Lexical Substitution is not Synonym Substitution: On the Importance of Producing Contextually Relevant Word Substitutes

Juraj Vladika, Stephen Meisenbacher, Florian Matthes

2025

Abstract

Lexical Substitution is the task of replacing a single word in a sentence with a similar one. This should ideally be one that is not necessarily only synonymous, but also fits well into the surrounding context of the target word, while preserving the sentence’s grammatical structure. Recent advances in Lexical Substitution have leveraged the masked token prediction task of Pre-trained Language Models to generate replacements for a given word in a sentence. With this technique, we introduce CONCAT, a simple augmented approach which utilizes the original sentence to bolster contextual information sent to the model. Compared to existing approaches, it proves to be very effective in guiding the model to make contextually relevant predictions for the target word. Our study includes a quantitative evaluation, measured via sentence similarity and task performance. In addition, we conduct a qualitative human analysis to validate that users prefer the substitutions proposed by our method, as opposed to previous methods. Finally, we test our approach on the prevailing benchmark for Lexical Substitution, CoInCo, revealing potential pitfalls of the benchmark. These insights serve as the foundation for a critical discussion on the way in which Lexical Substitution is evaluated.

Paper Citation

in Harvard Style

Vladika J., Meisenbacher S. and Matthes F. (2025). Lexical Substitution is not Synonym Substitution: On the Importance of Producing Contextually Relevant Word Substitutes. In Proceedings of the 17th International Conference on Agents and Artificial Intelligence - Volume 3: ICAART; ISBN 978-989-758-737-5, SciTePress, pages 1481-1488. DOI: 10.5220/0013389000003890

in Bibtex Style

@conference{icaart25,
author={Juraj Vladika and Stephen Meisenbacher and Florian Matthes},
title={Lexical Substitution is not Synonym Substitution: On the Importance of Producing Contextually Relevant Word Substitutes},
booktitle={Proceedings of the 17th International Conference on Agents and Artificial Intelligence - Volume 3: ICAART},
year={2025},
pages={1481-1488},
publisher={SciTePress},
organization={INSTICC},
doi={10.5220/0013389000003890},
isbn={978-989-758-737-5},
}

in EndNote Style

TY - CONF

JO - Proceedings of the 17th International Conference on Agents and Artificial Intelligence - Volume 3: ICAART
TI - Lexical Substitution is not Synonym Substitution: On the Importance of Producing Contextually Relevant Word Substitutes
SN - 978-989-758-737-5
AU - Vladika J.
AU - Meisenbacher S.
AU - Matthes F.
PY - 2025
SP - 1481
EP - 1488
DO - 10.5220/0013389000003890
PB - SciTePress