Morables: A benchmark for assessing abstract moral reasoning in LLMs with fables

Marcuzzo, Matteo, Zangari, Alessandro, Albarelli, Andrea, Camacho-Collados, Jose ORCID: https://orcid.org/0000-0003-1618-7239 and Pilehvar, Mohammad Taher 2025. Morables: A benchmark for assessing abstract moral reasoning in LLMs with fables. Presented at: 2025 Conference on Empirical Methods in Natural Language Processing, Suzhou, China, 4-9 November 2025. Published in: Christodoulopoulos, Christos, Chakraborty, Tanmoy, Rose, Carolyn and Peng, Violet eds. Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing. Association for Computational Linguistics, pp. 27715-27739. 10.18653/v1/2025.emnlp-main.1411

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Abstract

As LLMs excel on standard reading comprehension benchmarks, attention is shifting toward evaluating their capacity for complex abstract reasoning and inference. Literature-based benchmarks, with their rich narrative and moral depth, provide a compelling framework for evaluating such deeper comprehension skills. Here, we present Morables, a human-verified benchmark built from fables and short stories drawn from historical literature. The main task is structured as multiple-choice questions targeting moral inference, with carefully crafted distractors that challenge models to go beyond shallow, extractive question answering. To further stress-test model robustness, we introduce adversarial variants designed to surface LLM vulnerabilities and shortcuts due to issues such as data contamination. Our findings show that, while larger models outperform smaller ones, they remain susceptible to adversarial manipulation and often rely on superficial patterns rather than true moral reasoning. This brittleness results in significant self-contradiction, with the best models refuting their own answers in roughly 20% of cases depending on the framing of the moral choice. Interestingly, reasoning-enhanced models fail to bridge this gap, suggesting that scale - not reasoning ability - is the primary driver of performance.

Item Type:	Conference or Workshop Item - published (Paper)
Date Type:	Publication
Status:	Published
Schools:	Schools > Computer Science & Informatics
Publisher:	Association for Computational Linguistics
ISBN:	979-8-89176-332-6
Date of First Compliant Deposit:	16 June 2026
Last Modified:	02 Aug 2026 01:19
URI:	https://orca.cardiff.ac.uk/id/eprint/187578

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