arXiv Machine Learning

How Do Linear Probes Emerge? A Circuit-Tracing Framework with Concept-Targeted Attribution

The paper introduces Concept-Targeted Attribution (CTA), a method that trains attribution graphs to explain the emergence of internal concept representations in language models, rather than just the final token prediction. CTA produces probe-specific circuits that reveal which internal computations drive a linear probe’s accuracy, and cross-layer transcoders demonstrate that these graphs contain predictive structure across multiple concept categories. Causal ablations show that probe-targeted and logit-targeted graphs capture distinct mechanisms, with probe-relevant features affecting internal concept scores and logit-relevant features altering generated tokens.

arXiv Machine Learning
Sep 23

Matryoshka attribution: Learning to attribute language model outputs to representations and weights

Matryoshka Attribution (MAttr) is a mask‑learning method that identifies nested subsets of a language model’s internal components by minimizing downstream loss. It uses a differentiable sigmoid top‑k operator and randomizes sparsity during training to produce an attribution ordering of components. MAttr tops the Mechanistic Interpretability Benchmark leaderboard and can be applied via reinforcement learning to pinpoint weight changes that control behaviors such as refusal in Llama 3.1 8B Instruct, where restoring just 1% of weights removes refusals while preserving capabilities.

By Aryaman Arora, Kirill Acharya, Nathan Hu, Yanzhe Zhang, Noah Goodman, Dan Jurafsky, Christopher Potts
arXiv Machine Learning
Oct 23

Rethinking SAE Evaluation: An Atomic Interpretable Unit Framework Reveals Hidden Polysemanticity and Redundancy

The paper introduces a new framework for evaluating sparse autoencoders (SAEs) by requiring their features to form an atomic interpretable unit basis, a coordinate system for semantically meaningful explanation. It formalizes this objective and organizes existing and new metrics, such as DAME, into a comprehensive benchmarking framework. Experiments across many SAE architectures reveal that some models appear monosemantic under current metrics yet are functionally polysemantic, with dominant features being less interpretable and more redundant.

By Riteng Zhang, Xiaoqian Wang
arXiv AI
Sep 25

Every Component Is a Lookup: One Linear Graph for Interaction, Composition and Attribution

The paper proposes that two architectural assumptions—(1) attention and MLPs share a key‑value form <phi(S)>U, and (2) components read from an additive residual stream—are sufficient to answer three interpretability questions: component interaction, information routing, and token attribution. By treating these selections as a computational graph, the authors develop Unpack, a backward attribution method that validates interaction scores, recovered routes, and token attribution against established tests across models ranging from 160M to 6.9B parameters. The study also shows that contribution and causal effect can differ, with a recognizable signature in how components change when a task is removed.

By Po-Kai Chen, Aske Plaat, Niki van Stein