A Pre-Training Analogue of Grokking in Language Models: Tracing Delayed Grammatical Generalization

Sherin Muckatira, Namrata Shivagunde, Vijeta Deshpande, Anna Rumshisky


Abstract
Grokking, the phenomenon in which neural networks generalize long after fitting their training data, has been studied in supervised settings on many epochs. LLM pre-training instead involves next-token prediction over an unlabeled corpus, with limited data repetition and no explicit train/validation split. To address this, we propose an exposure-based framework that enables the study of grokking-like dynamics during LLM pre-training. We ground our evaluation in BLiMP minimal pairs, which provide controlled grammatical contrasts. For every BLiMP minimal pair, we identify a critical phrase, the smallest continuous span that captures the grammatical contrast and the phenomenon-relevant context. Examples whose critical phrase appears in the pre-training window are assigned to the proxy-train split; the remaining examples are assigned to the proxy-validation split. Across five grammatical phenomena, we observe delayed generalization. Analyzing pre-training checkpoints before and after generalization shows that grammatical concept vectors become more predictive of grammatical acceptability and occupy a higher-dimensional subspace after generalization. We also find that attention from the critical token to the relevant context token is concentrated in a small number of heads.
Anthology ID:
2026.aacl-long.213
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
4761–4780
Language:
URL:
https://aclanthology.org/2026.aacl-long.213/
DOI:
Bibkey:
Cite (ACL):
Sherin Muckatira, Namrata Shivagunde, Vijeta Deshpande, and Anna Rumshisky. 2026. A Pre-Training Analogue of Grokking in Language Models: Tracing Delayed Grammatical Generalization. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 4761–4780, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
A Pre-Training Analogue of Grokking in Language Models: Tracing Delayed Grammatical Generalization (Muckatira et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.213.pdf