Shortly after the University of Washington announced that the school’s fourth suspected case of the new 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 1,100 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 last flu season and 61,099 the year before.
There remains deep uncertainty about the new coronavirus’ mortality rate, with the high-end estimate that it is up to 20 times that of the flu, but some estimates go as low as 0.16 percent for those affected outside of China’s overwhelmed Hubei province. About on par with the flu.
Wasn’t there something strange, the student asked, about the extreme disparity in public reactions?
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 new coronavirus for sheer deadliness, she said, the mind has its own ways of measuring danger. And the new coronavirus disease, 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 little more than a shrug. It illustrates the unconscious biases in how human beings think about risk, as well as the impulses that often guide our responses — sometimes with serious consequences.
How Our Brains Evaluate Threat
Experts used to believe that people gauged risk like actuaries, parsing out cost-benefit analyses every time a merging car came too close or local crime rates spiked. But a wave of psychological experiments in the 1980s upended this thinking.
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 realize.
The world is full of risks, big and small. Ideally, these 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 Paul Slovic, a University of Oregon psychologist 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 airplane 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 percent 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 peoples’ experiences with it are relatively mundane.
Being told how dangerous flu is does little to change this, studies find. The brain’s risk assessment approach simply overwhelms rational calculation — a source of endless consternation to health officials trying to raise flu vaccination rates.
“We’re conditioned by our experiences,” Dr. Slovic said. “But experience can mislead us to be too comfortable with things.”
Biases, Shortcuts 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,” Daniel Kahneman, a Nobel Prize-winning economist, 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.”
In extreme cases, this can lead to a “crowding-out effect,” Dr. Bostrom said, as our emotional impulses overwhelm our cognitive faculties. The coronavirus hits a number of those triggers, often quite hard.
One is dread.
If a risk seems especially painful or disturbing, people tend to raise their estimate of how likely it is to happen to them. Reports on the coronavirus often feature upsetting imagery: unhygienic food markets, city-scale lockdowns and overcrowded hospitals.
Another trigger is a threat that is not fully understood. The less known it is, the more people may fear it, and overestimate its threat.
Threats that feel out of control, like a runaway disease outbreak, prompt a similar response, leading people to seek ways to reimpose 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. One study found that people will raise their threshold for the amount of danger they are willing to take on by a factor of one thousand if they see the risk as voluntary.
If that number sounds high, consider that driving, a danger most take on voluntarily, kills over 40,000 Americans every year. But terrorism, a threat imposed on us, kills fewer than 100.
There are countless rational 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.”
All those emotions can have real consequences.
Consider the response to the partial meltdown of the nuclear plant at Three Mile Island, in Pennsylvania, in 1979. Though the incident caused no deaths, it led to public demand to turn from nuclear power to fossil fuels whose impact on air quality, alone, is thought to cause thousands of premature deaths every year.
That calculus confounded old-school economists, who saw it as irrational. One leading nuclear power expert called it “insane.”
But it also helped give rise to new psychological models for how people measure risk.
“Our feelings don’t do arithmetic very well,” Dr. Slovic said.
That can be especially true when judging low-probability, high-risk threats like nuclear war, terrorism — or dying from the coronavirus or the flu.
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.”