@inproceedings{zhong-etal-2026-evidence,
title = "More Evidence Is Not Always More Support: Controlled Diagnostics for Evidence Aggregation in Fact Verification",
author = "Zhong, Shaoxin and
Su, Yuchen and
Liu, Qian and
Witbrock, Michael J.",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {EMNLP} 2026",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.findings-emnlp.747/",
pages = "15724--15747",
ISBN = "979-8-89176-462-0",
abstract = "Final-context accuracy in multi-passage fact verification can hide whether an added passage contributes a new verdict-relevant fact or merely repeats evidence already present. We introduce a controlled same-prefix diagnostic derived from HoVer supporting-fact annotations to measure marginal evidence contribution. For each claim, a shared prefix covers one fact{'}s evidence while leaving another required fact absent; the next passage either repeats the covered fact or supplies the missing fact. The diagnostic contains 1,180 same-prefix pairs and an exact-repetition ladder testing whether repeated copies of one evidence sentence can change a verifier{'}s label. Supervised verifiers with similar clean F1 scores, from 0.6324 to 0.6528, differ sharply in eight-repeat flip rate, from 8.5{\%} to 30.3{\%}. Conservative pooling and natural-language-inference (NLI) scoring reduce duplicate sensitivity but give near-zero missing-fact gain, while gain-oriented systems improve gain but remain repetition-sensitive. Latent-Gated Evidence Dynamics (LGED), a compact stateful reference model, shows that low duplicate sensitivity and positive missing-fact gain can coexist. Surface controls and decision-level analyses support this diagnostic interpretation. Redundancy and reader tests extend the duplicate-sensitivity finding beyond HoVer, while prompted open-weight LLMs reveal a gap between role recognition and verdict updating."
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<abstract>Final-context accuracy in multi-passage fact verification can hide whether an added passage contributes a new verdict-relevant fact or merely repeats evidence already present. We introduce a controlled same-prefix diagnostic derived from HoVer supporting-fact annotations to measure marginal evidence contribution. For each claim, a shared prefix covers one fact’s evidence while leaving another required fact absent; the next passage either repeats the covered fact or supplies the missing fact. The diagnostic contains 1,180 same-prefix pairs and an exact-repetition ladder testing whether repeated copies of one evidence sentence can change a verifier’s label. Supervised verifiers with similar clean F1 scores, from 0.6324 to 0.6528, differ sharply in eight-repeat flip rate, from 8.5% to 30.3%. Conservative pooling and natural-language-inference (NLI) scoring reduce duplicate sensitivity but give near-zero missing-fact gain, while gain-oriented systems improve gain but remain repetition-sensitive. Latent-Gated Evidence Dynamics (LGED), a compact stateful reference model, shows that low duplicate sensitivity and positive missing-fact gain can coexist. Surface controls and decision-level analyses support this diagnostic interpretation. Redundancy and reader tests extend the duplicate-sensitivity finding beyond HoVer, while prompted open-weight LLMs reveal a gap between role recognition and verdict updating.</abstract>
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%0 Conference Proceedings
%T More Evidence Is Not Always More Support: Controlled Diagnostics for Evidence Aggregation in Fact Verification
%A Zhong, Shaoxin
%A Su, Yuchen
%A Liu, Qian
%A Witbrock, Michael J.
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Findings of the Association for Computational Linguistics: EMNLP 2026
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-462-0
%F zhong-etal-2026-evidence
%X Final-context accuracy in multi-passage fact verification can hide whether an added passage contributes a new verdict-relevant fact or merely repeats evidence already present. We introduce a controlled same-prefix diagnostic derived from HoVer supporting-fact annotations to measure marginal evidence contribution. For each claim, a shared prefix covers one fact’s evidence while leaving another required fact absent; the next passage either repeats the covered fact or supplies the missing fact. The diagnostic contains 1,180 same-prefix pairs and an exact-repetition ladder testing whether repeated copies of one evidence sentence can change a verifier’s label. Supervised verifiers with similar clean F1 scores, from 0.6324 to 0.6528, differ sharply in eight-repeat flip rate, from 8.5% to 30.3%. Conservative pooling and natural-language-inference (NLI) scoring reduce duplicate sensitivity but give near-zero missing-fact gain, while gain-oriented systems improve gain but remain repetition-sensitive. Latent-Gated Evidence Dynamics (LGED), a compact stateful reference model, shows that low duplicate sensitivity and positive missing-fact gain can coexist. Surface controls and decision-level analyses support this diagnostic interpretation. Redundancy and reader tests extend the duplicate-sensitivity finding beyond HoVer, while prompted open-weight LLMs reveal a gap between role recognition and verdict updating.
%U https://aclanthology.org/2026.findings-emnlp.747/
%P 15724-15747
Markdown (Informal)
[More Evidence Is Not Always More Support: Controlled Diagnostics for Evidence Aggregation in Fact Verification](https://aclanthology.org/2026.findings-emnlp.747/) (Zhong et al., Findings 2026)
ACL