Loop Before You Leap: What Recurrent Depth Can and Cannot Buy in Data-Limited Pretraining

Daichi Hotta, Yohei Kobashi, Takeshi Kojima, Yusuke Iwasawa, Yutaka Matsuo


Abstract
Multimodal models have often scored below text-only baselines in the BabyLM Challenge (Klerings et al., 2024; Takmaz et al., 2025). We test whether additional recurrent computation helps close this gap. Recurrence increases computation by reusing layers without adding parameters or training data. Using a single implementation, we compare standard and looped Transformers under a 100M-word budget, with three seeds per main condition. Each image is represented by one feature vector from a frozen DINOv2 encoder, used as a prefix token. Caption words count toward the budget, so multimodal training also changes the language data. In a pre-registered text-only comparison, a 12-layer stack repeated four times exceeds a standard 48-layer Transformer by 5.4 BLiMP percentage points at matched inference compute. However, multimodal training lowers BLiMP accuracy by about 3.8 points in both architectures, with no clear mitigation from recurrence. An exploratory loop-side no-image control, trained with the multimodal language data and batching schedule, scores 5.7 points below the text-only baseline. Adding the visual prefix raises accuracy by 1.85 points on average, but this contrast is uncertain with three seeds. These results suggest that changes in language data and its presentation are a major source of the drop. Diagnostic tests show that the models use visual information; its contribution to grammatical generalization remains uncertain under this single-vector interface.
Anthology ID:
2026.babylm-main.43
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:
543–562
Language:
URL:
https://aclanthology.org/2026.babylm-main.43/
DOI:
Bibkey:
Cite (ACL):
Daichi Hotta, Yohei Kobashi, Takeshi Kojima, Yusuke Iwasawa, and Yutaka Matsuo. 2026. Loop Before You Leap: What Recurrent Depth Can and Cannot Buy in Data-Limited Pretraining. In Proceedings of the Second BabyLM Workshop, pages 543–562, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Loop Before You Leap: What Recurrent Depth Can and Cannot Buy in Data-Limited Pretraining (Hotta et al., BabyLM 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.babylm-main.43.pdf