Planning to tell your boss how much you appreciate him and how lucky you are to work for him? Try drinking lots of water one hour before your meeting, and don’t go to the bathroom. Chances are, he’ll find you more credible! Everyone knows that when you desperately need to urinate it can be complicated to focus on anything else. A recent study by American psychologists showed an interesting secondary effect: waiting to urinate can make us better liars. How can the art of lying be linked to our bladders? Why do we become more convincing when our bladders are full? The following explanation is of public interest.

Life in our society depends on our capacity to resist our basic needs and impulses; indeed we have to restrain ourselves from certain thoughts, feelings and behaviors. The control center of social inhibitions, or self-control, is mainly found in the right inferior frontal cortex, and studies in cognitive psychology show an increased cerebral activity in this area when we lie. Lying requires a greater mental effort than telling the truth because we need to inhibit automatic thoughts (thoughts about truth and reality), but we also need to monitor our own behavior along with the behavior of the person we’re speaking to.

From 2000-2010, a series of experiments suggested that the inhibition of motor activity (having a full bladder for example) could increase emotional inhibitions. A more recent study published in Consciousness and Cognition on the urge to urinate and inhibition, and led by Iris Blandon-Gitlin from the University of California, is described below.

11 participants had to drink 5 large glasses of water (700ml) while 11 others drank 5 small mouthfuls of 50ml. Both groups of participants were questioned after a period of 45 minutes. The questions were related to social and moral issues; in particular the death sentence, control of fire arms, and the rights of homosexuals. The researchers chose two opinions that were strongly held by each participant, and on which they had to lie. All of the participants were filmed during questioning to note behavioral signals associated with lying. The result was the same for both sessions of observation: the participants who were desperate to empty their bladders displayed less behavioral signals of lying, increased cognitive control, and longer and more complicated explanations. They also appeared more confident, spontaneous and genuine than participants with an empty bladder. The experiment showed it was more difficult to detect lying in those with a full bladder as opposed to those who didn’t have to resist the urge to urinate.

The study involved too few participants to consider as scientific fact what psychologists refer to as “ISE: inhibitory spillover effect,” and the question remains as to whether our efforts not to urinate really improve our capacity for self-control and make us better liars.

Despite scientific precautions, certain professions could be greatly interested by this research.