When Auditors Fabricate: Batch-Size Degradation and Confident Hallucination in LLM Detection of Planted Document Contamination

📅 2026-09-09
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Influential: 0
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🤖 AI Summary
研究探讨了大型语言模型在检测文档中植入错误时的可靠性问题,通过不同规模的批次测试发现其性能随规模增大而急剧下降,并提出限制批次大小等改进措施。
📝 Abstract
Large language models are increasingly proposed as automated auditors of document quality, yet their reliability as detectors of planted errors is poorly characterised. We construct a contaminated corpus of 150 academic papers spanning supply chain management and medical research, injecting 450 known contaminants of three types: typographical corruption, semantic reversal, and absurd out-of-context insertion. We then evaluate Google Gemini 3.0 Pro's ability to recover a 180-contaminant answer-key subset across 60 documents under three prompting regimes of increasing scale: single document, small batch, and large batch. Detection holds at small scale and then collapses: 50% recovery on single documents, 60% on small batches, and 2.8% on large batches. The failure mode at scale is not abstention but fabrication. Rather than reporting incomplete processing, the model produced confident findings including invented contaminants of its own, absurdities such as "telepathic squirrel" and "quantum-powered toaster" that mimic the style of the planted material but do not appear in any document. Detection also varies by contamination type: absurd insertions were recovered at 75% in completed evaluations, while semantic reversals and typographical corruptions were each recovered at only 50%. The corruptions most likely to occur in the wild, plausible ones, are the ones most often missed. We conclude that LLM document auditing degrades not gracefully but deceptively, and outline the harness such systems require: bounded batch sizes, direct content injection, and mechanical verification of every reported finding against source text.
Problem

Research questions and friction points this paper is trying to address.

Large Language Models
Document Auditing
Batch-Size Degradation
Confident Hallucination
Planted Errors
Innovation

Methods, ideas, or system contributions that make the work stand out.

batch-size degradation
confident hallucination
document auditing
LLM reliability
mechanical verification
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