There's a scene in Stanley Kubrick's comic masterpiece Dr. Strangelove in which Jack D. Ripper, an American general who's gone rogue and ordered a nuclear attack on the Soviet Union, unspools his paranoid worldview--and the explanation for why he drinks "only distilled water, or rainwater, and only pure grain alcohol"--to Lionel Mandrake, a dizzy-with-anxiety group captain in the Royal Air Force.
Ripper: "Have you ever heard of a thing called fluoridation? Fluoridation of water?"
Mandrake: "Ah, yes, I have heard of that, Jack. Yes, yes."
Ripper: "Well, do you know what it is?"
Mandrake: "No. No, I don't know what it is, no."
Ripper: "Do you realize that fluoridation is the most monstrously conceived and dangerous communist plot we have ever had to face?"
The movie came out in 1964, by which time the health benefits of fluoridation had been thoroughly established and anti-fluoridation conspiracy theories could be the stuff of comedy. Yet half a century later, fluoridation continues to incite fear and paranoia. In 2013 citizens in Portland, Ore., one of only a few major American cities that don't fluoridate, blocked a plan by local officials to do so. Opponents didn't like the idea of the government adding "chemicals" to their water. They claimed that fluoride could be harmful to human health.
Actually fluoride is a natural mineral that, in the weak concentrations used in public drinking-water systems, hardens tooth enamel and prevents tooth decay; a cheap and safe way to improve dental health for everyone. That's the scientific and medical consensus.
To which some people in Portland, echoing anti-fluoridation activists around the world, reply: We don't believe you.
We live in an age when all manner of scientific knowledge--from the safety of fluoride to the need for vaccines--faces organized and often furious opposition. Empowered by their own sources of information and their own interpretations of research, doubters have declared war on the consensus of experts.
Science doubt has become a pop-culture meme. In the recent movie Interstellar, set in a futuristic downtrodden America where
NASA has been forced into hiding, school textbooks say the Apollo moon landings were faked.
This is not surprising. Our lives are permeated by science and technology as never before. For many of us this new world is wondrous, comfortable and rich in rewards, but also more complicated and sometimes unnerving. We now face risks we can't easily analyze.
We're asked to accept, for example, that it's safe to eat food containing genetically modified organisms (GMOs) because, the experts point out, there's no evidence that it isn't safe, and no reason to believe that altering genes precisely in a lab is more dangerous than altering them wholesale through traditional breeding. But to some people, the very idea of transferring genes between species conjures up mad scientists running amok. And so, two centuries after Mary Shelley wrote Frankenstein, they talk about Frankenfood.
The world crackles with real and imaginary hazards, and distinguishing the former from the latter isn't easy. Should we be afraid that the Ebola virus, which is spread only by direct contact with bodily fluids, will mutate into an airborne super-plague? The scientific consensus says that's extremely unlikely: No virus has ever been observed to completely change its mode of transmission in humans, and there's zero evidence that the latest strain of Ebola is any different. But type "airborne Ebola" into an Internet search engine and you'll enter a dystopia where this virus has almost supernatural powers.
In this bewildering world we have to decide what to believe and how to act on that. In principle, that's what science is for. "Science is not a body of facts," says geophysicist Marcia McNutt, who once headed the U.S. Geological Survey and is now editor of prestigious journal Science. "Science is a method for deciding whether what we choose to believe has a basis in the laws of nature or not."
The scientific method leads us to truths that are less than self-evident, often mind-blowing and sometimes hard to swallow. In the early 17th Century, when Galileo claimed that the earth spins on its axis and orbits the sun, he wasn't just rejecting church doctrine. He was asking people to believe something that defied common sense, because it sure looks like the sun's going around the earth. Galileo was put on trial and forced to recant. Two centuries later, Charles Darwin escaped that fate. But his idea that all life on earth evolved from a primordial ancestor and that we humans are distant cousins of apes, whales and even deep-sea mollusks is still a big ask for a lot of people.
Even when we intellectually accept these precepts of science, we subconsciously cling to our intuitions, what researchers call our naive beliefs. A study by Andrew Shtulman of Occidental College showed that even students with an advanced science education had a hitch in their mental gait when asked to affirm or deny that humans are descended from sea animals and that the earth goes around the sun. Both truths are counterintuitive.
Shtulman's research indicates that as we become scientifically literate, we repress our naive beliefs but never eliminate them entirely. They nest in our brains, chirping at us as we try to make sense of the world.
Most of us do that by relying on personal experience and anecdotes, on stories rather than statistics. We might get a prostate-specific antigen test, even though it's no longer generally recommended, because it caught a close friend's cancer, and we pay less attention to statistical evidence, painstakingly compiled through multiple studies, showing that the test rarely saves lives but triggers many unnecessary surgeries. Or we hear about a cluster of cancer cases in a town with a hazardous-waste dump, and we assume that pollution caused the cancers. Just because two things happened together doesn't mean one caused the other, and just because events are clustered doesn't mean they're not random. Yet we have trouble digesting randomness; our brains crave pattern and meaning.
Even for scientists, the scientific method is a hard discipline. They, too, are vulnerable to confirmation bias--the tendency to look for and see only evidence that confirms what they already believe. But unlike the rest of us, they submit their ideas to formal peer review before publishing them. Once the results are published, if they're important enough, other scientists will try to reproduce them and, being congenitally skeptical and competitive, will be very happy to announce that they don't hold up. Uncertainty is inevitable at the frontiers of knowledge.
