That's right Bossk...Each of the three has to entertain the possibility that the other two raised their hands in response to each other. ...or to say it better, regardless of what he has on his head, he knows the other two people can see at least one dot.

Here's the out of the box answer you're looking for, Bossk:
Since this is a job interview, it has to be fair. Therefore, all three of them must be answering the same question, so they all must have the same thing.

BUT, there's a real answer. Here's a hint if you want it (skip if you don't)

It is important for whoever answers to know that all three of them are skilled in logic.