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

Vedant Palit, Florent Draye, Terry Jingchen Zhang, Bernhard Schölkopf, Zhijing Jin


Abstract
Transcoder attribution graphs are usually trained to explain why a model assigns high probability to a particular next token. We introduce Concept-Targeted Attribution (CTA), which instead trains attribution graphs with respect to a linear probe direction. CTA therefore yields probe-specific circuits that explain why an internal concept representation arises in a prompt, independently of whether it is expressed in the generated token. Using Cross-Layer Transcoders, we show that these probe-targeted graphs contain predictive structure: graph-level features predict probe accuracy across four widely studied concept categories (𝜌 = 0.91, R2 = 0.84), while local features identify the sparse components driving per-prompt classification. This connects probe performance to interpretable circuit structure, allowing us to ask not only whether a probe works, but which internal computations make it work. Causal ablations further show that probe-targeted and logit-targeted graphs capture functionally distinct mechanisms. Removing probe-relevant features reduces internal concept scores while largely preserving generated tokens, whereas removing logit-relevant features changes the generated token in 92% to 100% of cases with near-zero effect on probe scores. CTA provides a framework for moving from behavioral probe accuracy to mechanistic explanations of probe performance, enabling more detailed audits of internal concept representations, including safety-critical ones.
Anthology ID:
2026.emnlp-main.1728
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
39424–39454
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URL:
https://aclanthology.org/2026.emnlp-main.1728/
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Cite (ACL):
Vedant Palit, Florent Draye, Terry Jingchen Zhang, Bernhard Schölkopf, and Zhijing Jin. 2026. How Do Linear Probes Emerge? A Circuit-Tracing Framework with Concept-Targeted Attribution. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 39424–39454, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
How Do Linear Probes Emerge? A Circuit-Tracing Framework with Concept-Targeted Attribution (Palit et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1728.pdf