Why and How LLMs Hallucinate: Connecting the Dots with Subsequence Associations
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Abstract (arXiv)
Large language models (LLMs) frequently generate hallucinations-content that deviates from factual accuracy or provided context-posing challenges for diagnosis due to the complex interplay of underlying causes. This paper introduces a subsequence association framework to systematically trace and understand hallucinations. Our key insight is that hallucinations arise when dominant hallucinatory associations outweigh faithful ones. Through theoretical and empirical analyses, we demonstrate that decoder-only transformers effectively function as subsequence embedding models, with linear layers encoding input-output associations. We propose a tracing algorithm that identifies causal subsequences by analyzing hallucination probabilities across randomized input contexts. Experiments show our method outperforms standard attribution techniques in identifying hallucination causes and aligns with evidence from the model's training corpus. This work provides a unified perspective on hallucinations and a robust framework for their tracing and analysis.
Key facts. Cited by 15 papers in the map (data through 14 Oct 2026). Builds on 70 of its 79 references that are in the map. First posted on arXiv 17 Apr 2025.
Builds on
70 of 79 references.
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Citing papers per year: 2025: 7; 2026: 8.
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- 2025Why Language Models Hallucinatecited by 220
- 2025CounselBench: A Large-Scale Expert Evaluation and Adversarial Benchmarking of Large Language Models in Mental Health Question Answeringcited by 21
- 2025Invisible Tokens, Visible Bills: The Urgent Need to Audit Hidden Operations in Opaque LLM Servicescited by 10
- 2025Honesty over Accuracy: Trustworthy Language Models through Reinforced Hesitationcited by 5
- 2025When Bias Pretends to Be Truth: How Spurious Correlations Undermine Hallucination Detection in LLMscited by 3
- 2025Explainability of Large Language Models: Opportunities and Challenges toward Generating Trustworthy Explanationscited by 2
- 2026Hallucination Basins: A Dynamic Framework for Understanding and Controlling LLM Hallucinationscited by 2
- 2026The Piggyback Hypothesis of Generalization: Explaining and Mitigating Emergent Misalignmentcited by 2
- 2026Actionable Hallucination Detection: Translating Latent Uncertainty into Agentic Critiquecited by 2
- 2026The Truth Stays in the Family: Enhancing Contextual Grounding via Inherited Truthful Heads in Model Lineagescited by 1
- 2026Understanding Why Language Models Hallucinate: Testing Reasoning Against Priorscited by 1
- 2025When Guessing is Rewarded: Rethinking Language Model Evaluation with Distributional Uncertainty Scoringcited by 0
3 more
- 2026SoftMatcha 2: A Fast and Soft Pattern Matcher for Trillion-Scale Corporacited by 0
- 2026When the Wrong Key Wins: Understanding and Detecting Hallucinations in LLMscited by 0
- 2026Tracing and Taming Hallucinated Terms via Subsequence-Association Filtering and Breadth-Aware Selection for LLM Query Expansioncited by 0
- 2026Tracing and Taming Hallucinated Terms via Subsequence-Association Filtering and Breadth-Aware Selection for LLM Query Expansion9 Oct 2026
- 2026When the Wrong Key Wins: Understanding and Detecting Hallucinations in LLMs14 Sep 2026
- 2026Actionable Hallucination Detection: Translating Latent Uncertainty into Agentic Critique11 Aug 2026
- 2026Understanding Why Language Models Hallucinate: Testing Reasoning Against Priors1 Jul 2026
- 2026The Truth Stays in the Family: Enhancing Contextual Grounding via Inherited Truthful Heads in Model Lineages14 Jun 2026
- 2026The Piggyback Hypothesis of Generalization: Explaining and Mitigating Emergent Misalignment4 Jun 2026
- 2026Hallucination Basins: A Dynamic Framework for Understanding and Controlling LLM Hallucinations6 Apr 2026
- 2026SoftMatcha 2: A Fast and Soft Pattern Matcher for Trillion-Scale Corpora11 Feb 2026
- 2025Honesty over Accuracy: Trustworthy Language Models through Reinforced Hesitation14 Nov 2025
- 2025When Bias Pretends to Be Truth: How Spurious Correlations Undermine Hallucination Detection in LLMs10 Nov 2025
- 2025Explainability of Large Language Models: Opportunities and Challenges toward Generating Trustworthy Explanations20 Oct 2025
- 2025When Guessing is Rewarded: Rethinking Language Model Evaluation with Distributional Uncertainty Scoring5 Oct 2025
3 more
- 2025Why Language Models Hallucinate4 Sep 2025
- 2025CounselBench: A Large-Scale Expert Evaluation and Adversarial Benchmarking of Large Language Models in Mental Health Question Answering10 Jun 2025
- 2025Invisible Tokens, Visible Bills: The Urgent Need to Audit Hidden Operations in Opaque LLM Services24 May 2025
- 2025Why Language Models Hallucinatecited by 220
- 2025CounselBench: A Large-Scale Expert Evaluation and Adversarial Benchmarking of Large Language Models in Mental Health Question Answeringcited by 21
- 2025Invisible Tokens, Visible Bills: The Urgent Need to Audit Hidden Operations in Opaque LLM Servicescited by 10
- 2025Honesty over Accuracy: Trustworthy Language Models through Reinforced Hesitationcited by 5
- 2025When Bias Pretends to Be Truth: How Spurious Correlations Undermine Hallucination Detection in LLMscited by 3
- 2026Hallucination Basins: A Dynamic Framework for Understanding and Controlling LLM Hallucinationscited by 2
- 2026The Piggyback Hypothesis of Generalization: Explaining and Mitigating Emergent Misalignmentcited by 2
- 2025When Guessing is Rewarded: Rethinking Language Model Evaluation with Distributional Uncertainty Scoringcited by 0
- 2026SoftMatcha 2: A Fast and Soft Pattern Matcher for Trillion-Scale Corporacited by 0
- 2026When the Wrong Key Wins: Understanding and Detecting Hallucinations in LLMscited by 0
- 2026Tracing and Taming Hallucinated Terms via Subsequence-Association Filtering and Breadth-Aware Selection for LLM Query Expansioncited by 0
- 2026Tracing and Taming Hallucinated Terms via Subsequence-Association Filtering and Breadth-Aware Selection for LLM Query Expansion9 Oct 2026
- 2026When the Wrong Key Wins: Understanding and Detecting Hallucinations in LLMs14 Sep 2026
- 2026The Piggyback Hypothesis of Generalization: Explaining and Mitigating Emergent Misalignment4 Jun 2026
- 2026Hallucination Basins: A Dynamic Framework for Understanding and Controlling LLM Hallucinations6 Apr 2026
- 2026SoftMatcha 2: A Fast and Soft Pattern Matcher for Trillion-Scale Corpora11 Feb 2026
- 2025Honesty over Accuracy: Trustworthy Language Models through Reinforced Hesitation14 Nov 2025
- 2025When Bias Pretends to Be Truth: How Spurious Correlations Undermine Hallucination Detection in LLMs10 Nov 2025
- 2025When Guessing is Rewarded: Rethinking Language Model Evaluation with Distributional Uncertainty Scoring5 Oct 2025
- 2025Why Language Models Hallucinate4 Sep 2025
- 2025CounselBench: A Large-Scale Expert Evaluation and Adversarial Benchmarking of Large Language Models in Mental Health Question Answering10 Jun 2025
- 2025Invisible Tokens, Visible Bills: The Urgent Need to Audit Hidden Operations in Opaque LLM Services24 May 2025