ID10M-JAM: Stress-Testing Idiom Identification Under Challenging Context
Summary
LLMs score well on idiom identification benchmarks, but it is unclear whether they stay accurate when the surrounding text pushes toward the wrong reading. The authors built ID10M-JAM, an adversarial version of the English and German test portions of ID10M. For each sentence containing a potential idiomatic expression (PIE), they prepended a fluent, coherent context that favours the opposite interpretation: literal-sounding cues before figurative uses, and figurative-sounding cues before literal ones. Candidate variants were generated with LLM assistance, then filtered and refined by human annotators so that each stays natural and has one clear reading for people. The task is framed as BIO sequence labeling with no list of candidate expressions provided. They tested open-weight, closed-weight and reasoning models under zero-shot and more advanced prompting. Human annotators remained largely accurate, while models made many errors. Better prompting, larger scale and explicit reasoning improved overall identification but did not make models reliably more robust to the misleading context. The benchmark therefore exposes weaknesses that clean test sets hide.
Key points
- The source is the ID10M benchmark (Tedeschi et al., 2022), using 200 test sentences per language for EN and DE. ID10M's training sets contain 37,919 (EN) and 24,126 (DE) sentences. Italian and Spanish are left for future work.
- Labels follow the B-IDIOM / I-IDIOM / O tagging scheme. Models must find idiom spans and also decide whether each use is figurative or literal.
- In the human evaluation, two annotators reached 90.4% and 87.1% accuracy on the adversarial variants. Both found literal uses harder and tended to mark unclear items as ambiguous.
- The main finding is that identification accuracy and robustness to adversarial context are not coupled. Sophisticated prompting does not reduce susceptibility to misleading context.
- The data is released under CC BY-NC-SA 4.0 and the code under Apache-2.0 (github.com/Intellexus-DSI/ID10M-JAM). Because of budget limits, the cheaper models were run with three seeds and the expensive ones with a single seed.
Cite
@inproceedings{hashiloni2026id10m,
title = {{ID10M-JAM: Stress-Testing Idiom Identification Under Challenging Context}},
author = {Hashiloni, Kai Golan and Livyatan, Lior and Hefetz, Ofri and Mannor, Alon and Cohen, Bar and Bar, Kfir},
booktitle = {Findings of the Association for Computational Linguistics: ACL 2026},
year = {2026},
doi = {10.18653/v1/2026.findings-acl.1045},
url = {https://doi.org/10.18653/v1/2026.findings-acl.1045}
}References
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