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Enhancing Uncertainty Modeling with Semantic Graph for Hallucination Detection
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Proposes semantic-graph (AMR-based) uncertainty modeling for LLM hallucination detection, with relation-based uncertainty propagation at sentence level and NLI-based graph calibration at passage level, evaluated on WikiBio and a new Chinese NoteSum dataset.
Problem
Uncertainty-based hallucination detection treats tokens independently and averages sentence scores, missing entity dependencies and contradictions between sentences that span multiple tokens and sentences.
Approach
Build a passage-level AMR semantic graph linking entities and sentences; propagate uncertainty from subject to object entities along graph relations with a relation-intensity penalty; and calibrate passage uncertainty with NLI contradiction probabilities between neighboring sentences in the graph.
Key results
- On WikiBio with LLaMA-30B, the method reaches 77.60 Pearson and 74.44 Spearman at passage level, versus 77.15/73.24 for FOCUS (LLaMA-30B).
- Passage-level Spearman on NoteSum improves to 61.05 versus 40.09 for the best FOCUS baseline, the reported 19.78% maximum gain.
- Ablation: removing graph-based calibration lowers WikiBio passage Pearson from 77.60 to 75.89.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use semantic-graph uncertainty modeling instead of FOCUS | Hallucination detection with LLaMA-30B · WikiBio sentence-level NonFact* | AUC: 48.80 -> 61.16 | Helped |
| Use semantic-graph uncertainty modeling instead of FOCUS | Hallucination detection with LLaMA-30B · WikiBio passage-level | Pearson: 77.15 -> 77.60 | Helped |
| Add maximum probability statistic (ablation) | Ours · WikiBio sentence-level NonFact | AUC: 86.48 -> 90.93 | Helped |
| Add probability variance statistic (ablation) | Ours · WikiBio sentence-level NonFact* | AUC: 50.94 -> 61.16 | Helped |
| Add sequence decay term (ablation) | Ours · WikiBio sentence-level NonFact* | AUC: 43.57 -> 61.16 | Helped |
| Add relation-based entity uncertainty (ablation) | Ours · WikiBio sentence-level NonFact* | AUC: 43.06 -> 61.16 | Helped |
| Add global uncertainty (ablation) | Ours · WikiBio passage-level | Pearson: 70.36 -> 77.60 | Helped |
| Add neighbor contradiction probabilities for graph calibration (ablation) | Ours · WikiBio passage-level | Pearson: 75.89 -> 77.60 | Helped |
| Replace graph-neighbor calibration with adjacent-sentence calibration (ablation) | Ours · WikiBio passage-level | Pearson: 77.60 -> 76.14 | Hurt |
| Replace graph calibration with average sentence uncertainty (ablation) | Ours · WikiBio passage-level | Pearson: 77.60 -> 75.89 | Hurt |
| Replace token uncertainty with negative log probability or token-aggregated log/entropy (ablation) | Ours · WikiBio sentence-level NonFact | AUC: 90.93 -> 82.71; 84.00; 84.19; 83.17; 84.09 | Hurt |
| Vary candidate probability count k from 3 (ablation) | Ours · WikiBio sentence-level NonFact* | AUC: 61.16; k=1: 50.94; k=5: 53.15; k=7: 49.33 | Mixed |
Surprising findings
- Removing the maximum probability term causes passage-level Pearson to collapse from 77.60 to 23.32 on WikiBio.
- Averaging sentence uncertainties and adjacent-only calibration perform similarly, indicating limits of local-only relation modeling.
Limitations
- NoteSum is a private industrial dataset and is small (200 passages), limiting reproducibility.
- Relies on AMR parsing, coreference, and entity linking pipelines whose errors propagate into the graph.
- Requires access to token probabilities and attention scores from the LLM, so it does not apply to black-box models.
Experimental setup
Datasets: WikiBio NoteSum
Benchmarks: WikiBio NoteSum
Metrics: AUC Pearson correlation Spearman correlation
Baselines: GPT-3 Uncertainties SelfCheckGPT FOCUS
Builds on: FOCUS SelfCheckGPT
Closest papers by meaning
- Zero-resource Hallucination Detection for Text Generation via Graph-based Contextual Knowledge Triples Modeling (AAAI 2025 · similarity 0.92)
- Scalable Token-Level Hallucination Detection in Large Language Models (NeurIPS 2026 · similarity 0.91)
- Joint Evaluation of Answer and Reasoning Consistency for Hallucination Detection in Large Reasoning Models (AAAI 2026 · similarity 0.90)
- HaDeMiF: Hallucination Detection and Mitigation in Large Language Models (ICLR 2025 · similarity 0.90)
- Sample Transform Cost-Based Training-Free Hallucination Detector for Large Language Models (NeurIPS 2026 · similarity 0.89)
- LLM-Check: Investigating Detection of Hallucinations in Large Language Models (NeurIPS 2024 · similarity 0.89)
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