I'm not sure if anyone posseses that much will-power
So as to not render my post as merely a joke, I will now express my opinion:
I'm with Ryan on this one; any study like this would ultimately fall into the self-proclaimed scientific field of psychology, where any experiment done would be incredibly difficult to actually implement in any real-world scenarios.
As far as free will goes, I personally enjoyed reading Sam Harris' book Free Will
(a very straight-forward title). Most of the subject is merely speculatory rambling from philosophers, so it's nice to get the opinion of a neuroscientist (who also happens to have his undergraduate degree in philosophy, but oh well...).