NEW YORK • Shortly after the University of Washington announced that the school's fourth suspected case of the coronavirus had turned out negative, two professors, one of public policy and the other of public health, held a small dinner for students and faculty members.
Like everywhere else on campus, and in much of the world, the coronavirus was all anybody could talk about. But one of the attendees, a public health student, had had enough. Exasperated, she rattled off a set of statistics.
The virus had killed about 1,300 worldwide and infected around a dozen in the United States. Alarming, but a much more common illness, influenza, kills about 400,000 people every year, including 34,200 Americans the last flu season and 61,099 the year before.
There remains deep uncertainty about the coronavirus' mortality rate, with the high-end estimate that it is up to 20 times that of flu, but some estimates go as low as 0.16 per cent for those affected outside of China's overwhelmed Hubei province. About on a par with flu.
Wasn't there something strange, the student asked, about the extreme disparity in public reactions?
Dr Ann Bostrom, the dinner's public policy co-host, laughed when she recounted the evening. The student was right about the viruses, but not about people, said Dr Bostrom, who is an expert on the psychology of how humans evaluate risk.
While the metrics of public health might put the flu alongside or even ahead of the coronavirus for sheer deadliness, she said, the mind has its own ways of measuring danger.
And the coronavirus epidemic, named Covid-19, hits nearly every cognitive trigger we have.
That explains the global wave of anxiety. Of course, it is far from irrational to feel some fear about the coronavirus outbreak tearing through China and beyond.
But there is a lesson, psychologists and public health experts say, in the near-terror that the virus induces, even as serious threats like the flu receive a mere shrug.
Researchers found that people use a set of mental shortcuts for measuring danger. And they tend to do it unconsciously, meaning that instinct can play a much larger role than they realise.
The world is full of risks, big and small. Ideally, shortcuts help people figure out which ones to worry about and which to disregard. But they can be imperfect. The coronavirus may be a case in point.
"This hits all the hot buttons that lead to heightened risk perception," said University of Oregon psychologist Paul Slovic, who helped pioneer modern risk psychology.
When you encounter a potential risk, your brain does a quick search for past experiences with it. If it can easily pull up multiple alarming memories, then your brain concludes the danger is high.
But it often fails to assess whether those memories are truly representative.
A classic example is aeroplane crashes. If two happen in quick succession, flying suddenly feels scarier - even if your conscious mind knows that those crashes are a statistical aberration with little bearing on the safety of your next flight.
But if you then take a few flights and nothing goes wrong, your brain will most likely start telling you again that flying is safe.
When it comes to the coronavirus, Dr Slovic said, it's as if people are experiencing one report after another of planes crashing.
"We're hearing about the fatalities," he said. "We're not hearing about the 98 or so per cent of people who are recovering from it and may have had mild cases."
That tendency can cut in both directions, leading not to undue alarm but undue complacency. Though flu kills tens of thousands of Americans every year, most people's experiences with it are relatively mundane.
BIASES AND GUT INSTINCTS
The coronavirus also taps into other psychological shortcuts for assessing risk. One involves novelty: We are conditioned to focus heavily on new threats, looking for any cause for alarm. This can lead us to obsess over the scariest reports and worst-case scenarios, making the danger seem bigger still.
Maybe the most powerful shortcut of all is emotion.
Assessing the danger posed by the coronavirus is extraordinarily difficult; even scientists are unsure. But our brains act as if they have an easier way: They translate gut emotional reactions into what we believe are reasoned conclusions, even if hard data tells us otherwise.
"The world in our heads is not a precise replica of reality," Nobel Prize-winning economist Daniel Kahneman wrote in a 2011 book. "Our expectations about the frequency of events are distorted by the prevalence and emotional intensity of the messages to which we are exposed."
Threats that feel out of control, like a runaway illness outbreak, prompt a similar response, leading people to seek ways to re-impose control, for instance by hoarding supplies.
Risks that we take on voluntarily, or that at least feel voluntary, are often seen as less dangerous than they really are. Consider that driving, a danger most take on voluntarily, kills more than 40,000 Americans every year. But terrorism, a threat imposed on us, kills fewer than 100.
There are countless reasons that terrorism provokes a sharper response than traffic deaths. The same goes for a fast-spreading and little-understood outbreak versus the familiar flu.
And that is exactly the point, psychologists say. "All of these things play on our feelings," Dr Slovic said. "And that's the representation of threat for us. Not the statistics of risk, but the feelings of risk."
Our minds tend to either "round down" the probability to "basically zero" and we underreact, Dr Slovic said. Or we focus on the worst-case outcome, he said, which "gives us a strong feeling, so we overreact".