Understanding Neural Abstractive Summarization Models via Uncertainty

Jiacheng Xu, Shrey Desai, Greg Durrett


Abstract
An advantage of seq2seq abstractive summarization models is that they generate text in a free-form manner, but this flexibility makes it difficult to interpret model behavior. In this work, we analyze summarization decoders in both blackbox and whitebox ways by studying on the entropy, or uncertainty, of the model’s token-level predictions. For two strong pre-trained models, PEGASUS and BART on two summarization datasets, we find a strong correlation between low prediction entropy and where the model copies tokens rather than generating novel text. The decoder’s uncertainty also connects to factors like sentence position and syntactic distance between adjacent pairs of tokens, giving a sense of what factors make a context particularly selective for the model’s next output token. Finally, we study the relationship of decoder uncertainty and attention behavior to understand how attention gives rise to these observed effects in the model. We show that uncertainty is a useful perspective for analyzing summarization and text generation models more broadly.
Anthology ID:
2020.emnlp-main.508
Volume:
Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing (EMNLP)
Month:
November
Year:
2020
Address:
Online
Editors:
Bonnie Webber, Trevor Cohn, Yulan He, Yang Liu
Venue:
EMNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
6275–6281
Language:
URL:
https://aclanthology.org/2020.emnlp-main.508
DOI:
10.18653/v1/2020.emnlp-main.508
Bibkey:
Cite (ACL):
Jiacheng Xu, Shrey Desai, and Greg Durrett. 2020. Understanding Neural Abstractive Summarization Models via Uncertainty. In Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing (EMNLP), pages 6275–6281, Online. Association for Computational Linguistics.
Cite (Informal):
Understanding Neural Abstractive Summarization Models via Uncertainty (Xu et al., EMNLP 2020)
Copy Citation:
PDF:
https://aclanthology.org/2020.emnlp-main.508.pdf
Video:
 https://slideslive.com/38939166
Code
 jiacheng-xu/text-sum-uncertainty