Cross-Linguistic Effects in Bilingual Phoneme BabyLMs

Nikitas Theodoropoulos, Maria Lymperaiou, Giorgos Filandrianos


Abstract
Cross-linguistic effects are a central topic in bilingual first-language acquisition. Artificial learners can help investigate L1-L2 interactions by enabling controlled comparisons across language combinations and learning conditions. Recent work explores this direction by training bilingual language models under developmentally plausible constraints. However, human and model learners still diverge in fundamental ways, with one major difference being input modality: children learn primarily from spoken input, whereas language models are typically trained on orthographic text. To reduce this gap, researchers have trained models on phonemic representations of speech. In this work, we combine these research directions to train bilingual BabyLMs with phonemic input. We keep English fixed as the L2 and vary the L1 across German, Swedish, Persian, and Basque, selected to represent contrasting combinations of syntactic and phoneme-inventory distance from English. Our results show stronger L1-related variation in grammatical learning trajectories under phonemic than orthographic input, while early lexical differences align with phoneme-inventory similarity.
Anthology ID:
2026.babylm-main.26
Volume:
Proceedings of the Second BabyLM Workshop
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Leshem Choshen, Ryan Cotterell, Mustafa Omer Gul, Jaap Jumelet, Tal Linzen, Aaron Mueller, Suchir Salhan, Raj Sanjay Shah, Alex Warstadt, Ethan Gotlieb Wilcox
Venues:
BabyLM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
320–332
Language:
URL:
https://aclanthology.org/2026.babylm-main.26/
DOI:
Bibkey:
Cite (ACL):
Nikitas Theodoropoulos, Maria Lymperaiou, and Giorgos Filandrianos. 2026. Cross-Linguistic Effects in Bilingual Phoneme BabyLMs. In Proceedings of the Second BabyLM Workshop, pages 320–332, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Cross-Linguistic Effects in Bilingual Phoneme BabyLMs (Theodoropoulos et al., BabyLM 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.babylm-main.26.pdf