Probing the Dynamics of Syntactic Ability Acquisition Throughout LLM Pretraining

Hiroshi Matsuda, Masayuki Asahara


Abstract
In this research, we introduce LoRA probing, a lightweight approach for observing how core syntactic abilities emerge during LLM pretraining. Leveraging OLMo-2’s public intermediate checkpoints, we trace learning curves across 24 pretraining stages on 33 Universal Dependencies languages by fine-tuning LoRA with step-by-step parsing instructions and a simple tabular output. To fit the relatively short context length of the OLMo-2, we design a compact 2-step-no-form prompt template and this matches the baseline in average accuracy while halving the context length and substantially increasing throughput, enabling efficient large-scale evaluation. Token Recall surpasses 0.9 within the first 1–2K pretraining steps, indicating that stable output formatting emerges early. Despite OLMo-2-7B’s English-centric pretraining, LAS exceeds 80 points in 29 of 33 languages; however, relations such as iobj and csubj show delayed onset and instability across many languages. LoRA probing thus provides a practical, reproducible lens on the cross-lingual dynamics of syntactic acquisition during LLM pretraining.
Anthology ID:
2026.udw-1.1
Volume:
Proceedings of the Ninth Workshop on Universal Dependencies (UDW 2026)
Month:
May
Year:
2026
Address:
Palma de Mallorca, Spain
Editors:
Çağrı Çöltekin, Kaja Dobrovoljc
Venues:
UDW | WS
SIG:
Publisher:
ELRA Language Resources Association (ELRA)
Note:
Pages:
1–48
Language:
External URL:
https://lrec.elra.info/lrec2026-ws-udw-01
DOI:
10.63317/2n8gkp49p3wg
Bibkey:
Cite (ACL):
Hiroshi Matsuda and Masayuki Asahara. 2026. Probing the Dynamics of Syntactic Ability Acquisition Throughout LLM Pretraining. In Proceedings of the Ninth Workshop on Universal Dependencies (UDW 2026), pages 1–48, Palma de Mallorca, Spain. ELRA Language Resources Association (ELRA).
Cite (Informal):
Probing the Dynamics of Syntactic Ability Acquisition Throughout LLM Pretraining (Matsuda & Asahara, UDW 2026)
Copy Citation: