The Impact of Preference Optimization Data Selection: Teaching Practical Life Skills to BabyLM

Barbora Štěpánková, Vojtěch Lanz, Jakub Szymanik


Abstract
This work investigates how the choice of preference optimization data affects small language models in the BabyLM setting. We apply SimPO to a GPT-2 model pretrained on 9M words, using 21 different 1M-word preference datasets, including UltraFeedback, which we cluster by topic, grammatical, and Reddit-based data. We show that preference datasets of the same size lead to different downstream performance. A combination of Business Content Creation, Food and Cooking, and Math and Calculations, which we refer to as the Practical Life Skills dataset, consistently improves Entity Tracking, MultiRC, and WSC tasks. The Entity Tracking gains are largely related to the model’s ability to handle cases where “nothing.” is a valid option, raising the question of whether models’ ability to abstain from selecting an answer in such cases or explicitly express uncertainty should receive more attention. Overall, we show that under strict data constraints, allocating the final 1M words to a different training objective can provide larger benefits than using them for additional pretraining.
Anthology ID:
2026.babylm-main.45
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:
575–584
Language:
URL:
https://aclanthology.org/2026.babylm-main.45/
DOI:
Bibkey:
Cite (ACL):
Barbora Štěpánková, Vojtěch Lanz, and Jakub Szymanik. 2026. The Impact of Preference Optimization Data Selection: Teaching Practical Life Skills to BabyLM. In Proceedings of the Second BabyLM Workshop, pages 575–584, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
The Impact of Preference Optimization Data Selection: Teaching Practical Life Skills to BabyLM (Štěpánková et al., BabyLM 2026)
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PDF:
https://aclanthology.org/2026.babylm-main.45.pdf