That provisional quality of science is another thing a lot of people have trouble with. To some climate-change skeptics, for example, the fact that a few scientists in the 1970s were worried about the possibility of a coming ice age is enough to raise doubts about what is now the consensus of the world's scientists: The planet's surface temperature has risen by about 1.5 degrees Fahrenheit in the past 130 years, and human actions, including the burning of fossil fuels, may have been part of the cause since the mid-20th Century.
It's clear that organizations funded in part by the fossil-fuel industry have deliberately tried to undermine the public's understanding of the scientific consensus by promoting a few skeptics. The news media gives abundant attention to such mavericks, naysayers, professional controversialists and table thumpers. The media would also have you believe that science is full of shocking discoveries made by lone geniuses. Not so. The (boring) truth is that science usually advances incrementally, through the steady accretion of data and insights gathered by many people over many years. So it has with the consensus on climate change.
But industry PR, however misleading, isn't enough to explain why so many people reject the current scientific consensus.
The "science communication problem," as it's blandly called by the scientists who study it, has yielded abundant new research into how people decide what to believe and why they so often don't accept the expert consensus. It's not that they can't grasp it, according to Dan Kahan of Yale University. In one study he asked 1,540 Americans, a representative sample, to rate the threat of climate change on a scale of zero to 10. Then he correlated that with the subjects' science literacy. He found that higher literacy was associated with stronger views at both ends of the spectrum. Science literacy promoted polarization on climate, not consensus. According to Kahan, that's because people tend to use scientific knowledge to reinforce their worldviews.
Americans fall into two basic camps, Kahan says. Those with a more "egalitarian" and "communitarian" mindset are generally suspicious of industry and apt to think it's up to something dangerous that calls for government regulation; they're likely to see the risks of climate change. In contrast, people with a "hierarchical" and "individualistic" mindset respect leaders of industry and don't like government interfering in their affairs; they're apt to reject warnings about climate change, because they know what accepting them could lead to--some kind of tax or regulation to limit emissions.
In the United States, climate change has become a litmus test that identifies you as belonging to one or the other of these two antagonistic tribes. When we argue about it, Kahan says, we're actually arguing about who we are, what our crowd is. We're thinking: People like us believe this. People like that do not believe this.
Science appeals to our rational brain, but our beliefs are motivated largely by emotion, and the biggest motivation is remaining tight with our peers. "We're all in high school. We've never left high school," says Marcia McNutt. "People still have a need to fit in, and that need to fit in is so strong that local values and local opinions are always trumping science. And they will continue to trump science, especially when there is no clear downside to ignoring science."
Meanwhile the Internet makes it easier than ever for science doubters to find their own information and experts. Gone are the days when a small number of powerful institutions--elite universities, encyclopedias and major news organizations--served as gatekeepers of scientific information. The Internet has democratized it, which is a good thing. But along with cable TV, the Web has also made it possible to live in a filter bubble that lets in only the information with which you already agree.
How to penetrate the bubble? How to convert science skeptics? Throwing more facts at them doesn't help. Liz Neeley, who helps train scientists to be better communicators at an organization called Compass, says people need to hear from believers they can trust, who share their fundamental values. Her father is a climate-change skeptic and gets most of his information on the issue from conservative media. In exasperation she finally confronted him: "Do you believe them or me?" She told him she believes the scientists who research climate change and knows many of them personally. "If you think I'm wrong," she said, "then you're telling me that you don't trust me." Her father's stance on the issue softened. But it wasn't the facts that did it. It was emotional, in this case--a father's love for his child.
If you're a rationalist, there's something a little dispiriting about all this. In Kahan's descriptions of how we decide what to believe, what we decide sometimes sounds almost incidental. Those of us in the science-communication business are as tribal as anyone else, he told me. We believe in scientific ideas not because we have truly evaluated all the evidence but because we feel an affinity for the scientific community. When I mentioned to Kahan that I fully accept evolution, he said: "Believing in evolution is just a description about you. It's not an account of how you reason."
Doubting science also has consequences, as seen in recent weeks with the measles outbreak that began in California. The people who believe that vaccines cause autism are undermining "herd immunity" to such diseases as whooping cough and measles. The anti-vaccine movement has been going strong since prestigious British medical journal, the Lancet, published a study in 1998 linking a common vaccine to autism. The journal retracted the study--much later--which was thoroughly discredited. But the notion of a vaccine-autism connection has been endorsed by celebrities and reinforced through the usual Internet filters. Anti-vaccine activist and actress Jenny McCarthy famously said on the Oprah Winfrey Show, "The University of Google is where I got my degree from.")
In the climate debate, the consequences of doubt are likely to be global and enduring. Climate-change skeptics in the United States have achieved their fundamental goal of halting legislative action to combat global warming. They haven't had to win the debate on the merits; they've merely had to fog the room enough to keep laws governing greenhouse gas emissions from being enacted.
Some environmental activists want scientists to emerge from their ivory towers and get more involved in the policy battles. Any scientist going that route needs to do so carefully, says Liz Neeley. "That line between science communication and advocacy is very hard to step back from," she says. In the debate over climate change, the central allegation of the skeptics is that the science saying it's real and a serious threat is politically tinged, driven by environmental activism and not hard data. That may not be true, and it slanders honest scientists. But the claim becomes more likely to be seen as plausible if scientists go beyond their professional expertise and begin advocating specific policies.
Scientists can be as dogmatic as anyone else--but their dogma is always wilting in the hot glare of new research. In science it's not a sin to change your mind when the evidence demands it. For some people, the tribe is more important than the latest truth; for the best scientists, the search for truth is more important than the tribe.
A version of this essay appears in National Geographic's March issue.
Editorial on 03/08/2015