Why language models hallucinate

This seems inherently false to me. Or at least partly false. It’s reasonable to say LLMs hallucinate because they aren’t trained to say they don’t have a statistically significant answer. But there is no knowledge of correct vs incorrect in these systems. It’s all statistics so what OpenAI is describing sounds like a reasonable way to reduce hallucinations but not a way to eliminate them nor the root cause.

Is there any knowledge of "correct vs incorrect" inside you?

If "no", then clearly, you can hit general intelligence without that.

And if "yes", then I see no reason why an LLM can't have that knowledge crammed inside it too.

Would it be perfect? Hahahaha no. But I see no reason why "good enough" could not be attained.

> Is there any knowledge of "correct vs incorrect" inside you?

There is a sort of knowledge humans possess that LLMs don't (and in fact can't, without a fundamental architectural change), which is knowledge of how certain one is about something.

If you ask a human a question about how something works in biology, they will be able to give you an answer as well as a sort of "epistemic" citation (i.e. the difference between "I don't remember where exactly I originally read that, but I'm a research biologist and am quite certain that's how it works" versus "I don't remember where I read that - it's probably just something we learned about in biology class in high school. Take it with a grain of salt, as I could be misremembering.")

LLMs don't have this reflexive sense of their own knowledge - there's a fundamental divide between training data (their "knowledge") and context (their "memory") which causes them to not really be capable of understanding how they know what they know (or, indeed, whether they truly know it at all). If a model could be created where the context and training data were unified, like in a brain, I could see a more realistic path to general intelligence than what we have now.

LLMs have that knowledge. Just not nearly enough of it. Some of it leaks through from the dataset, even in base models. The rest has to be taught on purpose.

You can get an LLM to generate a list of facts that includes hallucinations - and then give that list to another instance of the same LLM, and get it to grade how certain it is of each fact listed. The evaluation wouldn't be perfect, but it'll outperform chance.

You can make that better with the right training. Or much worse, with the wrong training. Getting an LLM to be fully aware of all the limits of its knowledge is likely to be impractical, if not outright impossible, but you can improve this awareness by a lot, and set a conservative baseline for behavior, especially in critical domains.

"Fully aware of all the limits of its knowledge" is unattainable for humans too, so LLMs are in a good company.

No, LLMs don't have that knowledge. They can't inspect their own weights and examine the contents. It's a fundamental limitation of the technology.

The sort of training you're talking about is content like, "ChatGPT was trained on research papers in the area of biology. It possesses knowledge of A, B, and C. It does not possess knowledge of X, Y and Z." But this merely creates the same problem in a loop - given a question, how does the LLM -know- that its training data contains information about whether or not its training data contains information about the answer to the question? The reality is that it doesn't know, you just have to assume that it did not hallucinate that.

The problem of being unaware of these things is not theoretical - anyone with deep knowledge of a subject will tell you that as soon as you go beyond the surface level of a topic, LLMs begin to spout nonsense. I'm only a software engineer, but even I regularly face the phenomenon of getting good answers to basic questions about a technology, but then beyond that starting to get completely made-up features and function names.

> "Fully aware of all the limits of its knowledge" is unattainable for humans too

This just isn't true. Humans know whether they know things, and whether they know how they know it, and whether they know how they know how they know it, and...

Knowledge itself can contain errors, but that's not what I'm talking about. I'm not talking about never being wrong. I'm merely talking about having access to the contents of one's own mind. (Humans can also dynamically update specific contents of their own mind, but that's also not even what I'm talking about right now.) An LLMs hallucination is not just knowledge that turned out to be wrong, it is in fact knowledge that never existed to begin with, but the LLM has no way of telling the difference.