Annotating and Modeling Fine-grained Factuality in Summarization
Written for the Research library (claude-opus-5-5) from the paper text. Original — aclanthology.org/2021.naacl-main.114.pdf
Summary
Abstractive summarizers often produce statements the source document does not support. It has been unclear which kinds of errors matter most and whether current factuality detectors catch them. Goyal and Durrett compare three ways to get training data for factuality classifiers on two English news domains, XSum and CNN/DailyMail. These are entity-centric synthetic corruptions (Ent-C, following Kryscinski et al., 2020), generation-centric paraphrase data (Gen-C), and human-labeled model summaries. To compare them fairly, the authors align supervision at the sentence, dependency-arc and word levels, deriving arc labels from highlighted error spans. Error profiles differ sharply between the two domains. Rule-based corruptions also poorly match the mistakes real models make on the highly abstractive XSum data. Fine-grained human annotation gives the strongest training signal: it lets the dependency-arc entailment (DAE) model detect and locate errors better than sentence-level or synthetic supervision. As a practical use, the DAE model flags non-factual tokens in noisy reference summaries so they can be excluded from the training loss. The resulting BART summarizer is noticeably more faithful.
Key points
- Synthetic data: about 50k Ent-C pairs per domain, built with entity, number and pronoun swaps, negation, noise injection and backtranslation. Gen-C provides 40k examples per domain, using 10th-best paraphrases from the Goyal and Durrett (2020b) model.
- An arc counts as non-factual if its head or child word falls inside a highlighted error span. Word-level decisions can be recovered from arc predictions.
- On XSum, the DAE model trained on fine-grained human labels localizes errors better than DAE-Weak at both the arc and word level.
- The authors mask DAE-flagged tokens out of the log-likelihood loss when training BART (initialized from BART-XSUM-LARGE, 50k examples). Compared with a standard baseline and loss truncation, this cuts the word error rate from 32.2 (baseline) and 31.1 (loss truncation) to 23.7. The sentence error rate falls from 74.0 and 70.9 to 61.4.
- In a Mechanical Turk evaluation, 7 annotators each judged summaries for 50 articles. Factuality scores were 46.5 for the masked model, versus 37.4 for the baseline and 39.1 for loss truncation. Code and data are released at github.com/tagoyal/factuality-datasets.
Cited by
- CLIFF: Contrastive Learning for Improving Faithfulness and Factuality in Abstractive Summarization
- RARR: Researching and Revising What Language Models Say, Using Language Models
- Evaluating Large Language Models: A Comprehensive Survey
- A Survey on Hallucination in Large Language Models: Principles, Taxonomy, Challenges, and Open Questions
- Trusting Your Evidence: Hallucinate Less with Context-aware Decoding
- MiniCheck: Efficient Fact-Checking of LLMs on Grounding Documents
Cite
@inproceedings{goyal2021annotating,
title = {{Annotating and Modeling Fine-grained Factuality in Summarization}},
author = {Goyal, Tanya and Durrett, Greg},
booktitle = {Proceedings of the 2021 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies},
year = {2021},
doi = {10.18653/v1/2021.naacl-main.114},
url = {https://doi.org/10.18653/v1/2021.naacl-main.114}
}References
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