Spotting AI hallucinations
AI makes up facts — confidently and convincingly. That's not a defect, it's the flip side of how it works. Here are the warning signs and the 30-second check that protects you.
Why AI hallucinates at all
A language model is at its core a machine that predicts the next word. It doesn't compute the truth, but the probability. That explains almost everything: why it phrases things brilliantly and invents facts in the same breath, why it never notices its own error, and why the same question gives slightly different answers twice.
A hallucination, then, isn't a glitch but the logical consequence of that. An invented quote is statistically likely — even if it never existed. Once you grasp this, you treat every AI answer as a draft, not as evidence.
Five warning signs of made-up facts
1 Overly specific details with no evidence
The more precise a claim sounds without a source attached, the sooner you check it. "Studies show that 73% …" with no study is a warning sign, not a fact.
2 Named sources, studies or statutes
Named sources look credible — and are especially often invented. Models generate something that looks like a source. Open every cited study, ruling and statute yourself.
3 Exact numbers and dates
Round, confident numbers and precise years sound reliable but are easily invented. Treat every number that matters as unverified until you've seen it.
4 Internal contradictions
If the answer says X in one place and the opposite in another, at least one place is guessed. Have the same point explained twice and compare.
5 Answers about things that don't exist
Ask about a book or a law that doesn't exist — many models will happily describe it anyway. If the AI never says "I don't know that one", suspicion is warranted.
The 30-second check
- Verify at the source: whatever has to be correct, you check at the original — not with the AI and not in a blog post.
- Demand sources: "Name the source and quote the passage verbatim." Invented claims often collapse here.
- Allow uncertainty: say in the prompt: "If you're not sure, say so." That noticeably reduces inventing.
- Cross-check: ask the same question rephrased. If the answers differ a lot, at least one is guessed.
Where hallucinations are especially expensive
Not every mistake costs the same. A clumsy headline you fix in seconds — a wrong number in a quote or an invented statute in a client letter you don't. Treat these areas as check-mandatory by default:
- Law: statutes, deadlines, rulings — always cross-check against the legal text.
- Health & finance: dosages, amounts, tax rules — never adopt unchecked.
- Quotes & sources: anything you pass on as evidence, open it first yourself.
- Numbers going outward: anything that goes to clients or into publications.
Frequently asked
What is an AI hallucination?
Why does the AI invent sources?
How do I spot a hallucination?
Are newer models free of it?
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Honesty note: this guide contains no affiliate links. Hallucinations can't be switched off, only contained — the checking routine described here doesn't replace professional verification in an individual case. For legally or medically sensitive topics: verify at the primary source or ask a professional.