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Patterns and proofs

The science of dread: anticipating pain makes it worse

Rather be in the waiting room? U.S. Navy

For most people, a chocolate today is better than one tomorrow. Economists refer to this as “future discounting”, where we prefer to have nice things now rather than wait and unpleasant things later rather than now.

But this isn’t always the case in reality. When it comes to a potentially painful experience, like having an operation, many people choose to get it over and done with rather than put it off.

In a new paper published in PLOS Computational Biology, researchers from Imperial College London and University College London explore how this reluctance to wait for pain – a feeling commonly known as dread – changes depending on the timing of the painful event. The researchers wanted to know if dread is worse when pain is more delayed.

The study involved a series of experiments in which pain took the form of brief electric shocks to the back of the hand of 35 participants. Over the course of the experiments, participants could choose to receive shocks soon, or delay them by a certain amount of time, which could range from a few seconds to a quarter of an hour.

A minority chose to wait and receive the shocks further into the future. But 71% of participants opted to receive pain sooner, even if meant it would be worse, because, in half of the experiments, choosing earlier pain resulted in more shocks.

The researchers also compared the size of the delay and the probability a participant would choose the later shock. They found the relationship between the two was best described by what they called “exponential dread”: the bigger the delay, the more likely it was the person would opt for the earlier shock.

The shock experiments were relatively brief, so researchers also looked at what happens when people can delay a painful experience much further into the future. The participants were given a hypothetical scenario, in which they had to schedule an appointment for a painful dental procedure. They were told they could have the procedure “today”, or at a fixed later time. This time varied between participants: it could be 1, 5, 13, 32, 89 or 237 days.

Once again, the participants’ choices suggested dread increases exponentially as people approach a painful event:

Adapted from PLOS Computational Biology

These results build on previous work, such as a 2006 study which assumed people experienced constant amount of dread over time, rather than having dread increase with the size of the delay. There are, however, still some questions that remain unanswered.

First, how does dread scales with time? The researchers looked at events that occur over minutes and weeks, but can the same patterns be found at other timescales?

Second, what causes us to experience dread in the first place? The researchers suggest a couple of potential explanations. It might be that the brain processes designed to prepare us for a painful experience overrule other types of behaviour, even if this other behaviour could be beneficial. Alternatively, dread could be a form of “stimulus substitution”, whereby the anticipation of pain triggers the same responses that we experience during an actual pain event.

Even if the causes of dread remain elusive, understanding how people deal with the anticipation pain could help in a number of fields. In particular, it could be useful when assessing options about a potentially painful future event, whether that event is an electric shock, a medical procedure, or your girlfriend finding out you’ve eaten all the chocolates.

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