What d'ya know?

Or more interestingly, how do you know you know? We've all had tip-of-the-tongue experiences where you know the name of the actor or group or whatever is there but you just can't get it out. But think about this for a moment, if you can't remember it how do you know that you know? This question has implications on how we access memory or how we search for particular information, what it is it about the process that provides "clues" to the presence or not of the information we are searching for? This is not a new question, see Asher Koriat's work for some interesting papers on the subject  but has recently seen some attention and I was reminded of it reading Blink by Malcolm Gladwell where he writes about among other things first impressions and snap judgements. It seems that with these processes we are subconciously accessing information that we are not aware we possess or that we don't know we know. In this second case we can appreciate that experience allows us to draw conclusions but how do we access this experience without consciously recalling each relevant piece of information? Could there be similarities in the heuristic process at work here?