I hear a lot (and believe myself I suppose) that I would rather hire someone that knows how to learn than someone who currently knows thing x but can't pick up

I hear a lot (and believe myself I suppose) that I would rather hire someone that knows how to learn than someone who currently knows thing x but can't pick up and learn things on their own. But I feel like it's VERY hard to figure this out about someone. It's pretty easy to test how well someone knows a particular technology or tool (given some variance for operating in a high-pressure scenario etc.) but it seems pretty hard to tell if someone can learn new things quickly, and learn the right things. I feel like this is what algorithm tests are trying to do, but I also feel like a lot of algorithms are based on having a key insight into a problem that is, at least in my experience, pretty hard to have when you're in a room with strangers on a timer and being judged, so if you don't know the particular algorithm to apply, good luck. And also it's pretty easy to go study algorithms and hope you remember how to implement DFS if that's what they ask you in the interview. And there is some non-zero value to just knowing about different data structures and algorithms for certain types of work for sure. I don't think many of us web developer types will be implementing DFS ourselves, but I run into issues pretty often where having knowledge about different data structures and algorithms comes in handy. So I can see the appeal to doing a test like this that has nothing to do with a particular skill, where you're trying to evaluate someone's judgement and how quickly they can absorb new ideas or figure something out on the fly etc. BUT, I just think there are too many factors that can really muddy this up, and I still don't feel like there's an objective way to measure "smart and learns quickly". Even "learns quickly" is somewhat vague; I personally wouldn't expect someone to pick up, say, functional programming in an hour just by saying "go read about it." Some things take longer to learn than others. Anyway, there's no silver bullet. I still feel like we end up making pretty subjective decisions about other people when interviewing them. I don't think we're even all that aware of them ourselves. I would say though that if you're interviewing somewhere, you're getting useful information about that place by how they interview you, and so I wouldn't feel too disheartened if you feel like the interview is unfair or doesn't work for you. That's probably a good sign that you wouldn't enjoy working there anyway.