A hallucination is when an AI model presents something wrong or invented as if it were fact – fluently worded and without reservation.
Hallucinations occur because a language model calculates probable language – not truth. When the model lacks knowledge, it does not stop; it fills the gap with the words that fit best statistically. The result looks like an answer, but it is a linguistic reconstruction of how an answer usually sounds.
The best safeguard is to steer the model's sources. In the FOCUS model, that is the Sources element: specify which sources the AI may and may not use, and ask it to say so when it does not know. That does not remove the need for fact-checking, but it makes errors fewer and easier to catch.
In practice
If you ask the AI to write a paragraph about your market, it may refer to 'a 2024 study' that was never carried out – complete with a credible institute name. If you pass that on in a newsletter or a press release, it is your organisation's name that is attached to the error.
»The AI calculates probable language – not truth. That is why we fact-check everything before it leaves the building.«
Sources is one of five elements in the FOCUS model – the whole method is in my guide to the good prompt.
The concepts in this glossary run through my AI courses and workshops, where we work with them on your own tasks.