Suspense leads to more stress than absolute doom. British researchers at the University College London found that uncertainty produced significantly more stress than inevitability when it comes to anticipating painful electric shocks.
According to results from the latest experiment, people with 50 percent chance of receiving an electric shock were the most stressed out while those with 0 percent and 100 percent chances of getting shocked were the least stressed out.
The study involved 45 participants who played computer games in which they had to flip over rocks that sometimes harbored snakes. Participants received a mildly painful electric shock every single time they flipped over a rock that contained a snake.
Over time, participants were able to learn rocks that most likely contained snakes. However, the odds of flipping over a rock containing a snake fluctuated throughout the game - creating uncertainty. A computational model of learning was used to measure participants' levels of uncertainty and physiological measurements of pupil dilation and perspiration was used to measure participants' levels of stress.
"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," said Archy de Berker, lead researcher of the current study.
"Our experiment allows us to draw conclusions about the effect of uncertainty on stress. It turns out that 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," de Berker added.
Study analysis revealed that participants whose stress levels matched uncertainty were significantly better at guessing whether or not they would receive a shock. Researchers measured this by comparing uncertainty measurements from the computational model to pupil size and level of perspiration.
In light of the latest findings, researchers said that stress can be beneficial - participants whose stress responses spiked the most at periods of greatest uncertainty were significantly better at predicting which rocks harbored snakes.
"From an evolutionary perspective, our finding that stress responses are tuned to environmental uncertainty suggests that it may have offered some survival benefit," said Dr. Sven Bestmann of the Institute of Neurology at University College London.
"Appropriate stress responses might be useful for learning about uncertain, dangerous things in the environment. Modern life comes with many potential sources of uncertainty and stress, but it has also introduced ways of addressing them. For example, taxi apps that show where a car is can offer peace of mind by reducing the uncertainty about when it will arrive. Real-time information boards at bus stops and train platforms perform a similar role, although this can be undermined by unspecified delays which cause stress for passengers and staff alike," concluded Bestmann.
The findings are published in the journal Nature Communications.
