Why AI Makes Things Up
A lawyer handed a judge six cases and none of them existed. It was not lying to him. It learned the shape of a correct answer, and the shape is all it has.
Next walkthroughIt Is Not Lying to YouThe short answer
It is not lying to you. Lying means knowing the truth and choosing to say something else, and it does not know that the thing it just handed you is false.
What it learned, from an enormous amount of writing, is the shape of a correct answer. The format, the order of the parts, the confident tone. When you ask it something it cannot look up, it produces that shape anyway, because the shape is the only thing it ever learned.
The envelope
A real legal citation has four parts: a case name, a volume number, a court and a year. Each of those has a shape. A machine that has read millions of citations can produce all four of them perfectly, in the right order, in the right format, without any of them pointing at a case that exists.
Think of an address on an envelope. Correct name, correct street format, correct city, correct postcode. Every field right. For a street that was never built. Nothing about the envelope tells you, because the envelope was only ever a format. The postman is the one who finds out.
That is also why professional care does not catch it. The invented citation arrives in exactly the voice it uses when it is right. No hedge, no I think, no slight pause. There is no tell to listen for, so listening harder does not help.
Why it guesses instead of saying it does not know
This part is not an oversight somebody forgot to fix. Researchers at OpenAI published a paper arguing that the grading itself causes it.
Picture a multiple choice test where a wrong answer costs you nothing. Four options, and you have no idea. Leave a hundred questions blank and you score zero. Guess on all hundred, and one in four comes out right by luck, so you score twenty five for knowing nothing at all.
The tests that decide which model is best mostly count how many answers came out right. They award nothing for saying I do not know. So a model that admits uncertainty scores worse than one that produces a confident guess, and the higher scoring one is the one that gets released and written about. The paper calls it an epidemic of penalising uncertain responses.
The four things worth checking
You do not have to check everything. That would make the tool useless and you would stop using it by Thursday. Four kinds of answer are different from the rest.
- Anything with a number in it. Prices, dates, percentages, dosages, distances. A number is the easiest thing for it to produce and the hardest thing for you to catch, because a wrong number looks exactly like a right one.
- Anything it says somebody else said. Quotations, studies, citations, court cases. If it names a source, treat the source as a claim rather than as evidence.
- Anything about the last few months. It learned from text that stopped at some point, and that point is further back than you think. Ask about something recent and it will usually answer anyway, out of the shape of what a recent answer sounds like.
- Anything you are about to put your name on. Not because an error is more likely there. Because an error costs more there.
The first draft, the rewrite, the email you were dreading, the thing you are only using to think out loud with: leave those alone. You will notice if they go wrong.
The thirty second check
- Ask it for the source. Not are you sure. That only tells you whether it will fold when challenged, and folding under pressure has nothing to do with whether it was right the first time. Ask where the information came from, and ask for a link you can click.
- Open the link. Actually open it. A link that does not load is your answer, and so is a link that loads something about a different subject. The most common failure is a real page that does not contain the claim attached to it, and people skip that one because the page loaded and the title looked about right.
- Search the key fact on its own. Take the number or the name or the quotation somewhere that is not the thing that just told you. If it is real it exists in more than one place. A statistic that lives only inside your chat window is not a statistic yet.
Source, open, search. You only spend those seconds on the four kinds of answer above.
Check yourself
Why is lying the wrong word for this?
Lying means knowing the truth and choosing otherwise. It does not know the answer is false, and it does not know that it does not know.
What does shaped like a correct answer mean?
It learned the format, the order of the parts and the confident tone. It can reproduce all of that without any of it pointing at something real.
Why does a confident tone not tell you anything?
The invented answer arrives in exactly the same voice as the correct one. The tone is part of the shape it learned, not a signal about the content.
Why would a model guess rather than admit uncertainty?
Because the tests that rank models count correct answers and award nothing for saying I do not know. Guessing scores higher, so the guesser is the one that ships.
Name the four kinds of answer worth checking.
Anything with a number in it. Anything it says somebody else said. Anything about the last few months. Anything you are about to put your name on.
Words used here
Why it makes things up • Token • AI agent
Go deeper
The paper behind the exam argument is Why Language Models Hallucinate, by Kalai, Nachum, Vempala and Zhang. The court filings are counted in Damien Charlotin's AI Hallucination Cases database, which held 2,217 decisions when this was filmed. If the pattern idea is new to you, start with what a pattern actually is.
What she says
A lawyer with thirty years behind him asked an AI for cases to support his client in court. It gave him six. They had names, they had dates, they had judges, they had quotations with page numbers. Every one of them was invented. That was three years ago, and it keeps happening. There is a database that counts it.
As of yesterday it holds two thousand, two hundred and seventeen court decisions where somebody filed something an AI made up. Fifteen hundred and fourteen of those are in the United States. It was about two hundred in the middle of last year.
