“If we think in purely rational terms, this does not make sense: a 50% chance of a shock should be half as anxiety provoking as a 100% chance if all we care about is the threat itself,” says Tanovic. Participants show greater stress if there is a 50% chance that they might receive a shock, for example, compared to situations in which there is a 100% certainty that they will be electrocuted. In study after study, the researchers found that any element of unpredictability significantly increases people’s discomfort, despite there being no objective difference in the intensity of the shock. In a typical experiment, participants are hooked up to electrodes, capable of delivering a harmless, but slightly painful, electric shock to the skin, while the researchers measure physiological responses that tend to correlate with stress – such as the sweating of the skin or changes in pupil size. Our knowledge of uncertainty’s effects on the brain and body comes from a series of slightly sadistic studies. By understanding those mechanisms, we can learn to alleviate those feelings – and perhaps even thrive under the fear of the unknown.

Scientists including Tanovic are now making huge strides in explaining why uncertainty can be so excruciating, and delineating the knock-on consequences for our decision-making and behaviour. “Uncertainty can intensify how threatening a situation feels,” says Ema Tanovic, a psychologist with the Boston Consulting Group in Philadelphia, who has also researched the consequences of uncertainty at Yale University. For some people, a general inability to process ambiguous situations can even fuel chronic anxiety disorders.

In both scenarios – and many more – a feeling of uncertainty can bring acute discomfort. How about your feelings during dating? Would you rather that someone told you, upfront, that they didn’t want to see you again, rather than waiting for your phone to ping with a new message? Would you even risk your dignity by asking for signs of commitment at an inopportune moment? As the days go by, do you half wish that you could just know the outcome – even if it is bad news – rather than endure a single minute more of the agonising wait? Your interviewer was hard to read – there’s simply no way of guessing the outcome. Imagine you are expecting to hear back from a potential new employer about an exciting job offer.

The unknown