Belief or Circuitry? Causal Evidence for In-Context Graph Learning

Katharine Kowalyshyn, Timothy Duggan, Daniel Little, Michael C Hughes


Abstract
How do LLMs learn in-context? Is it by pattern-matching recent tokens, or by inferring latent structure? We probe this question using a toy graph random-walk across two competing graph structures. We present behavioral, representational, and causal evidence that neither account alone is sufficient. First, a complexity-weighted sigmoid model captures topology-dependent evidence accumulation, and PCA shows that both graph topologies are visually recoverable at intermediate mixture ratios. Second, residual-stream activation patching and graph-difference steering causally intervene on this graph-family signal: late-layer patching almost fully transfers the clean graph preference, while linear steering moves predictions in the intended direction and fails under norm-matched and label-shuffled controls. An explicit transition-cache baseline reproduces the fitted asymmetry and held-out-edge transfer, however, so these results do not by themselves distinguish global inference from local copying. Taken together, our findings are consistent with a dual-mechanism account in which structure inference and induction circuits operate in parallel, but do not uniquely identify it.
Anthology ID:
2026.blackboxnlp-1.29
Volume:
Proceedings of the 9th BlackboxNLP Workshop: Analyzing and Interpreting Neural Networks for NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Dana Arad, Yonatan Belinkov, Hanjie Chen, Nils Feldhus, Aaron Mueller, Hosein Mohebbi, Gabriele Sarti, Martin Tutek
Venues:
BlackboxNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
477–486
Language:
URL:
https://aclanthology.org/2026.blackboxnlp-1.29/
DOI:
Bibkey:
Cite (ACL):
Katharine Kowalyshyn, Timothy Duggan, Daniel Little, and Michael C Hughes. 2026. Belief or Circuitry? Causal Evidence for In-Context Graph Learning. In Proceedings of the 9th BlackboxNLP Workshop: Analyzing and Interpreting Neural Networks for NLP, pages 477–486, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Belief or Circuitry? Causal Evidence for In-Context Graph Learning (Kowalyshyn et al., BlackboxNLP 2026)
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PDF:
https://aclanthology.org/2026.blackboxnlp-1.29.pdf