[zerr]

Remember that you are talking to humans, they are flexible. You were being adversarial. If you could explain them in advance what you were trying to "read between lines", I'm pretty sure most/all of them would have changed their answers. So what you were supposing that was unfixable/permanent, apparently is fixable within 1 minute (of explanation).

[AmericanChopper]

Interviewing is by no means the perfect way to assess a candidate, but ultimately that’s what the purpose is. If I just tell candidates what I want them to say upfront, then why even bother with it at all? I want to assess what qualities they have that I want/don’t want, and what qualities they don’t have, as best I can. They don’t need to be perfect. Skills can be trained, personality characteristic much less so. People are flexible enough that some of them could spend one hour flexibly pretending to be the candidate I’m looking for, but that’s not the purpose of the exercise for me.

[zerr]

What you should care is a behavior. You should be open about what is expected. People change behavior all the time depending on the situation/group/company/context.

[AmericanChopper]

People can change the behaviour for brief periods. But who they are day in day out is going to be pretty consistent. Telling people how I would want a good candidate to behave during an interview doesn’t help at all with candidate selection. An inclination towards saying things they think people want to hear is a characteristic I’d like to select out of my candidates as well, so perhaps I’ve been killing two birds with one stone here…

[zerr]

> People can change the behaviour for brief periods.

This is a false assumption. Especially generalizing the behavior in such an adversarial setup as a job interview to a regular day to day work/life.

> Telling people how I would want a good candidate to behave during an interview

You should tell them the rules of the game. The thing is, with interviews, there are already predefined assumptions, such as not knowing something takes a point from you, so people avoid this. In your case, you are altering these assumptions without disclosing it. So people might already had changed their behavior for the interview specifically - avoiding admitting not knowing something.