Looped GPT-BERT: Trading Parameters for Computation in Small Language Modeling

Tingshuo Fan, Hongtao Mu, Tianyu Zhou, Hansen Liu, Tao Ji


Abstract
When training data are limited, increasing parameter count is not the only way to improve language-model performance. A small parameter set, when repeatedly applied, can also deliver comparable performance. We study Looped GPT-BERT in the BabyLM 2026 Strict-small setting, combining GPT-BERT’s masked next-token and causal language-modeling objectives with depth-wise parameter sharing. We train on a preprocessed 7.48M-word English corpus and compare objective ratios, non-looped and looped architectures, and loop counts. Our final 4×12 model uses four physical layers for twelve recurrent traversals and contains 12.18M parameters. The BabyLM 2026 leaderboard reports an Overall Average of 35.42 and an NLP Average of 48.48. Compared with public BabyLM 10M Strict-small GPT-2 and GPT-BERT baselines, it achieves comparable performance on selected linguistic and downstream metrics, including BLiMP and GLUE, with fewer parameters. The loop ablations show that additional recurrent computation can improve training and preserve strong performance on selected linguistic tasks, whereas poorer performance on other tasks may reveal an inherent limitation of the looped design: using only a few physical layers restricts the model’s representational space.
Anthology ID:
2026.babylm-main.70
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:
912–921
Language:
URL:
https://aclanthology.org/2026.babylm-main.70/
DOI:
Bibkey:
Cite (ACL):
Tingshuo Fan, Hongtao Mu, Tianyu Zhou, Hansen Liu, and Tao Ji. 2026. Looped GPT-BERT: Trading Parameters for Computation in Small Language Modeling. In Proceedings of the Second BabyLM Workshop, pages 912–921, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Looped GPT-BERT: Trading Parameters for Computation in Small Language Modeling (Fan et al., BabyLM 2026)
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PDF:
https://aclanthology.org/2026.babylm-main.70.pdf