“Unfaithful chain-of-thought as nudged reasoning” by Paul Bogdan, Uzay Macar, Arthur Conmy, Neel Nanda

This piece is based on work conducted during MATS 8.0 and is part of a broader aim of interpreting chain-of-thought in reasoning models.

tl;dr

• Research on chain-of-thought (CoT) unfaithfulness shows how models’ CoTs may omit information that is relevant to their final decision.
• Here, we sketch hypotheses for why key information may be omitted from CoTs:
  • Training regimes could teach LLMs to omit information from their reasoning.
  • But perhaps more importantly, statements within a CoT generally have functional purposes, and faithfully mentioning some information may carry no benefits, so models don’t do it.
• We make further claims about what's going on in faithfulness experiments and how hidden information impacts a CoT:
  • Unfaithful CoTs are often not purely post hoc rationalizations and instead can be understood as biased reasoning.
  • Models continually make choices during CoT, repeatedly drawing new propositions supporting or discouraging different answers.
  • Hidden information can nudge [...]

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Outline:

(00:21) tl;dr

(01:54) Unfaithfulness

(04:16) CoT is functional, and faithfulness lacks benefits

(09:29) Hidden information can nudge CoTs

(09:48) Silent, soft, and steady spectres

(13:48) Nudges are plausible

(14:42) Nudged CoTs are hard to spot

(15:49) Safety and CoT monitoring

(18:11) Final summary

The original text contained 5 footnotes which were omitted from this narration.

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First published:
July 22nd, 2025

Source:
https://www.lesswrong.com/posts/vPAFPpRDEg3vjhNFi/unfaithful-chain-of-thought-as-nudged-reasoning

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Narrated by TYPE III AUDIO.

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