Surprisal Dynamics for the Detection of Multi-Word Expressions in English

Diego Alves, Sergei Bagdasarov, Elke Teich


Abstract
This work examines the potential of surprisal slope as a feature for identifying multi-word expressions (MWEs) in English, leveraging token-level surprisal estimates from the GPT-2 language model. Evaluations on the DiMSUM and SemEval-2022 datasets reveal that surprisal slope provides moderate yet meaningful discriminative power with a trade-off between specificity and coverage: while high recall indicates that surprisal slope captures many true MWEs, the slightly lower precision reflects false positives, particularly for non-MWEs that follow formulaic patterns (e.g., adjective-noun or verb-pronoun structures). The method performs particularly well for conventionalized expressions, such as idiomatic bigrams in the SemEval-2022 corpus. Both idiomatic and literal usages of these bigrams exhibit negative slopes, with idiomatic instances generally showing a more pronounced decrease.Overall, surprisal slope offers a cognitively motivated and interpretable signal that complements existing MWE identification methods, particularly for conventionalized expressions.
Anthology ID:
2025.findings-ijcnlp.72
Volume:
Proceedings of the 14th International Joint Conference on Natural Language Processing and the 4th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics
Month:
December
Year:
2025
Address:
Mumbai, India
Editors:
Kentaro Inui, Sakriani Sakti, Haofen Wang, Derek F. Wong, Pushpak Bhattacharyya, Biplab Banerjee, Asif Ekbal, Tanmoy Chakraborty, Dhirendra Pratap Singh
Venue:
Findings
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Publisher:
The Asian Federation of Natural Language Processing and The Association for Computational Linguistics
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Pages:
1185–1194
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URL:
https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.findings-ijcnlp.72/
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Cite (ACL):
Diego Alves, Sergei Bagdasarov, and Elke Teich. 2025. Surprisal Dynamics for the Detection of Multi-Word Expressions in English. In Proceedings of the 14th International Joint Conference on Natural Language Processing and the 4th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics, pages 1185–1194, Mumbai, India. The Asian Federation of Natural Language Processing and The Association for Computational Linguistics.
Cite (Informal):
Surprisal Dynamics for the Detection of Multi-Word Expressions in English (Alves et al., Findings 2025)
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https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.findings-ijcnlp.72.pdf