Trans-EnV: A Framework for Evaluating the Linguistic Robustness of LLMs Against English Varieties
Paper · 2025 · Jiyoung Lee, Seungho Kim, Jieun Han et al.
Summary
LLM benchmarks are written almost entirely in Standard American English (SAE), so it is unclear how well models serve people who use regional dialects or write English as a second language (ESL). The authors built Trans-EnV, a pipeline that rewrites existing SAE benchmark items into a chosen English variety.
Linguistic features come from expert resources: eWAVE for dialects and the English Grammar Profile for learner English at CEFR levels A and B. For each feature, an LLM drafts a step-by-step transformation guideline. A feature transformer LLM then applies the variety's features one at a time, while a semantic checker LLM verifies that the meaning is preserved. Learner variants also reflect the writer's first language, and advanced vocabulary is first replaced with simpler wording.
Six benchmarks were converted into 38 varieties, and seven current LLMs were tested on them. Accuracy fell on most varieties, by up to 12.5% for dialects and 46.3% for ESL, and reasoning tasks were hit hardest. The framework makes robustness to English variation measurable at scale.
Key points
- Dialect selection: The 18 dialects were chosen from the 77 varieties in eWAVE, which documents 235 features and was compiled by 84 linguists from 175 publications. KNN clustering over the feature profiles separated English dialects from creoles and pidgins. Only features marked at the highest presence level define each dialect.
- ESL varieties: The 20 ESL varieties draw on the English Grammar Profile, which maps 1,222 "can-do" grammar features to CEFR levels. A lower level is simulated by stripping out constructions that belong to higher levels.
- Main results: Larger drops appear for L1s that are harder for English speakers to learn, such as Arabic, Chinese-Mandarin and Japanese, compared with easier L1 categories (shown on GSM8K and ARC). Models specialised for reasoning proved more robust.
- Open-ended tasks: IFEval, AlpacaFarm and MT-Bench were run on 8 dialects and 10 ESL variants with four models: Qwen2.5-72B-Instruct, DeepSeek-R1-Distill-Llama-70B, LLaMA-3.3-70B-Instruct and o4-mini. GPT-4.1 served as judge.
- CEFR B inputs scored above CEFR A inputs.
- Irish, Newfoundland and Welsh English scored below AAVE, Australian and Tristan da Cunha English.
- Validation and release: Transformation coverage exceeded 80%. The framework was checked through statistical tests, human evaluation, and ongoing advice from a second language acquisition researcher. Code is on GitHub and the datasets are on Hugging Face.
Interesting ideas
- I1. Variation is decomposed into a catalogue of expert-documented features, each with its own written rewrite procedure, applied one after another under a meaning-preservation check; this makes each change traceable instead of producing an opaque "dialect-ify" rewrite.
- I2. A lower proficiency level is defined subtractively, by removing constructions that the grammar profile assigns to higher levels; this gives a principled, checkable notion of "simpler text."
- I3. Because the transformations keep meaning fixed, any change in the answer is a robustness failure by construction; this is an invariance test that needs no new gold labels.
- I4. Results are grouped by how far a variety, or a learner's L1, sits from SAE, which turns scattered scores into a gradient that shows where robustness breaks down.
- I5. A lexical simplification pass runs before grammatical features are injected, so vocabulary and syntax effects can be studied separately.
For Mova
How these ideas could serve Mova, our small open language model — its files, stages and tests:
- I1 (learn): Build negative-control evaluation sets by applying single eWAVE features to clean sentences, then check that the parser and frame extractor yield the same who-did-what-to-whom as on the SAE original.
- I2 (back): Constrain generation or retelling to EGP constructions of a target CEFR level, so Mova can produce graded simplified versions of tales and explain which constructions it avoided.
- I3 (answer): Rerun school tests and fable QA on dialect and learner variants, then use Mova's explainable pipeline to locate which stage (tokens, tree, frames) diverged when an answer flips.
- I4 (tree): Report LAS per variety bucket ordered by distance from SAE, and prioritise UD dialect conversion or repair rules for high-impact features such as multiple negation or dropped copulas.
- I5 (tokens): Test the tagger and lemmatizer on vocabulary-simplified versus grammar-altered variants independently, to see whether errors come from unknown words or from non-standard morphosyntax.
Institutions
Fields, topics and concepts
📚 Shelves 4The field of science this work belongs to (OpenAlex fields).Computer Science · 16,667 worksArtificial Intelligence · 16,194 worksArts and Humanities · 16,039 worksLanguage and Linguistics · 15,891 works
🧭 Topics 3Research subjects and languages the work is about.Language models & pretraining · 3,320 worksEnglish · 2,263 worksGrammatical error correction & learner language · 156 works
Cite
Cite as Jiyoung Lee, Seungho Kim, Jieun Han, Jun-Min Lee, Kitaek Kim, Alice Oh and Edward Choi. 2025. Trans-EnV: A Framework for Evaluating the Linguistic Robustness of LLMs Against English Varieties. arXiv:2505.20875.
@misc{lee2025trans,
title = {{Trans-EnV: A Framework for Evaluating the Linguistic Robustness of LLMs Against English Varieties}},
author = {Jiyoung Lee, Seungho Kim, Jieun Han, Jun-Min Lee, Kitaek Kim, Alice Oh and Edward Choi},
year = {2025},
doi = {10.48550/arxiv.2505.20875},
eprint = {2505.20875},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.2505.20875}
}References
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