GPT-4 will. For example, I asked it the following:

What is the neighborhood stranger model of fluid mechanics?

It responded:

The "neighborhood stranger model" of fluid mechanics is not a recognized term or concept within the field of fluid mechanics, as of my last update in April 2023.

Now, obviously, this is a made-up term, but GPT-4 didn't confidently give an incorrect answer. Other LLMs will. For example, Bard says,

The neighborhood stranger model of fluid mechanics is a simplified model that describes the behavior of fluids at a very small scale. In this model, fluid particles are represented as points, and their interactions are only considered with other particles that are within a certain "neighborhood" of them. This neighborhood is typically assumed to be a sphere or a cube, and the size of the neighborhood is determined by the length scale of the phenomena being studied.

That is, I guess, because it doesn’t actually know anything, even things it’s accurate about, so it has no way to determine if it knows the answer or not.

Funny enough, that's one of the reasons why big companies that heavily use AI didn't initially invest heavily into LLM's. They are known to hallucinate, and often hilariously badly, so it was hard for the likes of Google and co to put their rep behind something that'll be very wrong.

As it turns out, people don't care if your AI is racist, uses heavily amounts of PII, teaches you to make napalm, or gives you incorrect health advice for serious illnesses - if it can write a doc really well, then all is forgiven.

In many ways, it's actually quite funny to project meaning and intent on AI, because it's essentially a reflection of what it was trained on - our words. What's not so funny is that the projection isn't particularly nice...

I fucking love when my students bring "chat" in as their tutor and show me the logic they followed... Bro, ChatGPT knows the correct answer, but you asked a bad question and it gave you its best guess hidden as a factual statement.

To be fair, I spend a lot of time teaching my students how to use LLMs to get the best results while avoiding "leading the witness."

The only times I've seen this is when it says their information is from like 2019 so they don't know. But this is very fringe things.

Which is how most politicians get elected.

I’ve had it tell me that it cant find anything about a question. But it’s usually when I ask for sources, frame the question as ‘is there anything online’, or otherwise ask it to do some research. If I just ask it a naked question it’ll always give an answer.

It's a gun store employee.

Well that's a surprise. Never used one so far as I know so I wouldn't know much but from what I've seen, having done my research, it's kinda helpful but not exactly the best tool for every job, I still prefer just manually going through things but hey I wouldn't know much since perhaps I just haven't come across using it in my line of work yet