When Does Training Data Matter? Dynamic Data Attribution via Window-level Influence Estimation

Jie Xu, Zihan Wu, Wenbo Pan, Yulong Ming, Xiaohua Jia


Abstract
Data attribution methods often compress the effect of each training data point into a single score, computed either at a final checkpoint or by aggregating quantities along the training trajectory. This static view hides how the contribution of a training data point changes during training. To overcome this limitation, we propose the Window-level Influence Estimator (WIE), a framework for estimating the contribution of a training data point zⱼ over a user-specified training window [t₁, t₂]. WIE models a leave-one-out-style counterfactual under a first-order linearization of SGD. An influence propagator P[t] = I − ηₜH[t] at each step models how parameter deviation is amplified or dampened by the loss landscape. Empirically, the window-level estimator reveals four distinct influence patterns: Early Influencer, Late Bloomer, Stable, Highly Fluctuating. Across multiple benchmarks, WIE improves mislabeled-data detection over the considered static and trajectory-based baselines. On BERT-IMDB with 40% label noise, WIE outperforms these baselines across the evaluated inspection ratios. On ViT-EMNIST, WIE reaches 70% recall for mislabeled data while inspecting up to 7.5× fewer candidates than TracIn requires to reach the same recall.
Anthology ID:
2026.emnlp-main.2256
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
51298–51316
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2256/
DOI:
Bibkey:
Cite (ACL):
Jie Xu, Zihan Wu, Wenbo Pan, Yulong Ming, and Xiaohua Jia. 2026. When Does Training Data Matter? Dynamic Data Attribution via Window-level Influence Estimation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 51298–51316, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
When Does Training Data Matter? Dynamic Data Attribution via Window-level Influence Estimation (Xu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2256.pdf