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On the Biology of a Large Language Model (Part 1)

Yannic Kilcher15 June 2026Watch on YouTube

What you'll learn

  • Claude 3.5 Haiku uses circuit tracing methodology to make the internal workings of the language model visible
  • Anthropic investigated how the lightweight production model deploys mechanisms and makes decisions in different contexts
  • Circuit analysis provides insight into which parts of the neural network are active in specific language processing tasks

Frequently asked questions

What is circuit tracing and how is it used to investigate language models?
Circuit tracing is a methodology Anthropic uses to map the internal mechanisms of large language models. This approach allows researchers to see which circuits and neurons are active when the model processes language.
Why do researchers investigate the internal structure of Claude 3.5 Haiku?
By understanding the internal mechanisms of language models, researchers can better predict how the model works, identify errors, and ultimately build safer systems.
How does circuit analysis differ from other methods for interpreting language models?
Circuit analysis focuses on mapping specific circuits and their interactions, providing more detailed insights than broader analysis methods.

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Description from the channel

An in-depth look at Anthropic's Transformer Circuit Blog Post https://transformer-circuits.pub/2025/attribution-graphs/biology.html Abstract: We investigate the internal mechanisms used by Claude 3.5 Haiku — Anthropic's lightweight production model — in a variety of contexts, using our circuit tracing methodology. Authors: Jack Lindsey†, Wes Gurnee*, Emmanuel Ameisen*, Brian Chen*, Adam Pearce*, Nicholas L. Turner*, Craig Citro*, David Abrahams, Shan Carter, Basil Hosmer, Jonathan Marcus, Michael Sklar, Adly Templeton, Trenton Bricken, Callum McDougall◊, Hoagy Cunningham, Thomas Henighan, Adam Jermyn, Andy Jones, Andrew Persic, Zhenyi Qi, T. Ben Thompson, Sam Zimmerman, Kelley Rivoire, Thomas Conerly, Chris Olah, Joshua Batson*‡ Links: Homepage: https://ykilcher.com Merch: https://ykilcher.com/merch YouTube: https://www.youtube.com/c/yannickilcher Twitter: https://twitter.com/ykilcher Discord: https://ykilcher.com/discord LinkedIn: https://www.linkedin.com/in/ykilcher If you want to support me, the best thing to do is to share out the content :) If you want to support me financially (completely optional and voluntary, but a lot of people have asked for this): SubscribeStar: https://www.subscribestar.com/yannickilcher Patreon: https://www.patreon.com/yannickilcher Bitcoin (BTC): bc1q49lsw3q325tr58ygf8sudx2dqfguclvngvy2cq Ethereum (ETH): 0x7ad3513E3B8f66799f507Aa7874b1B0eBC7F85e2 Litecoin (LTC): LQW2TRyKYetVC8WjFkhpPhtpbDM4Vw7r9m Monero (XMR): 4ACL8AGrEo5hAir8A9CeVrW8pEauWvnp1WnSDZxW7tziCDLhZAGsgzhRQABDnFy8yuM9fWJDviJPHKRjV4FWt19CJZN9D4n