There are ways of measuring overconfidence. People make declarations in a positive sense with a probability greater than 50%. They are overconfident in the sense that when framed that way, they assign too high a probability to the more likely outcome. This is also testable by a variety of metrics. For example, you could do a calculation where one assumes that there's a betting market and everyone here has made a $1 even bet with their confidence as given in this thread. Then, if they are overconfident in the above sense, one expects that the total result over all bets will be a loss.
Right, I'm not denying that overconfidence bias exists and is a coherent concept. I was trying to point out that when we reinterpret the predictions to be more easily verified/falsified (like I have been doing before adding some of the predictions to PredictionBook) the prediction is transformed in a way that doesn't necessarily preserve the original framing (whether positive or negative), so it would be unclear from the proposition we would be scoring whether or not the original predictor was under or overconfident.
Going through expiring predictions reminded me. Just as we did for 2010 and 2011, it's time for LessWrong to make its beliefs pay rent and give hostages to fortune in making predictions for events in 2012 and beyond.
Suggested topics include: Methods of Rationality updates (eg. "will there be any?"), economic benchmarks (price of gold has been an educational one for me this past year), medical advances (but be careful not to be too optimistic!), personal precommitments (signing up for cryonics?), being curmudgeonly about self-improvement, making daring predictions about the future of AGI, and so on.
As before, please be fairly specific. I intend to put most predictions on PredictionBook.com and it'd be nice if they weren't too hard to judge in the future.
(If you want advice on making good predictions, I've tried to write up a few useful heuristics I've learned. So far in the judging process, I've done pretty well this year, although I'm a little annoyed I got a Yemen prediction right but for the wrong reasons.)