Here’s the first problem: our brains struggle to understand risks at the extreme – either very high or very low. It’s hard to imagine what 0.00009 per cent means, so our brains think ‘very low risk’, when the risk is actually much smaller than that.
“We can’t appreciate numbers that are incredibly small. It’s really hard for our brains to make sense of them, because they did not evolve needing to make sense of numbers that small,” says Associate Professor Hassan Vally, from La Trobe University, one of Australia’s leading experts on how our brains think about risks.
Another mental shortcut: the availability heuristic. Here’s how it works.
The brain calculates probability and risk, it seems, by trying to bring to mind how many examples of a thing it can think of. The easier an idea, thought, or risk is to bring to mind, the more weight the brain gives it. If we are comparing two risks, our brains will increase the likelihood of the one that comes to mind first.
This might have been a good way for our ancestors to judge the risks of getting eaten by a lion. It is less useful now, in part because it is so strongly affected by media coverage. Our recall of events typically comes from seeing them in the media, but the media does not give equal coverage to all events.
This has all sorts of strange effects. For example, the average person is likely to believe murder occurs more than suicide, or more people perish in fires than by drowning, perhaps because of media coverage, or because murder and fire are particularly vivid images. Neither is true.
“Every day, about three people die in a car accident. Imagine if that was front-page news every day,” says Associate Professor Vally. “The reason we don’t think about car accidents is because it has become normalised. It’s part of everyday life.”
We tend to worry more about meningococcal disease, which can leave a person with an amputation, than influenza – despite influenza killing many more Australians every year.
We’re more worried about dying in a plane crash than a car crash, despite car crashes being much more common. And what about the determined campaigning we see from communities against natural-gas drilling, while in other places people live happily in towns on earthquake fault lines or built on top of volcanoes?
“When deciding whether to get the AstraZeneca jab, people are sometimes hesitant because of the incredible amount of media coverage about the risk of blood clots, the personal stories that are presented, and the rare reports from all over the world,” says Jason Tangen, associate professor of cognitive science at the University of Queensland.
“The same goes for reports of vaccine side effects. When thinking about whether to get the job or not, these examples easily flood to mind.”
Making matters worse for our brains, they tend to hunt for events to recall. It’s much easier to ‘bring to mind’ people dying from an AstraZeneca vaccine than all the people who have quietly had their lives saved by it, Associate Professor Tangen says.
AstraZeneca’s blood-clotting issues are rare and unusual, which makes them great candidates for media coverage and also easy to recall when thinking about risks.
“What doesn’t flood to mind are the many tens of thousands of people who got the jab without any ill effects whatsoever. Of course, these examples don’t come to mind, because we don’t hear about them.”
A second heuristic, known as the affect heuristic, might also be at play. This suggests people pay as much or more attention to emotional stories they may have heard than cold statistics. How your brain feels about the risk influences how likely you think it is. You can see how stories about blood clots might be more compelling to the brain than statistics about how rare they are.
You can see how easily our brains can stray from cold rational decision-making. But we don’t have to fall prey to these heuristics, says Associate Professor Tangen. Remember, they are shortcuts to allow us to make quick decisions. If we want to make high-quality, evidence-based decisions, we merely need to take our time and think through the data.
“We often find ourselves slipping into this way of thinking a lot of the time. But we can also be more deliberate,” Associate Professor Tangen says.
“If we find ourselves falling for these traps, we are smart enough to think our way out of them. Both things are going on: we’re not at the whims of all these shortcuts, we’re smarter than that. We can stop, take a breath, and be more deliberate.”
20 July 2021, HEALTH NEWS FROM SYDNEY MORNING HERALD