Reasoning Models Better Express Their Confidence
Authors: name: Dongkeun Yoon; name: Seungone Kim; name: Sohee Yang; name: Sunkyoung Kim; name: Soyeon Kim; name: Yongil Kim; name: Eunbi Choi; name: Yireun Kim; name: Minjoon Seo
Published: 2025-05-20 15:19:00

Abstract: Despite their strengths, large language models (LLMs) often fail to
communicate their confidence accurately, making it difficult to assess when
they might be wrong and limiting their reliability. In this work, we
demonstrate that reasoning models-LLMs that engage in extended chain-of-thought
(CoT) reasoning-exhibit superior performance not only in problem-solving but
also in accurately expressing their confidence. Specifically, we benchmark six
reasoning models across six datasets and find that they achieve strictly better
confidence calibration than their non-reasoning counterparts in 33 out of the
36 settings. Our detailed analysis reveals that these gains in calibration stem
from the slow thinking behaviors of reasoning models-such as exploring
alternative approaches and backtracking-which enable them to adjust their
confidence dynamically throughout their CoT, making it progressively more
accurate. In particular, we find that reasoning models become increasingly
better calibrated as their CoT unfolds, a trend not observed in non-reasoning
models. Moreover, removing slow thinking behaviors from the CoT leads to a
significant drop in calibration. Lastly, we show that these gains are not
exclusive to reasoning models-non-reasoning models also benefit when guided to
perform slow thinking via in-context learning.