Causal Interventions Reveal Shared Structure Across English Filler–Gap Constructions

Sasha Boguraev, Christopher Potts, Kyle Mahowald


Abstract
Language Models (LMs) have emerged as powerful sources of evidence for linguists seeking to develop theories of syntax. In this paper, we argue that causal interpretability methods, applied to LMs, can greatly enhance the value of such evidence by helping us characterize the abstract mechanisms that LMs learn to use. Our empirical focus is a set of English filler–gap dependency constructions (e.g., questions, relative clauses). Linguistic theories largely agree that these constructions share many properties. Using experiments based in Distributed Interchange Interventions, we show that LMs converge on similar abstract analyses of these constructions. These analyses also reveal previously overlooked factors – relating to frequency, filler type, and surrounding context – that could motivate changes to standard linguistic theory. Overall, these results suggest that mechanistic, internal analyses of LMs can push linguistic theory forward.
Anthology ID:
2025.emnlp-main.1271
Volume:
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Month:
November
Year:
2025
Address:
Suzhou, China
Editors:
Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
Venue:
EMNLP
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Publisher:
Association for Computational Linguistics
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Pages:
25032–25053
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URL:
https://preview.aclanthology.org/ingest-emnlp/2025.emnlp-main.1271/
DOI:
Bibkey:
Cite (ACL):
Sasha Boguraev, Christopher Potts, and Kyle Mahowald. 2025. Causal Interventions Reveal Shared Structure Across English Filler–Gap Constructions. In Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing, pages 25032–25053, Suzhou, China. Association for Computational Linguistics.
Cite (Informal):
Causal Interventions Reveal Shared Structure Across English Filler–Gap Constructions (Boguraev et al., EMNLP 2025)
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