I've always found that it demonstrates security with one's intelligence to be able to admit ignorance. People that feel like they know a lot, but don't happen to know what you're talking about will freely admit to it. OTOH it's people that feel like they don't know enough and that think they <i>should</i> know something that will pretend they do.
Beware of the other extreme.<p>I've seen organizations where this is the only "safe" answer and nothing gets done. Sometimes people say "I don't know" when they actually know enough to make a decision.
The Truth really doesn't hurt! well said. I am an intern at an organization where everyone is about two decades older than me, and there is a lot I don't know. They don't know what they can expect me to know, and I don't know what they know. I send piles of questions out to anyone who has some spare time and have not once been chastised in return.
It sometimes sounds better to phrase "I don't know" along the lines of, "Let me check on that and get back to you."<p>In Navy ROTC 'boot camp,' it was <i>verboten</i> to respond "I don't know"; the only acceptable phrasing was "I'll find out, sir." (And the cadre followed up to make sure we <i>did</i> find out.)
This really depends. All you need is a manager that doesn't accept that as an answer and you start lying. I have one like that. If I say "I don't know" he just keeps asking me the question over and over. It's surreal for sure, but I learned to nod my head and agree so he can finally leave my office and stop eating an banana with his mouth open<i>.<p></i>while talking as well