Would you prefer to know you were about to receive a painful electric shock, or face a 50 percent chance of the same thing? The choice seems easy. However, a study has found the possibility of pain induces more stress than the certainty.
Archy de Berker, from University College London, had 45 volunteers play a computer game in which they turned over virtual rocks, some of which had snakes underneath. The game had offline consequences, with the discovery of a snake leading to an electric shock. As players became more familiar with the game they learned to spot the sort of rock that might house a serpent. However, to make things trickier, the chances of finding a snake changed with time in unpredictable ways.
De Berker used a model to predict how confident the players could be of finding a snake, and tracked their stress levels using the well-established measures of pupil dilation and how much they sweated.
"Using our model we could predict how stressed our subjects would be not just from whether they got shocks but how much uncertainty they had about those shocks," de Berker said in a statement. "It's much worse not knowing you are going to get a shock than knowing you definitely will or won't. We saw exactly the same effects in our physiological measures – people sweat more and their pupils get bigger when they are more uncertain."
The study has been published in Nature Communications. The authors claim it is the first time the effect of uncertainty on stress has been quantified, but as far back as 1992 a study found uncertainty over the severity of an electric shock is more stressful than knowing you will receive an intense one. Earlier this year a paper in the Academy of Management Journal reported that workers are more stressed by a boss who treats them badly half the time than by one who is consistently unfair.
Moreover, the authors acknowledge that many people, particularly those prone to anxiety, are familiar with the concept. "When applying for a job, you'll probably feel more relaxed if you think it's a long shot or if you're confident that it's in the bag," said co-author Dr Robb Rutledge in the statement. "The most stressful scenario is when you really don't know. It's the uncertainty that makes us anxious. The same is likely to apply in many familiar situations, whether it's waiting for medical results or information on train delays." It seems there's a reason for the phrase "better the devil you know".
Stress can be paralyzing and damaging to health. However, there is a reason our bodies and minds have evolved to respond to pressure the way they do. The authors found that those who showed the most signs of stress when uncertain about their choices were also the most accurate in picking whether there would be a snake, and therefore a shock, under a rock they turned over.
"Appropriate stress responses might be useful for learning about uncertain, dangerous things in the environment," said senior author Dr Sven Bestmann.