PCFGs with Syntactic and Prosodic Indicators of Speech Repairs

Proceedings of the 21st International Conference on Computational Linguistics and 44th Annual Meeting of the ACL, pages 161–168, Sydney, July 2006. c⃝2006 Association for Computational Linguistics PCFGs with Syntactic and Prosodic Indicators of Speech Repairs John Halea Izhak Shafranb Lisa Yungc Bonnie Dorrd Mary Harperde Anna Krasnyanskayaf Matthew Leaseg Yang Liuh Brian Roarki Matthew Snoverd Robin Stewartj a Michigan State University; b,c Johns Hopkins University; d University of Maryland, College Park; e Purdue University f UCLA; g Brown University; h University of Texas at Dallas; i Oregon Health & Sciences University; j Williams College Abstract A grammatical method of combining two kinds of speech repair cues is presented. One cue, prosodic disjuncture, is detected by a decision tree-based ensemble clas- sifier that uses acoustic cues to identify where normal prosody seems to be inter- rupted (Lickley, 1996). The other cue, syntactic parallelism, codifies the expec- tation that repairs continue a syntactic category that was left unfinished in the reparandum (Levelt, 1983). The two cues are combined in a Treebank PCFG whose states are split using a few simple tree transformations. Parsing performance on the Switchboard and Fisher corpora sug- gests that these two cues help to locate speech repairs in a synergistic way. 1 Introduction Speech repairs, as in example (1), are one kind of disfluent element that complicates any sort of syntax-sensitive processing of conversational speech. (1) and [ the first kind of invasion of ] the first type of privacy seemed invaded to me The problem is that the bracketed reparan- dum region (following the terminology of Shriberg (1994)) is approximately repeated as the speaker The authors are very grateful for Eugene Charniak’s help adapting his parser. We also thank the Center for Language and Speech processing at Johns Hopkins for hosting the sum- mer workshop where much of this work was done. This material is based upon work supported by the National Sci- ence Foundation (NSF) under Grant No. 0121285. Any opin- ions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. “repairs” what he or she has already uttered. This extra material renders the entire utterance ungrammatical—the string would not be gener- ated by a correct grammar of fluent English. In particular, attractive tools for natural language understanding systems, such as Treebank gram- mars for written corpora, naturally lack appropri- ate rules for analyzing these constructions. One possible response to this mismatch be- tween grammatical resources and the brute facts of disfluent speech is to make one look more like the other, for the purpose of parsing. In this separate-processing approach, reparanda are located through a variety of acoustic, lexical or string-based techniques, then excised before sub- mission to a parser (Stolcke and Shriberg, 1996; Heeman and Allen, 1999; Spilker et al., 2000; Johnson and Charniak, 2004). The resulting parse tree then has the reparandum re-attached in a standardized way (Charniak and Johnson, 2001). An alternative strategy, adopted in this paper, …

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