Better Rewards Yield Better Summaries: Learning to Summarise Without References
Paper · 2019 · Florian Böhm, Yang Gao, Christian M. Meyer et al.
Summary
RL-based summarisers usually optimise ROUGE. ROUGE ranks whole systems reasonably well, but it is weak at telling a strong individual summary from a mediocre one, and it needs reference summaries. The authors replace it with a reward learned directly from human judgements. They use the ratings collected by Chaganty et al. (2018) for 2,500 summaries of 500 CNN/DailyMail news articles. They frame reward learning as either regression or preference learning and test several text encoders and neural architectures. The resulting reward model sees only the source document and the candidate summary, so no references are needed once it is trained. The learned reward agrees with human ratings significantly better than ROUGE, BLEU, METEOR, embedding-similarity metrics and a feature-based baseline. It was used to train an extractive system (NeuralTD) and an abstractive one (ExtAbsRL). In both cases human evaluators preferred the outputs over ROUGE-trained and state-of-the-art systems, even though ROUGE scores dropped. The work shows that a modest amount of human feedback can guide summarisers more effectively than large reference corpora.
Key points
- Data: each article has five summaries: outputs from See et al.'s seq2seq and pointer models, Paulus et al.'s ml and ml+rl models, plus the reference. Five crowd workers rated each one on a −1 to 1 scale.
- Correlation study: all metrics tested correlate poorly with humans at summary level, with G-Pre and G-Rec below .50. These metrics are ROUGE variants, BLEU-1–5, METEOR, InferSent-Cosine and BERT-Cosine.
- Extractive result: NeuralTD trained with the learned reward received significantly higher human ratings (p = 0.0057 in the reported comparison).
- Abstractive result:
- In a 20-document, three-rater evaluation, ExtAbsRL with the learned reward was rated higher than with ROUGE-L.
- Summaries with redundant sentences fell from six to two.
- Data efficiency and availability:
- The reward comes from about 2,500 ratings, compared with the ~287k document-reference pairs used by competing systems.
- Code and the learned reward are available at github.com/yg211/summary-reward-no-reference.
Institutions
📚 Shelves 4The field of science this work belongs to (OpenAlex fields).Computer Science · 9,086 worksArtificial Intelligence · 8,889 worksArts and Humanities · 9,296 worksLanguage and Linguistics · 9,206 works
Cite
Cite as Florian Böhm, Yang Gao, Christian M. Meyer, Ori Shapira, Ido Dagan and Iryna Gurevych. 2019. Better Rewards Yield Better Summaries: Learning to Summarise Without References. Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing and the 9th International Joint Conference on Natural Language Processing (EMNLP-IJCNLP).
@inproceedings{bohm2019better,
title = {{Better Rewards Yield Better Summaries: Learning to Summarise Without References}},
author = {Florian Böhm, Yang Gao, Christian M. Meyer, Ori Shapira, Ido Dagan and Iryna Gurevych},
booktitle = {Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing and the 9th International Joint Conference on Natural Language Processing (EMNLP-IJCNLP)},
year = {2019},
doi = {10.18653/v1/d19-1307},
url = {https://doi.org/10.18653/v1/d19-1307}
}References
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