A series of 5-7 why drill down questions expanding on a particular word you don't understand or do understand.
And if they aren't quick to respond or don't answer don't know or aren't out of their depth , you know they are bullshitting.
technique borrowed from Feynman's "why magnets work video"
Even from within the first few seconds you can tell Feynman is already annoyed with the interviewer. It's possible that there is some history here: there may have already been a long run of questions and he's now become tired of it.
I know a few people who as good as constantly BS. It's a puzzle to me what drives them, and why it seems like they even don't know they are BSing. Is there some psychological explanation, I'm curious.
I was thinking about giving examples to state my point, but in fact every somewhat sane person must have had those 'WTF are they saying' moments.
Like the kind of kid that says he has a GF that lives in another city or state or even Canada lol
I wrote a program from scratch, tweaked it throughout my PhD, used it to get results for my thesis. I am quite confident in the robustness and accuracy of the program.
I couldn't explain my code to an interviewer (partially because it wasn't production-ready code, but mostly because I don't interview well). I'm glad I didn't get the job. Moved on to work with people who know I'm not a hand waver.
There are also people who struggle to answer, because reality is more complex than what they can easily convey to someone who doesn't already know the domain.
There are pros and cons to both groups.