Course 6, lesson 58 of 100, Ages 12+

When AI makes things up

Hallucinations and fact-checks

Like I’m 5

Sometimes AI is like a storyteller who fills the gaps with made-up bits that sound real. So we check the important facts.

The big idea

Because LLMs predict likely-sounding text, they can produce confident answers that are simply wrong, like inventing a book that doesn't exist. This is called a hallucination.

Hallucinations happen most with rare facts, exact numbers, quotes and recent events. To stay safe, check important facts in trusted sources, ask for sources, and be extra careful with health, money and legal questions.

Examples

  • Fake references: An AI invents a scientific paper title that sounds real.
  • Wrong dates: It confidently gives the wrong year for an event.
  • Checking: Searching the claim in a trusted source before using it.

How it works

  1. Sometimes a chatbot says something that sounds true but isn’t. This is called a hallucination.
  2. It happens because the AI predicts likely words. It doesn’t check facts the way you would.
  3. So check important answers with a trusted book, website or person.

Check your understanding

A chatbot tells you a surprising fact. What should you do?
Options: Check it with a trusted source; Believe it straight away; Share it with everyone.
Answer: Check it with a trusted source. AI can sound confident and still be wrong, so important facts need checking.
When are hallucinations most likely?
Options: With rare facts, exact numbers and recent events; With simple greetings; Never.
Answer: With rare facts, exact numbers and recent events. Uncommon or very specific details are where models most often slip.

Remember

AI can sound sure and still be wrong. Check the facts.

Talk about it

How can you check whether something online is true?

Go deeper

Hallucinations happen because models generate plausible text rather than look up verified facts. Grounding answers in sources, asking for citations and then checking them, and treating output as a draft all help, especially for health, legal or money questions.