How you speculate about things you know nothing about is a far better gauge of problem solving skills than asking questions about an area where you can rely on learned facts, in my opinion.
It's not going to be accurate, but that is not the point. The point is whether you return a blank stare or start trying to reason and analyse the problem.
Sure, you might end up with any number of "I have no idea what the right value for this is - if it wasn't an interview, I'd look it up, but for the sake of argument let's say the value is X". That's fine. Your ability to make that leap and continue is more important than the right result (so is your ability to recognise and admit that you don't know and are substituting guesses)
Do you think speculation on things that are an inferential step[1](or a couple of steps) away from things you currently know could be a gauge of a person's innate intelligence?
Intelligence is required to make inferences. Assuming a common starting ground, a person who could make the most logical inferences from it to explain a result would suggest that he's smarter. I do not claim to say a person who makes 10 good points is less smart than someone who makes 11 good points. But he surely you can agree that a person who is able to make 0 inferences is likelier to be less intelligent than someone who makes a hundred.
> Do you think speculation on things that are an inferential step[1](or a couple of steps) away from things you currently know could be a gauge of a person's innate intelligence?
No, I do not. It introduces a large capacity for things to go wrong, and it is very difficult for the interviewer to separate themselves from process. Speculative development is a road marked by dozens or hundreds of failed efforts before you hit on success. Either the interviewee happens to hit upon one of the few "correct" answers in the time available -- password guessing -- or some tolerance of wrong answers is to be accepted. But it is quite difficult to differentiate bad speculation from fruitless speculation, in a way that usefully differentiates candidates based on capability.
