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What Is Hallucination?
AI Hallucination
An AI hallucination occurs when a language model generates information that sounds confident and plausible but is factually incorrect or entirely fabricated. LLMs don't 'know' facts — they predict likely text sequences, which sometimes produces convincing nonsense.
How Hallucination Works
Common hallucinations: citing non-existent research papers, generating plausible but wrong code, inventing API endpoints that don't exist, or confidently stating incorrect dates or statistics. The model has no concept of truth — it generates probable-sounding text.
Mitigation strategies: RAG (ground responses in real documents), temperature reduction (less creative = fewer hallucinations), chain-of-thought prompting, citation requirements, and human review. No approach eliminates hallucinations entirely.
Key Concepts
- Confabulation — When the model fills gaps in knowledge with plausible but fabricated information — a core hallucination mechanism
- Grounding — Providing real documents or data in the prompt so the model bases responses on facts rather than imagination
- Uncertainty Calibration — Well-calibrated models express uncertainty when they're unsure — poorly calibrated ones state fabrications confidently
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Frequently Asked Questions
Can hallucinations be eliminated?
Not completely with current technology. They can be significantly reduced through RAG, better prompting, temperature tuning, and human review — but LLMs can always generate incorrect information.
Why do LLMs hallucinate?
LLMs are trained to predict the next likely token, not to determine truth. They don't have a fact database — they have statistical patterns. When the training data doesn't cover a topic well, the model extrapolates plausibly but incorrectly.