eTracer: Polarity-Aware Evidence Grounding

Bohao Chu, Qianli Wang, Hendrik Damm, Shuning Zhang, Hui Wang, Andrea Papenmeier, Georg Lodde, Elisabeth Livingstone, Christoph M. Friedrich, Norbert Fuhr


Abstract
Evidence grounding makes generated content verifiable by linking statements to their sources. However, effective verifiability requires two properties that existing methods fail to jointly provide: *verification granularity*, the ability to localize fine-grained evidence for each statement, and *verification completeness*, the ability to capture both support and contradiction. Existing methods either operate at granularities too coarse for rapid inspection or are support-only. We formalize *polarity-aware evidence grounding*: linking each response sentence to its contextual evidence with a supporting, contradicting, or irrelevant label. We construct **eTracer-Bench**, a human-annotated benchmark with 7,905 supporting and contradicting sentence pairs across seven domains, covering both explicit and implicit contradictions. We further propose **eTracer**, a post-hoc framework whose context-aware signed scorer recovers the full evidence map in a single forward pass per response, with localization and polarity emerging jointly from one mechanism. **eTracer** achieves the best overall Citation F1 of **82.39**, driven by a Contradict F1 of **89.20**. A pre-registered within-subjects user study (n = 30) shows that polarity-aware grounding nearly doubles contradiction detection over the document-level baseline (**27.9% → 51.9%**, Cohen’s d = 0.82, p = 0.0003), and suggests a false-completeness bias under which support-only grounding fails to improve over this baseline (**23.4% vs. 27.9%**). Dataset and code: https://github.com/chubohao/eTracer.
Anthology ID:
2026.emnlp-main.314
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:
7224–7253
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URL:
https://aclanthology.org/2026.emnlp-main.314/
DOI:
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Cite (ACL):
Bohao Chu, Qianli Wang, Hendrik Damm, Shuning Zhang, Hui Wang, Andrea Papenmeier, Georg Lodde, Elisabeth Livingstone, Christoph M. Friedrich, and Norbert Fuhr. 2026. eTracer: Polarity-Aware Evidence Grounding. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 7224–7253, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
eTracer: Polarity-Aware Evidence Grounding (Chu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.314.pdf