Text Attribution as Continuous Trajectories: Paired AUC Metrics and Mid-Layer Allocation-Effect Decomposition

Zihan Gu, Xinyan Zhang, TianYi Zhang, Han Zhang, Hua Zhang, Yue Hu


Abstract
Attribution aims to identify which input tokens are responsible for a language model’s predictions, yet its evaluation in NLP remains dominated by discrete Top-k removal tests that poorly reflect global importance and interaction effects. In this work, we reformulate text attribution evaluation as a continuous functional over attribution-induced trajectories and introduce two complementary AUC-based metrics tailored to autoregressive models. Perturbation AUC measures token necessity via progressive embedding-level corruption with a stable logit-based signal, while Recovery AUC evaluates sufficiency by tracking the restoration of internal representations in hidden-state space. Together, these metrics subsume Top- tests and enable principled, ordering-sensitive assessment of attribution quality. Using these diagnostics, we show that most existing attribution methods collapse to near-random rankings under continuous evaluation and fail to capture even first-order interaction effects. Motivated by this failure mode, we propose a mid-layer attribution framework that exploits a layer-wise saturation property of transformer computation to decompose attribution into information allocation and causal effect. Across multiple models and tasks, our method consistently outperforms existing baselines under both Perturbation and Recovery AUC, yielding more faithful and interaction-aware explanations of language model behavior.
Anthology ID:
2026.findings-emnlp.1628
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:
34633–34656
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URL:
https://aclanthology.org/2026.findings-emnlp.1628/
DOI:
Bibkey:
Cite (ACL):
Zihan Gu, Xinyan Zhang, TianYi Zhang, Han Zhang, Hua Zhang, and Yue Hu. 2026. Text Attribution as Continuous Trajectories: Paired AUC Metrics and Mid-Layer Allocation-Effect Decomposition. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 34633–34656, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Text Attribution as Continuous Trajectories: Paired AUC Metrics and Mid-Layer Allocation-Effect Decomposition (Gu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1628.pdf