Dense Supervision, Gentle Decay: Curriculum-Guided Rebalancing of ELECTRA-Style RTD and MLM for Small-Data Pretraining

Aftab Hossain Mikat, Tamjid Hasan Fahim


Abstract
When training data is very limited, the way different training signals are weighted over time can strongly affect what a model learns. We study hybrid replaced-token detection (RTD) and masked language modeling (MLM) pretraining under the BabyLM 2026 Strict-Small budget. We train five single-seed DeBERTa-v2 models along three curriculum axes: objective scheduling, masking policy, and data order. The primary system, bgb-decay, retains generator MLM, discriminator RTD, and auxiliary discriminator MLM throughout training while reducing the RTD coefficient in stages. We compare it with a matched fixed-RTD reference, a variant that adds easy-to-hard data ordering and adaptive auxiliary masking, and two stronger RTD-to-MLM handoff schedules with whole-word and adaptive masking. Among the five runs, bgb-decay achieves the best overall balance, while the more aggressive variants gain more on some tasks but drop more on others. Training diagnostics reveal a trade-off between replacement discrimination and auxiliary vocabulary prediction: under fixed high RTD weighting, RTD gradients are larger and nearly orthogonal to auxiliary-MLM gradients, while staged decay preserves RTD but shifts late optimization toward MLM. These results suggest that gradual objective rebalancing is a promising direction for small-data pretraining.
Anthology ID:
2026.babylm-main.66
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:
859–874
Language:
URL:
https://aclanthology.org/2026.babylm-main.66/
DOI:
Bibkey:
Cite (ACL):
Aftab Hossain Mikat and Tamjid Hasan Fahim. 2026. Dense Supervision, Gentle Decay: Curriculum-Guided Rebalancing of ELECTRA-Style RTD and MLM for Small-Data Pretraining. In Proceedings of the Second BabyLM Workshop, pages 859–874, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Dense Supervision, Gentle Decay: Curriculum-Guided Rebalancing of ELECTRA-Style RTD and MLM for Small-Data Pretraining (Mikat & Fahim, BabyLM 2026)
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PDF:
https://aclanthology.org/2026.babylm-main.66.pdf