One careless man does not explain that. This happens to people who are paying attention, in a setting where being wrong costs money, and sometimes a licence. The word everyone uses for this is hallucination. I am not going to use it, because a hallucination is something you see that is not there, and nothing here is seeing anything.
Most people say it lied to them. That is closer. It is still not right, because lying means knowing the truth and choosing to say something else. It does not know it is wrong. Here is the part that makes everything else make sense. The thing you are typing to does not have a filing cabinet. It cannot go and look something up and come back.
What it has is a very good sense of which words tend to follow which other words, built out of an enormous amount of text. When you ask a question, it produces the answer that is shaped like a correct answer. Shaped like. That is the whole thing.
A real legal citation has a case name, a volume number, a court, and a year. All four of those have a shape. The machine can produce all four of them perfectly, without any of them pointing at a case that exists. In the same way that you could write a completely convincing address on an envelope. Correct street format. Correct postcode format. For a street that was never built.
The postman is the one who finds out. And it arrives in the same confident voice it uses when it is right. That is the part that catches people. There is no wobble in the made up citation. No hedge, no I think, no slight pause. It reads exactly like the four that were real.
This next part I find genuinely interesting, and it is not a bug somebody forgot to fix. Researchers at OpenAI published a paper on exactly this question, and the argument is short enough to say in one breath. These models are graded like students sitting an exam.
Think about a multiple choice test where a wrong answer costs you nothing. Four options. You have no idea. You leave it blank, and you get zero. You guess, and you are right one time in four. So take a hundred questions you do not know. Leave every one blank, and you score zero.
Now guess on all hundred. One in four of those guesses comes out right by luck, so twenty five of them are correct. Twenty five out of a hundred, for knowing nothing. Twenty five marks. For knowing nothing. Purely for being willing to answer.
Now make that student extremely good at guessing, because it has read more than you ever will, and give it tens of millions of questions. The arithmetic does not change. Guessing wins. That is what the grading does. The tests that decide which model is best mostly count how many answers came out right.
They award nothing at all for saying, I do not know. So a model that admits uncertainty scores worse than a model that produces a confident guess. And the one that scores better is the one that gets released, written about, and bought. The paper has a phrase for it. An epidemic of penalising uncertain responses.
So when it hands you a fake source with a straight face, it is not malfunctioning. It is doing the thing it was rewarded for, for years, by every benchmark that mattered. You do not need to check everything. That would make the tool useless, and you would stop using it by Thursday.
What you need is to know which four situations are different from the rest. One. Anything with a number in it. Prices, dates, percentages, dosages, measurements, distances, how many grams of sugar are in the thing. A number is the easiest thing in the world for it to produce, and the hardest thing for you to spot as wrong, because a wrong number looks exactly like a right one.
Two. Anything it says somebody else said. Quotations, citations, studies, court cases, who wrote what and when. This is where the lawyers got caught. If it names a source, treat the source as a claim. Not as evidence. Three. Anything about the last few months.
The model learned from text that stopped at some point, and that point is further back than you think. Ask it about something recent, and it will very often answer anyway, out of the shape of what a recent answer sounds like. Four. Anything you are about to put your name on.
Sent to a client. Filed with a court. Posted publicly. Handed to your manager. Not because an error is more likely there. Because an error costs more there. Everything else, the first draft, the rewrite, the email you were dreading, the thing you are only using to think out loud with, you can leave alone. You will notice if that goes wrong.
So, how do you check. Three steps, and you can do all three while the kettle boils. Ask it for the source. Not, are you sure. Are you sure only tells you whether it will fold when challenged, and folding under pressure has nothing to do with whether it was right the first time.
Ask it for the source. Say it plainly. Where did this come from, and give me a link I can click. Open the link. Actually open it. A link that does not load, or that loads something about a different subject entirely, is your answer. This one catches most of it on its own.
Search the key fact by itself. Take the number, the name, the quotation, and go looking for it somewhere that is not the thing that just told you. If it is real, it exists in more than one place. Source. Open. Search. Thirty seconds, and you only spend them on the four things.
The people in that database were not stupid, and most of them were not lazy either. They were doing the thing the tool quietly invites everybody to do, which is to accept an answer that looks precisely like a correct answer. The habit worth building is not suspicion. Suspicion is exhausting, and it will send you back to doing everything by hand inside a week.
The habit is knowing which four things to slow down for, and spending your thirty seconds there, instead of spreading them thin across everything. The tool is not going to start telling you when it does not know. It was graded for years on how often it was right, and never once on whether it knew where its own knowledge stopped.
That part is still your job. It is a small job. It is thirty seconds. But nobody else in the process is doing it for you. Subscribe. No permission required.
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