People Who Desperately Need to Pee Are Better Liars

Want to lie more effectively? Drink a lot of water an hour before the deed. That's one takeaway from a recent study by Dr. Iris Blandón-Gitlin of California State University at Fullterton and her colleagues.
They placed research subjects in 2 groups. Members of one group drank 5 glasses of water. Members of the other drank 5 sips of water. After an hour, the subjects were asked to lie persuasively about their opinion on a topic. Reviewers were more likely to judge people who, by this point, really needed to go to the bathroom, as truthful.
These results may be the result of the inhibitory spillover effect. The need to carefully control one's bladder reinforced the need to carefully control one's expressions and mannerisms. Popular Science explains:

This result adds evidence to something called the inhibitory spillover effect. If you are already using one type of self-control, it’s easier to be self-controlled at other things. However, this only works for simultaneous tasks. Other research has found that resisting the cupcakes at the office can deplete your inhibitory control resources, making it harder to ignore that post-dinner ice cream siren song.