Source
When this applies
when building understanding of any opaque complex system from scratch, through successive representational breakthroughs
The takeaway
Understanding an opaque complex system progresses by first diagnosing the structural reason for illegibility, then building tools that relieve that structural constraint, then assembling the resulting legible units into causal chains.
Why it works
Each stage solved the bottleneck of the previous: first diagnosing that models cram many concepts into few neurons (superposition), then giving the system enough 'representational space' to separate concepts cleanly (sparse autoencoders producing up to 30M features), then connecting those separated features across layers into causal chains (circuits) that explain multi-step reasoning.
One level up
Treat interpretability/understanding-building as an iterative engineering problem with its own research roadmap, not a one-shot insight.
Where it stops holding
This stops working when the underlying system's units of computation don't decompose into sparse, separable features even with more representational space — i.e., if superposition isn't the right diagnosis for all model behavior.
Detail
procedure:- Diagnose: toy models of superposition reveal models cram multiple meanings per neuron
- Relieve: sparse autoencoders give models more representational space, producing millions of nameable features (e.g. 30M in Claude 3 Sonnet)
- Assemble: circuits work links features across layers into causal chains explaining multi-step reasoning (medical diagnosis, addition, fact retrieval)
benchmarks: {"toy_model_features":"16,000","claude3_sonnet_features":"30,000,000"}
rationale: Each breakthrough happened roughly every six months and built directly on removing the bottleneck exposed by the prior one.
In their words
Fast forward nine months, we go from a two layer transformer to our Claude three SONNET Frontier model at the time and fit up to 30,000,000 features.