topics contained sequences of
propositions with a sum of interior angles that was smaller
than the sum of half of the alternative permutations. At
the macrotopic level, however, the hypothesis was not
supported.
The contributions of this dissertation are (1) an
explicit, parsimonious, discourse-based theory of coherence;
(2) objective methods for measuring and studying coherence;
and (3) a new time-series statistic; and (4) encouraging but
not yet convincing evidence for the theory.
Description
Keywords
Cohesion (Linguistics), Conversation, Discourse analysis