Dialogue act modeling for automatic tagging and recognition of conversational speech
Andreas StolckeKlaus RiesNoah CoccaroElizabeth ShribergRebecca BatesDaniel JurafskyPaul TaylorRachel MartinCarol Van Ess-DykemaMarie Meteer
Develops a probabilistic framework combining discourse grammar, acoustic prosody, and word n-grams to automatically classify dialogue acts and improve conversational speech recognition on the Switchboard corpus.
This paper develops a statistical framework for automatically tagging and recognizing dialogue acts—such as statements, questions, backchannels, agreements, and apologies—in spontaneous conversational telephone speech. The work addresses the challenge of modeling discourse structure to support higher-level applications like meeting summarization and conversational agents, while also feeding constraints back to improve automatic speech recognition. The authors treat sequences of dialogue acts as a hidden Markov model whose states emit observations derived from words and prosody, and they integrate this with n-gram discourse grammars, word-based language models, decision trees, and neural networks.
They trained and evaluated the models on 1,155 hand-labeled Switchboard conversations comprising roughly 205,000 utterances. The framework was tested both with perfect word transcripts and with the output of a speech recognizer that had a 41% word error rate, and it incorporated prosodic features such as duration, pitch, and energy extracted directly from the waveform.
The combined model achieved 71% dialogue-act labeling accuracy on word transcripts and 65% accuracy when driven by recognizer output, compared with a 35% chance baseline and 84% human interlabeler agreement. Adding prosody produced consistent gains, especially on ambiguous distinctions such as backchannels versus agreements and questions versus statements; the largest relative benefit appeared when word information was imperfect. The same models yielded a small but statistically reliable reduction in word error rate during speech recognition rescoring, with the greatest improvements on short, lexically constrained acts such as answers and backchannels. Bigram discourse grammars proved nearly optimal, and alternative modeling choices such as maximum-entropy or neural-network discourse grammars added little.
These results demonstrate that a unified probabilistic treatment of lexical, prosodic, and sequential cues can extract useful discourse information from large quantities of noisy conversational data and can modestly tighten language-model constraints for recognition. The gains are limited by the heavy skew toward statements in the Switchboard domain; task-oriented dialogues with more balanced act distributions would likely see larger recognition benefits. The main limitations are the assumption of pre-segmented utterances and the conditional-independence assumptions that decouple evidence across turns and across knowledge sources.
Future work should explore joint lexical-prosodic models that relax those independence assumptions, incorporate turn-overlap timing, and investigate unsupervised discovery of dialogue-act categories optimized for the primary downstream task.
- Paper: Word Association Norms, Mutual Information, and Lexicography, Kenneth Ward Church et al. (1989). Reading this foundational paper on mutual information and lexical associations helps understand the statistical word-association metrics that underpin lexical dialogue act modeling.
- Paper: Conformer: Convolution-augmented Transformer for Speech Recognition, Anmol Gulati et al. (2020). This paper extends speech recognition modeling by introducing advanced convolutional architectures and data augmentation techniques that improve upon earlier statistical speech pipelines.
