Delta -- Contrastive Decoding Mitigates Text Hallucinations in Large Language Models

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Auteurs principaux: Huang, Cheng Peng, Chen, Hao-Yuan
Format: Preprint
Publié: 2025
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author Huang, Cheng Peng
Chen, Hao-Yuan
author_facet Huang, Cheng Peng
Chen, Hao-Yuan
contents Large language models (LLMs) demonstrate strong capabilities in natural language processing but remain prone to hallucinations, generating factually incorrect or fabricated content. This issue undermines their reliability, particularly in high-stakes domains such as healthcare and legal advisory. To address this challenge, we propose Delta, an inference-time method that reduces hallucinations without requiring model retraining or additional data. Delta works by randomly masking parts of the input prompt and contrasting the output distributions for the original and masked inputs, effectively suppressing hallucinations through inference-only computations. We evaluate Delta on context-rich question-answering benchmarks, achieving absolute improvements of approximately 3 and 6 percentage points on SQuAD v1.1 and v2, respectively, and 7 and 2 percentage points on TriviaQA and Natural Questions under-sampling decoding. Delta also improves the no-answer exact match score on SQuAD v2 by over ten percentage points, demonstrating its effectiveness in mitigating hallucinations arising from contextual ambiguity. These results highlight Delta as a computationally efficient and scalable approach for improving the reliability of LLMs in real-world applications.
format Preprint
id arxiv_https___arxiv_org_abs_2502_05825
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Delta -- Contrastive Decoding Mitigates Text Hallucinations in Large Language Models
Huang, Cheng Peng
Chen, Hao-Yuan
Computation and Language
Artificial Intelligence
Large language models (LLMs) demonstrate strong capabilities in natural language processing but remain prone to hallucinations, generating factually incorrect or fabricated content. This issue undermines their reliability, particularly in high-stakes domains such as healthcare and legal advisory. To address this challenge, we propose Delta, an inference-time method that reduces hallucinations without requiring model retraining or additional data. Delta works by randomly masking parts of the input prompt and contrasting the output distributions for the original and masked inputs, effectively suppressing hallucinations through inference-only computations. We evaluate Delta on context-rich question-answering benchmarks, achieving absolute improvements of approximately 3 and 6 percentage points on SQuAD v1.1 and v2, respectively, and 7 and 2 percentage points on TriviaQA and Natural Questions under-sampling decoding. Delta also improves the no-answer exact match score on SQuAD v2 by over ten percentage points, demonstrating its effectiveness in mitigating hallucinations arising from contextual ambiguity. These results highlight Delta as a computationally efficient and scalable approach for improving the reliability of LLMs in real-world applications.
title Delta -- Contrastive Decoding Mitigates Text Hallucinations in Large Language Models
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2502.05825