ICA Lens finds interpretable LLM directions via non-Gaussianity, no SAE training needed

sarahwiegreffe · x · 2026-10-22

UMD researchers show that non-Gaussianity is a statistical signature of interpretable directions: projections of residual-stream activations along SAE decoder directions are far more non-Gaussian than random ones, with recurring patterns occupying one tail. They introduce ICA Lens, a workflow to discover, annotate, and evaluate non-Gaussian directions directly in activation space without training a sparse dictionary. Across GPT-2 Small, Gemma 2 2B, and Qwen 3.5 9B Base, recovered directions capture coherent lexical, syntactic, and semantic patterns under both human and LLM evaluation. Installable via pip install icalens, with paper, website, and GitHub available.

Related event: Reviving ICA: Fixing Evaluation Bug Makes Classic Method Competitive with SAEs for LLM Interpretability(7 posts)→

Original post →

More from Research

Research channel →