On the Interplay between Positional Encodings, Morphological Complexity, and Word Order Flexibility

Kushal Tatariya, Wessel Poelman, Miryam de Lhoneux


Abstract
Language model architectures are predominately first created for English and afterwards applied to other languages. This can lead to problems for languages that are structurally different from English. We study one specific architectural choice: positional encodings. We do this through the lens of the trade-off hypothesis: the supposed interplay between morphological complexity and word order flexibility. This hypothesis states there exists a trade-off between the two: a more morphologically complex language can have a more flexible word order, and vice-versa. Positional encodings are a direct target to investigate the implications of this hypothesis in relation to language modelling. We pre-train and evaluate three monolingual model variants with absolute, relative and no position encodings for seven typologically diverse languages and evaluate on four downstream tasks. We fail to find a consistent trend with various proxies for morphological complexity and word order flexibility. Our work shows choice of tasks, languages, and metrics are essential for drawing stable conclusions.
Anthology ID:
2025.ijcnlp-long.95
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
Venues:
IJCNLP | AACL
SIG:
Publisher:
The Asian Federation of Natural Language Processing and The Association for Computational Linguistics
Note:
Pages:
1761–1778
Language:
URL:
https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.ijcnlp-long.95/
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Bibkey:
Cite (ACL):
Kushal Tatariya, Wessel Poelman, and Miryam de Lhoneux. 2025. On the Interplay between Positional Encodings, Morphological Complexity, and Word Order Flexibility. 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 1761–1778, Mumbai, India. The Asian Federation of Natural Language Processing and The Association for Computational Linguistics.
Cite (Informal):
On the Interplay between Positional Encodings, Morphological Complexity, and Word Order Flexibility (Tatariya et al., IJCNLP-AACL 2025)
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https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.ijcnlp-long.95.pdf