Perturbation: A simple and efficient adversarial tracer for representation learning in language models

Joshua Rozner, Cory Shain


Abstract
Linguistic representation learning in deep neural language models (LMs) has been studied for decades, but finding representations in LMs remains an unsolved problem. On the one hand, unconstrained alignments may trivialize the notion of representation (Sutter et al., 2025); on the other, even recently popularized linear approaches may not always be faithful to natural model behavior (Arora et al., 2024). Here we escape this dilemma by reconceptualizing representations not as patterns of activation but as conduits for learning. Our approach is simple: we perturb an LM by fine-tuning it on a single adversarial example and measure how this perturbation “infects” other examples. Perturbation makes no geometric assumptions, and unlike other methods, it does not find representations where it should not (e.g., in untrained LMs). But in trained LMs, perturbation reveals structured transfer at multiple linguistic grain sizes, suggesting that LMs both generalize along representational lines and acquire linguistic abstractions from experience alone.
Anthology ID:
2026.emnlp-main.1677
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
Note:
Pages:
38151–38182
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1677/
DOI:
Bibkey:
Cite (ACL):
Joshua Rozner and Cory Shain. 2026. Perturbation: A simple and efficient adversarial tracer for representation learning in language models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 38151–38182, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Perturbation: A simple and efficient adversarial tracer for representation learning in language models (Rozner & Shain, EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.1677.pdf