Two objections: Questions like this almost certainly do not reflect the work involved with the job you're interviewing for. Not many jobs involve sitting around

Two objections: Questions like this almost certainly do not reflect the work involved with the job you're interviewing for. Not many jobs involve sitting around solving abstract, standalone logic puzzles. Programming, for example, involves logical deduction, but in concert with a variety of other skills, and applied to software, not prose, as part of a complex development process. Maybe these type of hard questions exercise some of the same skills, but why not set tasks that involve exactly the same skills, e.g. programming assignments or some other problem taken directly from the role you're interviewing for. Second, the circumstances in which you're asking candidates to solve these problems almost certainly do not reflect those in which they will be required to work should they get the job. Nervous anxiety, unfamiliarity, strong time pressure and intense outside observation are not conductive to good performance, and are (hopefully) not part of your everyday working environment, but all are present in an interview. So when you present difficult problems, you're not just selecting for people who can solve them, you're selecting for people who can solve them in conditions that will never otherwise arise. I was able to solve the logic question in the linked article after about five minutes of head-scratching. But I am 99.9% certain that, in interview conditions, I would never have figured it out. I would have spent those five minutes of head-scratching fighting off a rising tide of panic. And the thing is, having had interviews and given interviews, I am not even particularly nervous during them, relatively speaking.