The Privacy-Hallucination Tradeoff in Differentially Private Language Models
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Abstract (arXiv)
Both privacy and factual accuracy are paramount in high-stakes domains like healthcare. Concerningly, we uncover and investigate a privacy-hallucination tradeoff in differentially private (DP) language models. First, we empirically show that models pre-trained or fine-tuned with DP tend to produce more hallucinations than non-DP counterparts, with increased severity as the privacy budget grows stricter. Second, we investigate model properties driving this tradeoff, demonstrating that DP mechanisms flatten output distributions, potentially redistributing probability mass toward factually incorrect alternatives. Third, through experiments where we control fact frequency in training data, we characterize how information frequency can reduce hallucination risks in DP models. Overall, our findings underscore the need for more nuanced privacy-preserving interventions that offer rigorous privacy guarantees without compromising factual accuracy.
Key facts. No citing papers in the map yet (data through 14 Oct 2026). Builds on 72 of its 92 references that are in the map. First posted on arXiv 31 Aug 2026.
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References · 72
- 2021LoRA: Low-Rank Adaptation of Large Language Modelscited by 14,380
- 2016Deep Learning with Differential Privacycited by 2,728
- 2020Extracting Training Data from Large Language Modelscited by 2,189
- 2019Language Models as Knowledge Bases?cited by 1,936
- 2023FActScore: Fine-grained Atomic Evaluation of Factual Precision in Long Form Text Generationcited by 1,282
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- 2024Negative Preference Optimization: From Catastrophic Collapse to Effective Unlearningcited by 504
- 2022Knowledge Unlearning for Mitigating Privacy Risks in Language Modelscited by 437
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- 2021SummaC: Re-Visiting NLI-based Models for Inconsistency Detection in Summarizationcited by 407
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- 2019Differential Privacy Has Disparate Impact on Model Accuracycited by 316
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- 2021QAFactEval: Improved QA-Based Factual Consistency Evaluation for Summarizationcited by 236
- 2023Fine-tuning Language Models for Factualitycited by 221
- 2025Why Language Models Hallucinatecited by 220
- 2023Beyond Memorization: Violating Privacy Via Inference with Large Language Modelscited by 175
- 2024Long-form factuality in large language modelscited by 155
- 2023How to DP-fy ML: A Practical Guide to Machine Learning with Differential Privacycited by 153
- 2021Hallucinated but Factual! Inspecting the Factuality of Hallucinations in Abstractive Summarizationcited by 129
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- 2022Synthetic Text Generation with Differential Privacy: A Simple and Practical Recipecited by 108
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- 2024The Dawn After the Dark: An Empirical Study on Factuality Hallucination in Large Language Modelscited by 88
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- 2024Evaluations of Machine Learning Privacy Defenses are Misleadingcited by 36
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- 2025On Linear Representations and Pretraining Data Frequency in Language Modelscited by 23
- 2025Scaling Laws for Differentially Private Language Modelscited by 22
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