Subjects who know the actual answer to a question assign much lower probabilities they "would have" guessed for that answer, compared to subjects who must guess without knowing the answer.

( :p )

Seriously thou, maybe something from physics or math?

EDIT: Or something about sleep. Or some anti akrasia method. Or the schedule of some technological progression...

Having started of like this already, lets just make this the post that people can comment rambling lists of random subjects for inspiration?

EDIT2: For a specific math one that seems easy maybe a logarithmic curve that the value further along has to be guessed for? Might backfire if the reader is to good at math thou.

(Also, I just realized where I am and who made the request. Eeep! don't downvote me into oblivion please...)