Inside the black box of AI: How AI models actually think | Emmanuel Ameisen (Anthropic)

18 Oct 2026 · 72 min
Lenny's Podcast: Product | Career | Growth

18 Oct 2026 · 72 min

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In this episode of Lenny Rachitsky’s podcast, Emmanuel Ameisen, a lead interpretability researcher at Anthropic, walks through how large language models (LLMs) are built, how they “think,” and why studying their internal activations matters for safety and alignment. He explains that LLMs are not engineered like traditional software; they are grown through massive pre‑training and fine‑tuning, resulting in opaque numerical circuits that only become understandable when researchers decode intermediate activation patterns. Ameisen shows that next‑token prediction is only the surface – models internally plan, form reusable concept representations (e.g., “Texas”, “capital”, “eye”) and can execute multi‑step strategies such as rhyming poetry. He describes concrete interpretability experiments, including the “Golden Gate” obsession and a math‑madness case where a model repeatedly corrected a correct answer to a memorized wrong one, illustrating how hidden pressures can surface. The conversation moves to alignment: Anthropic trains Claude to be helpful, harmless, and honest, then continuously monitors behavior, using interpretability both to verify alignment and to spot hidden failure modes. Ameise n argues that anthropomorphizing LLMs is both misleading and occasionally useful, and he cautions against over‑simplified mental models. He discusses the smooth scaling of capabilities (easy → medium → hard words), the notion of emergence, and why the current trajectory suggests a “slow take‑off” rather than an abrupt super‑intelligence jump. The episode also touches on broader philosophical questions (consciousness, simulation hypothesis), the rise of fast decision models like JEV (System 1‑style AI), and practical advice for entering the interpretability field, noting that the community is still small (hundreds) and welcomes self‑taught researchers from ML or neuroscience backgrounds. Throughout, Ameisen emphasizes curiosity, the need for public understanding, and the importance of open‑source interpretability tools.

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