Prosodic Structure, Performance Structure and Phrase Structure

PROSODIC STRUCTURE, PERFORMANCE STRUCTURE AND PHRASE STRUCTURE Steven Abney Bell Communications Research 445 South St., Morristown, NJ 07962-1910 ABSTRACT It is natural to expect phrase structure to be important in predicting prosodic phrasing. Yet there appears to be a concensus that syntactic phrases do not correspond well to prosodic phrasing, and independent structures have been pro- posed to account for prosody. I propose that the problem with phrase structure lies with the particular measures of boundary strength applied to syn- tactic structures, and with the fact that phrase structure is viewed as an immediate constituency tree exclusively. I pro- pose viewing phrase structure as a composite of immediate constituency and dependency relations, and present an alter- native measure of boundary strength. I show that boundary strength according to this measure corresponds much more closely to empirical prosodic (and psycholinguistic) boundary strength than does syntactic boundary strength according to a standard measure. 1. INTRODUCTION It is natural to expect phrase structure to be impor- tant in predicting prosodic phrasing. Hence it is some- what unsettling that the relationship between prosodic and syntactic structure appears so tenuous, as for exam- ple in Selkirk's account [10, 11, 12]. Selkirk's prosodic structure differs from standard phrase structure on sev- eral counts, but most notably because it is much flatter than standard phrase structure, which is heavily right- branching in English: U I ! I I l I I I t f I I I 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 behav- ior. Martin, Grosjean, and others have explored exper- imental measures of the relative prominences of bound- aries 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]. If prosodic structures and performance structures differ from phrase structure, however, they appear to corre- spond well to each other. For example, Gee and Gros- jean [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. However, I believe the perceived inadequacy of syn- tactic structure is at least in part an artifact of mea- sures 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 bound- ary prominence that corresponds better to prosodic and psycholinguistic boundary prominence if we view phrase structure as a composite of immediate constituency and dependency relations. 2. CHUNKS AND DEPENDENCIES I propose that the structure relevant for prosody and performance is a composite of immediate-constituency and dependency relations. Usually, dependency gram- mar is an alternative for representing phrase structure, in competition with immediate constituency. However, there is often a systematic correspondence between de- pendencies and immediate constituency. …

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