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Marylou Fauchard

marylou.fauchard@mila.quebec
Maîtrise recherche - UdeM
Superviseur⋅e principal⋅e
Margarida Carvalho
Co-supervisor
Golnoosh Farnadi
Sujets de recherche
Alignement de l'IA
Apprentissage par renforcement
Grands modèles de langage (LLM)
Recherche opérationnelle

Publications

Reasoning with Preference Constraints: A Benchmark for Language Models in Many-to-One Matching Markets
Marylou Fauchard
Florian Carichon
Margarida Carvalho
Golnoosh Farnadi
2026-08-01
Transactions on Machine Learning Research (accepté)
doi.org
openreview.net
Even More Deception: Objective Misalignment in Mixed-Motive LLM Multi-Agent Systems
Marylou Fauchard
Florian Carichon
Margarida Carvalho
Golnoosh Farnadi
Large Language Models (LLMs)-powered multi-agent systems are increasingly deployed in mixed-motive environments, where agents operate under … (voir plus)asymmetric information and strategic deception due to conflicting or hidden objectives. In these settings, misalignment with collective goals becomes a central concern. We propose a novel framework for evaluating objective misalignment using the social deduction game Werewolf, modifying the objective of a single agent while preserving its assigned role. Across LLMs from four different model families and sizes, four player roles, and three objective formulations, we introduce a dual analysis of the agents' internal reasoning and their public cheap-talk behavior (i.e costless, non-binding communication that does not directly affect the agents' utilities), complemented by an analysis of game outcomes. Our results show that objective misalignment undermines outcomes in inherently adversarial environments, an effect exacerbated by asymmetric information and specialized roles. While compromised agents consistently develop distinct objective-dependent reasoning strategies, these adaptations remain largely invisible in their public behavior. More broadly, our findings suggest that even subtle objective misalignment can profoundly affect collective decision-making, highlighting the need for effective mitigation strategies for LLM-based multi-agent systems.
2026-07-27
arXiv (prépublication)
doi.org
arxiv.org
Objective Misalignment in LLM-based Multi Agent Social Deception Game
Marylou Fauchard
Florian Carichon
Margarida Carvalho
Golnoosh Farnadi
Large language model–based multi-agent systems have attracted increasing attention for their strong performance in collaborative tasks and… (voir plus) social simulations. However, these interactive settings also introduce vulnerabilities, as a single agent's hidden goals and misaligned behavior can propagate misleading or malicious information throughout the system. In this work, we study these risks in the context of social deception games. We focus on the Werewolf Game, which requires agents to reason, communicate, and collaborate under asymmetric and incomplete information. We modify the individual objectives of some agents to induce benevolent, individualistic, and malevolent strategies that can make agents depart from the objectives of their own team. We evaluate how objective divergence affects game outcomes, collaboration, and goal satisfaction. Misaligned agents often succeed in achieving their own objectives, with effects amplified by role-based power asymmetries. Qualitative analyses further show that agents remain coherent and adaptive, strategically adjusting their reasoning, communication, voting behavior, and influence on group dynamics. These results indicate that risks in LLM-based multi-agent systems extend beyond collaborative task settings and persist even in environments where competition is structurally expected.
2026-02-28
AIWILD @ International Conference on Learning Representations (publié)
openreview.net
openreview.net
Multilingual Amnesia: On the Transferability of Unlearning in Multilingual LLMs
Alireza Dehghanpour Farashah
Aditi Khandelwal
Marylou Fauchard
Zhuan Shi
Negar Rostamzadeh
Golnoosh Farnadi
As multilingual large language models become more widely used, ensuring their safety and fairness across diverse linguistic contexts present… (voir plus)s unique challenges. While existing research on machine unlearning has primarily focused on monolingual settings, typically English, multilingual environments introduce additional complexities due to cross-lingual knowledge transfer and biases embedded in both pretraining and fine-tuning data. In this work, we study multilingual unlearning using the Aya-Expanse 8B model under two settings: (1) data unlearning and (2) concept unlearning. We extend benchmarks for factual knowledge and stereotypes to ten languages through translation: English, French, Arabic, Japanese, Russian, Farsi, Korean, Hindi, Hebrew, and Indonesian. These languages span five language families and a wide range of resource levels. Our experiments show that unlearning in high-resource languages is generally more stable, with asymmetric transfer effects observed between typologically related languages. Furthermore, our analysis of linguistic distances indicates that syntactic similarity is the strongest predictor of cross-lingual unlearning behavior.
2025-12-31
Conference of the European Chapter of the Association for Computational Linguistics (publié)
doi.org
arxiv.org