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<Paper uid="H92-1086">
  <Title>PROSODIC STRUCTURE, PERFORMANCE STRUCTURE AND PHRASE STRUCTURE</Title>
  <Section position="3" start_page="0" end_page="0" type="metho">
    <SectionTitle>
1. INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> It is natural to expect phrase structure to be important in predicting prosodic phrasing. Hence it is somewhat unsettling that the relationship between prosodic and syntactic structure appears so tenuous, as for example in Selkirk's account \[10, 11, 12\]. Selkirk's prosodic structure differs from standard phrase structure on several counts, but most notably because it is much flatter than standard phrase structure, which is heavily right-branching in English:</Paragraph>
    <Paragraph position="2"> The absem..minded pmfemm has beeo avidly m~ling sbom the lalesl bielpzphy of Man~ ~ In a similar vein, some psycholinguists have concluded that syntactic structure provides an inadequate model of the performance structures reflected in linguistic behavior. Martin, Grosjean, and others have explored experimental measures of the relative prominences of boundaries between words, and conclude that the syntactic prominence of a boundary is not the best predictor of its empirical prominence \[4, 6, 7, 8, 9\].</Paragraph>
    <Paragraph position="3"> If prosodic structures and performance structures differ from phrase structure, however, they appear to correspond well to each other. For example, Gee and Grosjean \[6\] use Selkirk's prosodic phrases in an algorithmic model of their experimental data. And turnabout being fair play, Bachenko and Fitzpatrick \[3\] adapt Gee and Grosjean's algorithm to predict prosodic structure for speech synthesis.</Paragraph>
    <Paragraph position="4"> However, I believe the perceived inadequacy of syntactic structure is at least in part an artifact of measures of syntactic boundary prominence that are based on immediate-constituency trees alone. I would like to show that we can obtain a measure of syntactic boundary prominence that corresponds better to prosodic and psycholinguistic boundary prominence if we view phrase structure as a composite of immediate constituency and dependency relations.</Paragraph>
  </Section>
  <Section position="4" start_page="0" end_page="425" type="metho">
    <SectionTitle>
2. CHUNKS AND DEPENDENCIES
</SectionTitle>
    <Paragraph position="0"> I propose that the structure relevant for prosody and performance is a composite of immediate-constituency and dependency relations. Usually, dependency grammar is an alternative for representing phrase structure, in competition with immediate constituency. However, there is often a systematic correspondence between dependencies and immediate constituency. I will assume such a correspondence, and define dependency in terms of immediate constituency, as follows: Y depends on X iff X is a word, and Y is an immediate constituent of a phrase headed by X Graphically: !  Dependencies are combined with immediate constituency in the relation is licensed by. X may license Y either by dependency or by immediate constituency:</Paragraph>
    <Paragraph position="2"> Y is an immediate constituent of X, and there is no node that licenses Y by dependency Consider, for example, the following sentence (adapted from \[10\]): the absent-minded professor from Princeton was reading a biography of Marcel Proust The major-category heads are absent-minded, professor, Princeton, reading, biography, Marcel Proust. The PP from Princeton follows, and depends on, professor; hence from Princeton is licensed by dependency. Likewise for a biography (depends on reading), and of Marcel Proust (depends on biography). These three phrases are licensed by dependency; all the other phrases are licensed by immediate constituency. We can represent the licensing structure as follows, where the arrows represent licensing by dependency, and the straight lines represent licensing by immediate constituency: S There is a certain similarity between this structure and Selkirk's prosodic structure. In particular, if we consider only the relation licenses by immediate constituency, and excise the clausal node (S), the remaining connected pieces of phrase structure--which I call chunks---are Selkirk's C-phrases. Gee and Grosjean also base their algorithm on C-phrases. The correspondence between chunks and C-phrases suggests that licensing structure might do better than standard phrase structure in predicting prosodic and performance-structure boundary prominence. 1 1 An analysis in which phrase structure consists of a series of strata--words, chunks, simplex clauses--also proves useful for</Paragraph>
  </Section>
  <Section position="5" start_page="425" end_page="426" type="metho">
    <SectionTitle>
3. MEASURING SYNTACTIC
BOUNDARY STRENGTH
</SectionTitle>
    <Paragraph position="0"> Given phrase structure trees, we also require a method for computing boundary prominence. The method that I take to be &amp;quot;standard&amp;quot; is the one assumed in the performance-structure literature, by which the prominence of a boundary b is the number of non-terminal nodes in the smallest constituent spanning b. For example: null</Paragraph>
    <Paragraph position="2"> I would like to propose an alternative measure. The  general idea is as follows: 1. Clause boundaries &gt; chunk boundaries &gt; word boundaries 2. &amp;quot;Strong&amp;quot; dependencies between immediately adjacent chunks/clauses weakens the boundary between them 3. Phonologically weak chunks &amp;quot;cliticize&amp;quot; to the adjacent chunk  Phonologically weak chunks are chunks containing a single word whose category is pronoun, particle, auxiliary, conjunction, or complementizer. The following are specific boundaries weakened by &amp;quot;cliticization&amp;quot;:  rapid, robust parsing of unrestricted text \[1, 5\]. The parsing advantages of chunks provided my original motivation for considering them. I undertook the work described here in order to make good on earlier hand-waving about a possible relation between chunks and prosodic phrases.</Paragraph>
    <Paragraph position="3">  I also relax the adjacency requirement to permit one intervening phonologically weak chunk. In particular, if a particle or indirect object pronoun intervenes between a verb and its following dependent, the boundary before the dependent is still weakened.</Paragraph>
    <Paragraph position="4"> I assign the following heuristic values to boundaries. What is important for my purposes is the relative values, not the absolute values.</Paragraph>
    <Paragraph position="5">  The top numbers are the boundary prominences according to the chunks-and-dependencies model; the bottom numbers (in italic) are empirical values obtained by Martin \[9\] in a naive-parsing experiment. The length of the vertical lines corresponds to the theoretical prominence of each boundary. The horizontal lines represent the locM relative prominence domain of each boundary: the solid lines according to the model, the dotted lines according to the data. In this case, the theoretical and empirical domains match exactly.</Paragraph>
    <Paragraph position="6"> This is the same sentence, using the standard model:</Paragraph>
    <Paragraph position="8"> The bold arrows mark dependencies that induce weakening. The first boundary is a clause boundary, weakened from 3 to 2. The second boundary is a chunk boundary. Since who is phonologically weak, the boundary is weakened to 0. The third boundary is a chunk boundary weakened from 2 to 1. The fourth boundary is an unweakened clause boundary, value 3. The next to last boundary is a weakened chunk boundary, and the final boundary is an unweakened chunk boundary.</Paragraph>
  </Section>
  <Section position="6" start_page="426" end_page="426" type="metho">
    <SectionTitle>
4. COMPARING THE MODELS
</SectionTitle>
    <Paragraph position="0"> To compare the chunks-and-dependencies model to the standard model, we need to compare both models to boundary-prominence data. I am primarily interested in the local relative prominence of boundaries. A boundary &amp;quot; b is defined to be locally more prominent than boundary c iff b is more prominent than c and every intervening boundary is less prominent than c. In comparing theoretical and empirical prominences, each inversion counts as an error. An inversion arises wherever b is locally more prominent than c according to the model, but c is locally more prominent than b according to the data.</Paragraph>
    <Paragraph position="1">  In this case, there is an inversion: the second boundary is more prominent than the third, according to the model, but the third is more prominent than the second, according to the data. The inversion is reflected in the line crossing.</Paragraph>
  </Section>
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