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How Uncertainty Can Affect Stress and Pain?

Uncertainty causes much more stress than unavoidable pain, says a new study published in Nature Communications. Uncertainty regarding the potential experience of pain is more dangerous than actually being certain of ultimately experiencing the pain. This is what has been discovered by a team from UCL. In situations where the participants of the study knew they had a 50% chance of receiving a painful electric shock, they felt more stress as opposed to how they felt in situations involving 0% and 100% chances. This is the first study that demonstrates quantified effects of uncertainty on stress.


The group of 45 participants were to play a computer game in which they had to turn over rocks, entailing the possibility of having snakes underneath. They were asked to guess whether there would be one or not; they would receive a mild electric shock on the hand if a snake was present. They would quickly learn which rocks were most likely to be hiding snakes, but the odds were changed throughout the experiments so that the uncertainty levels would change. The uncertainty level of the participants regarding the presence of a snake under any one rock was determined from their guesses by a computational model; this enabled the researchers to forecast the stress levels of the participants with respect to the level of uncertainty they faced regarding the shocks.

The results show that their uncertainty tallied with the stress levels they reported. Furthermore, the associated physiological changes (like pupil dilation and perspiration) were also monitored: the participants would sweat more and their pupil dilation would be greater when they were more uncertain.

Lead author Archy de Berker from UCL Institute of Neurology explains that it is “much worse not knowing you are going to get a shock than knowing you definitely will or won’t“. His colleague, Dr Robb Rutledge, exemplifies their findings by explaining how a job applicant would be more calm if he knew he’d fail it, or if he were confident that he would nail it, and that uncertainty is what causes anxiety. This would also apply to similar situations like waiting for information concerning train delays or for results from medical tests.

While this might sound grim at first, the findings also contain a positive side: those people whose stress levels peaked at the greatest uncertainty levels were also better able to judge whether snakes would be found under the individual rocks or not.

Apparently, stress responses being in sync with environmental uncertainty might come with benefits pertaining to survival, says senior author Dr Sven Bestmann. Following this line of reason, the right stress responses would be beneficial in gaining relevant information about dangerous, uncertain situations in one’s environment. This stress is, thus, not that bad.


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