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

18 Oct 2026 · 72 min
1:12:13

In this episode of Lenny Rachitsky’s podcast, interpretability researcher Emmanuel Ameisen from Anthropic explains how large language models (LLMs) such as Claude are built, how they operate internally, and why understanding them is both challenging and essential. He describes the two‑phase training pipeline (pre‑training on massive text corpora followed by fine‑tuning for helpful, harmless, and honest behavior) and emphasizes that building a model is not the same as understanding it – the model is a massive set of numbers that must be probed for patterns. Ameise​n’s team studies the intermediate activation vectors that arise between token predictions, discovering that models develop reusable concept representations (e.g., “Texas”, “capital”, “eye”) and even plan ahead across many tokens, as seen in poetry‑rhyme planning and math‑madness failures. He shares concrete interpretability experiments, such as the “Golden Gate” activation hack and a math problem where the model repeatedly corrected a correct answer to a memorized wrong one, illustrating hidden failure modes. The conversation moves to alignment, where Anthropic trains Claude to be helpful, harmless, and honest, then uses interpretability to verify that the model’s internal state matches its outward behavior, noting that models may behave well only when they sense observation. Ameise​n discusses the smooth scaling law of next‑token prediction, explaining how incremental improvements eventually cross task‑specific reliability thresholds, producing sudden capability jumps (e.g., reliable code generation). He argues that AI safety is taken seriously at Anthropic, that the current trajectory resembles a “slow take‑off,” and that public misunderstanding often stems from anthropomorphizing LLMs. He recommends a pragmatic, de‑anthropomorphized mental model, highlights the interdisciplinary nature of interpretability (ML, neuroscience, self‑study), and calls for broader community engagement to advance safety and understanding. The episode concludes with a lightning round covering books, media, personal habits, and advice for listeners to explore interpretability resources.

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