Synthetic Data Characterization via Training Dynamics

Irene Lago, Ana Ezquerro, David Vilares


Abstract
Interpreting properties of LLM-generated data is important for understanding its utility and limitations across learning tasks. In this work, we characterize synthetic data through sample-level learnability, studying variation among LLM families and scales, alongside human-written data as a reference. We generate synthetic datasets spanning single- and multi-label classification, labeling, and tree prediction tasks using LLMs from multiple families and scales. We then derive empirical data distributions from encoder training dynamics for both machine and organic data, and estimate the robustness of these distributions across encoders. Finally, we evaluate how data selection strategies based on these learnability signals affect both data sources differently.
Anthology ID:
2026.findings-emnlp.1789
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
38265–38288
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1789/
DOI:
10.18653/2026.findings-emnlp.1789
Bibkey:
Cite (ACL):
Irene Lago, Ana Ezquerro, and David Vilares. 2026. Synthetic Data Characterization via Training Dynamics. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 38265–38288, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Synthetic Data Characterization via Training Dynamics (Lago et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.1789.pdf