The opposite, of course, is true. I've never been in a situation in the real world where, given a problem, I jumped immediately to a white board and felt I had to come up with a solution while being tested by people I didn't know. I have, however, had the joy of being given questions that could literally not happen, with requirements that cannot be met, all with the intent on seeing how I can think. Oh, and with no time to think, either.
If you really want to test how someone thinks over questions like that, actually give them time. Give them the questions before they show up for the interview. Then go over their solutions. They aren't under pressure, they give you a thoughtful answer, and you get a better sense of what they can do in the real world.
If you really want to test how someone thinks over questions like that, actually give them time. Give them the questions before they show up for the interview. Then go over their solutions. They aren't under pressure, they give you a thoughtful answer, and you get a better sense of what they can do in the real world.