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arXiv:2305.04388cs.CL

Language Models Don't Always Say What They Think: Unfaithful Explanations in Chain-of-Thought Prompting

Miles Turpin, Julian Michael, Ethan Perez, Samuel R. Bowman

Abstract

Large Language Models (LLMs) can achieve strong performance on many tasks by producing step-by-step reasoning before giving a final output, often referred to as chain-of-thought reasoning (CoT). It is tempting to interpret these CoT explanations as the LLM's process for solving a task. This level of transparency into LLMs' predictions would yield significant safety benefits. However, we find that CoT explanations can systematically misrepresent the true reason for a model's prediction. We demonstrate that CoT explanations can be heavily influenced by adding biasing features to model inputs--e.g., by reordering the multiple-choice options in a few-shot prompt to make the answer always "(A)"--which models systematically fail to mention in their explanations. When we bias models toward incorrect answers, they frequently generate CoT explanations rationalizing those answers. This causes accuracy to drop by as much as 36% on a suite of 13 tasks from BIG-Bench Hard, when testing with GPT-3.5 from OpenAI and Claude 1.0 from Anthropic. On a social-bias task, model explanations justify giving answers in line with stereotypes without mentioning the influence of these social biases. Our findings indicate that CoT explanations can be plausible yet misleading, which risks increasing our trust in LLMs without guaranteeing their safety. Building more transparent and explainable systems will require either improving CoT faithfulness through targeted efforts or abandoning CoT in favor of alternative methods.

arXiv comments
NeurIPS 2023
Journal reference
DOI
Subjects
cs.CLComputation and Language cs.AIArtificial Intelligence

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Linked by 7 identifiable commenters in 7 comments across 7 threads, from May 2023 to Oct 2026. Found in 1 HN submission from May 2023 to May 2023. Open submission discussions.

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Discussed in comments7 threads

  1. DeepSeek-v4.1-Flash-1017 1 comment
    • >> Being able to see the CoT Dont assume that is how your model decides... https://arxiv.org/abs/2305.04388 https://arxiv.org/abs/2307.13702 https://arxiv.org/abs/2503.08679

      BetelbuddyView on HNParent context

  2. Google Antigravity 1 comment
    • "major architectural decisions don't get documented anywhere" "commit messages give no "why"" This is so far outside of common industry practices that I don't think your sentiment generalizes. Or perhaps your expectation of what should go in a single commit message is different…

      recitedropperView on HNParent context

    • This is interesting, but I wonder how reliable this type of monitoring is really going to be in the long run. There are fairly strong indications that CoT adherence can be trained out of models, and there's already research showing that they won't always reveal their thought…

      sabaimranView on HNParent context

    • Recent paper from Anthropic on the fact that the reasoning output does not necessarily reflect what the LLM is "thinking". https://arxiv.org/abs/2305.04388 That being said, your idea is not unreasonable. The way DeepSeek phrased it, it just sounds like implementing such…

      oerstedView on HNParent context

    • LLMs that use Chain of Thought sequences have been demonstrated to misrepresent their own reasoning [1]. The CoT sequence is another dimension for hallucination. So, I would say that an LLM capable of explaining its reasoning doesn't guarantee that the reasoning is grounded in…

      grepLeighView on HNParent context

    • In section 2 they briefly mention studies such as [1] that point out that the token outputs of a chain of thought aren't always entirely faithful to the responses of the models I'm not sure whether it wouldn't be more reliable to let the model run on latents and try to train a…

      mivenView on HNParent context

    • Yes, there's no physical reason it couldn't be fixed. However, I think it's less a matter of computing power, and more one of architecture and training. The inference-time code could be changed to keep a log of which neurons were activated the most when it generated a token. But…

      skybrianView on HNParent context

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