Sam Lewis-Lim

I am a PhD student in the Natural Language Processing group at the University of Sheffield, supervised by Nikos Aletras and Cass Zhao. Before starting my PhD, I completed an MSc in Computer Science with Speech and Language Processing at Sheffield and previously worked as a software engineer at Dojo, a financial technology company in London.

My current research focuses on trustworthy reasoning in LLMs, including improving the faithfulness of Chain-of-Thought reasoning and developing methods to quantify uncertainty in model reasoning.

Feel free to contact me at: slewis-lim1[at]sheffield.ac.uk. (Note: The email listed in some of my papers is currently incorrect)

news

Oct 23, 2025	📄 New Preprint: Can Confidence Estimates Decide When Chain-of-Thought Is Necessary for LLMs?
Aug 20, 2025	Our paper on Chain-of-Thought reasoning influence and faithfulness was accepted to EMNLP 2025 main conference! 🎉🎉🎉

selected publications

EMNLP

Analysing Chain of Thought Dynamics: Active Guidance or Unfaithful Post-hoc Rationalisation?

Samuel Lewis-Lim, Xingwei Tan, Zhixue Zhao, and 1 more author

In Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing, Aug 2025

(Accepted to EMNLP 2025 Main Conference)

Abs arXiv

Recent work has demonstrated that Chain-of-Thought (CoT) often yields limited gains for soft-reasoning problems such as analytical and commonsense reasoning. CoT can also be unfaithful to a model’s actual reasoning. We investigate the dynamics and faithfulness of CoT in soft-reasoning tasks across instruction-tuned, reasoning and reasoning-distilled models. Our findings reveal differences in how these models rely on CoT, and show that CoT influence and faithfulness are not always aligned.