LongEval: Guidelines for Human Evaluation of Faithfulness in Long-form Summarization
Summary
Human judgment is still the most trusted way to check whether a generated summary is faithful to its source. For summaries of 150+ words, however, such checks are costly, slow and inconsistent. The authors surveyed 162 papers that use long-form summarization datasets. Most never asked humans to rate long outputs, and the rest used ad-hoc setups that are hard to reproduce. In response, they propose LongEval, three guidelines for faithfulness evaluation, and test them with expert annotators on SQuALITY (fiction) and PubMed (biomedical).
Their findings:
- Judging small units such as clauses and averaging the results gives far more consistent scores than a single Likert rating per summary.
- Annotating only a sample of these units gives nearly the same scores as annotating all of them.
- Automatically linking summary parts to source sentences helps only when summaries are very extractive or largely accurate.
The work offers practical evidence for cheaper and more reliable evaluation of long outputs. The authors also release judgments that can serve as a benchmark for automatic metrics.
Key points
- Survey of 162 papers (2018–2022): 73% do not evaluate long-form summaries with humans (62% no human evaluation at all, 11% short summaries only). Of the 44 papers that do, only 2 release raw annotations and 12 report inter-annotator agreement.
- Granularity: Moving from coarse Likert scores to fine-grained clause judgments reduced the standard deviation of faithfulness scores on SQuALITY from 18.5 to 6.8.
- Partial annotation: Annotating half of the fine-grained units still produced scores with 0.89 Kendall's τ against the full annotation.
- Alignment hints: Highlighting relevant source sentences was of limited value. This contrasts with earlier recommendations from short-form summarization research.
- Released resources: 3-way fine-grained faithfulness judgments for 120 SQuALITY and PubMed summaries, plus annotation templates and code (github.com/martiansideofthemoon/longeval-summarization).
Cited by
- FActScore: Fine-grained Atomic Evaluation of Factual Precision in Long Form Text Generation
- Assisting in Writing Wikipedia-like Articles From Scratch with Large Language Models
- Fine-Grained Human Feedback Gives Better Rewards for Language Model Training
Cite
@inproceedings{krishna2023longeval,
title = {{LongEval: Guidelines for Human Evaluation of Faithfulness in Long-form Summarization}},
author = {Krishna, Kalpesh and Bransom, Erin and Kuehl, Bailey and Iyyer, Mohit and Dasigi, Pradeep and Cohan, Arman and Lo, Kyle},
booktitle = {Proceedings of the 17th Conference of the European Chapter of the Association for Computational Linguistics},
year = {2023},
doi = {10.18653/v1/2023.eacl-main.121},
url = {https://doi.org/10.18653/v1/2023.eacl-main.121}
}References
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