Learning! Free Will vs. The Call of Nature
While philosophers and scientists will argue over whether or not (or to what degree) free will actually exists, but you ask the Average Pat walking down the street and he/she'll say "hells yes, I have free will!"
Or will they?
Turns out, it depends.
A recent study shows that people will report believing they have less free will when they have to go to the bathroom, or when they are feeling frisky. That's right, if you have to pee or are desirous of some good-time-action, suddenly you don't believe we have so much free will anymore. When your body is calling the shots your brain realizes that it can only control so much.
Same goes if you're tired. Interestingly, hunger did not have the same effect. Could be because in Western society, hunger just means you have more choices to make - what you'll eat, where you'll eat it, if you'll make it yourself, and so on.
Source: BPS Research Digest.