🇦🇹 Paper accepted at ACL 2025: Right Answer, Wrong Score
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Our paper, Right Answer, Wrong Score: Uncovering the Inconsistencies of LLM Evaluation in Multiple-Choice Question Answering, has been accepted at ACL Findings 2025!
👏 Huge thanks to my co-authors Francesco Maria Molfese, Luca Moroni, Alessandro Scirè, Simone Conia and Roberto Navigli.
Abstract
One of the most widely used tasks for evaluating Large Language Models (LLMs) is Multiple-Choice Question Answering (MCQA). While open-ended question answering tasks are more challenging to evaluate, MCQA tasks are, in principle, easier to assess, as the model’s answer is thought to be simple to extract and is compared directly to a set of predefined choices. However, recent studies have started to question the reliability of MCQA evaluation, showing that multiple factors can significantly impact the reported performance of LLMs, especially when the model generates free-form text before selecting one of the answer choices. In this work, we shed light on the inconsistencies of MCQA evaluation strategies, which can lead to inaccurate and misleading model comparisons. We systematically analyze whether existing answer extraction methods are aligned with human judgment, and how they are influenced by answer constraints in the prompt across different domains. Our experiments demonstrate that traditional evaluation strategies often underestimate LLM capabilities, while LLM-based answer extractors are prone to systematic errors. Moreover, we reveal a fundamental trade-off between including format constraints in the prompt to simplify answer extraction and allowing models to generate free-form text to improve reasoning. Our findings call for standardized evaluation methodologies and highlight the need for more reliable and consistent MCQA evaluation practices.
See you in Vienna! 🇦🇹
Can we truly trust LLM evaluation scores?
Multiple-Choice Question Answering is one of the most widely used benchmarks for assessing LLMs across domains like math, science, commonsense reasoning and general knowledge. Since answer choices are predefined, evaluating models seems straightforward. However, our latest research reveals that current evaluation strategies introduce inconsistencies that may lead to incorrect conclusions about model performance.
In our paper, “Right Answer, Wrong Score: Uncovering the Inconsistencies of LLM Evaluation in Multiple-Choice Question Answering”, we conduct a systematic analysis of how different answer extraction methods influence reported accuracy. Our study highlights several critical challenges that affect the reliability of LLM evaluation.
Key Findings
- Traditional evaluation strategies underestimate LLM performance
- A trade-off exists between enforcing format constraints (for easy evaluation) and allowing free-form text (for better reasoning)
- LLM-based answer extractors are prone to systematic errors
We show that the way in which answers are extracted can significantly impact reported accuracy, raising concerns about the robustness of existing MCQA benchmarks. Our findings highlight the need for more reliable and standardized evaluation strategies to ensure fair model comparison.
Citations
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Plain text
Francesco Maria Molfese, Luca Moroni, Luca Gioffré, Alessandro Scirè, Simone Conia, and Roberto Navigli. 2025. Right Answer, Wrong Score: Uncovering the Inconsistencies of LLM Evaluation in Multiple-Choice Question Answering. In Findings of the Association for Computational Linguistics: ACL 2025, pages 18477–18494, Vienna, Austria. Association for Computational Linguistics.Markdown
[Right Answer, Wrong Score: Uncovering the Inconsistencies of LLM Evaluation in Multiple-Choice Question Answering](https://aclanthology.org/2025.findings-acl.950/) (Molfese et al., ACL 2025)BibTeX
@inproceedings{molfese-etal-2025-right, title = {Right Answer, Wrong Score: Uncovering the Inconsistencies of {LLM} Evaluation in Multiple-Choice Question Answering}, author = {Molfese, Francesco Maria and Moroni, Luca and Gioffr{\'e}, Luca and Scir{\`e}, Alessandro and Conia, Simone and Navigli, Roberto}, editor = {Che, Wanxiang and Nabende, Joyce and Shutova, Ekaterina and Pilehvar, Mohammad Taher}, booktitle = {Findings of the Association for Computational Linguistics: ACL 2025}, month = jul, year = {2025}, address = {Vienna, Austria}, publisher = {Association for Computational Linguistics}, url = {https://aclanthology.org/2025.findings-acl.950/}, doi = {10.18653/v1/2025.findings-acl.950}, pages = {18477--18494}, isbn = {979-8-89176-256-5}, }