I've been surprised how difficult it is for LLMs to simply answer "I don't know."
It also seems oddly difficult for them to 'right-size' the length and depth of their answers based on prior context. I either have to give it a fixed length limit or put up with exhaustive answers.
> I've been surprised how difficult it is for LLMs to simply answer "I don't know."
It's very difficult to train for that. Of course you can include a Question+Answer pair in your training data for which the answer is "I don't know" but in that case where you have a ready question you might as well include the real answer anyways, or else you're just training your LLM to be less knowledgeable than the alternative. But then, if you never have the pattern of "I don't know" in the training data it also won't show up in results, so what should you do?
If you could predict the blind spots ahead of time you'd plug them up, either with knowledge or with "idk". But nobody can predict the blind spots perfectly, so instead they become the main hallucinations.
The best pro/research-grade models from Google and OpenAI now have little difficulty recognizing when they don't know how or can't find enough information to solve a given problem. The free chatbot models rarely will, though.
This seems true for info not in the question - eg. "Calculate the volume of a cylinder with height 10 meters".
However it is less true with info missing from the training data - ie. "I have a Diode marked UM16, what is the maximum current at 125C?"
This seems fine...?
https://chatgpt.com/share/698e992b-f44c-800b-a819-f899e83da2...
I don't see anything wrong with its reasoning. UM16 isn't explicitly mentioned in the data sheet, but the UM prefix is listed in the 'Device marking code' column. The model hedges its response accordingly ("If the marking is UM16 on an SMA/DO-214AC package...") and reads the graph in Fig. 1 correctly.
Of course, it took 18 minutes of crunching to get the answer, which seems a tad excessive.
Indeed that answer is awesome. Much better than Gemini 2.5 pro which invented a 16 kilovolt diode which it just hoped would be marked "UM16".