Summary

A hands-on tutorial that trains a small one-layer transformer with a sparse autoencoder (SAE) to study which neurons activate for given inputs, making LLM internals observable. The goal is to find out whether LLM “thinking” patterns resemble human reasoning at the neuron level.

以實作方式訓練一個小型單層 Transformer 加稀疏自動編碼器(SAE),研究模型內部神經元對不同輸入的激活模式,探索 LLM 的「思考過程」是否類似人類推理。

Key Points

  • Trains a 1-layer transformer + SAE at small scale (millions of parameters)
  • Sparse autoencoders are used to decompose dense activations into interpretable sparse features
  • Neuron activation analysis reveals which features fire for a given prompt
  • Reader can skip training code and jump directly to the results section

Insights

Mechanistic interpretability via SAEs is becoming a standard probe for understanding model internals — Anthropic uses this approach at scale in published work. Building intuition by training a tiny model end-to-end is a good pedagogical approach, making abstract concepts concrete before tackling full-scale interpretability research.

Connections

Raw Excerpt

We will train a one-layer transformer + sparse autoencoder based small million parameter LLM, and then debug its thinking to see how similar the LLM’s thinking is to human thinking.