Last week, Gallup announced the results of their latest survey on Americans and evolution. The numbers were a stark blow to high-school science teachers everywhere: forty-six per cent of adults said they believed that “God created humans in their present form within the last 10,000 years.” Only fifteen per cent agreed with the statement that humans had evolved without the guidance of a divine power.
What’s most remarkable about these numbers is their stability: these percentages have remained virtually unchanged since Gallup began asking the question, thirty years ago. In 1982, forty-four per cent of Americans held strictly creationist views, a statistically insignificant difference from 2012. Furthermore, the percentage of Americans that believe in biological evolution has only increased by four percentage points over the last twenty years.
Such poll data raises questions: Why are some scientific ideas hard to believe in? What makes the human mind so resistant to certain kinds of facts, even when these facts are buttressed by vast amounts of evidence?
A new study in Cognition, led by Andrew Shtulman at Occidental College, helps explain the stubbornness of our ignorance. As Shtulman notes, people are not blank slates, eager to assimilate the latest experiments into their world view. Rather, we come equipped with all sorts of naïve intuitions about the world, many of which are untrue. For instance, people naturally believe that heat is a kind of substance, and that the sun revolves around the earth. And then there’s the irony of evolution: our views about our own development don’t seem to be evolving.
This means that science education is not simply a matter of learning new theories. Rather, it also requires that students unlearn their instincts, shedding false beliefs the way a snake sheds its old skin.
To document the tension between new scientific concepts and our pre-scientific hunches, Shtulman invented a simple test. He asked a hundred and fifty college undergraduates who had taken multiple college-level science and math classes to read several hundred scientific statements. The students were asked to assess the truth of these statements as quickly as possible.
To make things interesting, Shtulman gave the students statements that were both intuitively and factually true (“The moon revolves around the Earth”) and statements whose scientific truth contradicts our intuitions (“The Earth revolves around the sun”).
As expected, it took students much longer to assess the veracity of true scientific statements that cut against our instincts. In every scientific category, from evolution to astronomy to thermodynamics, students paused before agreeing that the earth revolves around the sun, or that pressure produces heat, or that air is composed of matter. Although we know these things are true, we have to push back against our instincts, which leads to a measurable delay.
What’s surprising about these results is that even after we internalize a scientific concept—the vast majority of adults now acknowledge the Copernican truth that the earth is not the center of the universe—that primal belief lingers in the mind. We never fully unlearn our mistaken intuitions about the world. We just learn to ignore them.
Shtulman and colleagues summarize their findings:
When students learn scientific theories that conflict with earlier, naïve theories, what happens to the earlier theories? Our findings suggest that naïve theories are suppressed by scientific theories but not supplanted by them.
While this new paper provides a compelling explanation for why Americans are so resistant to particular scientific concepts—the theory of evolution, for instance, contradicts both our naïve intuitions and our religious beliefs—it also builds upon previous research documenting the learning process inside the head. Until we understand why some people believe in science we will never understand why most people don’t.
In a 2003 study, Kevin Dunbar, a psychologist at the University of Maryland, showed undergraduates a few short videos of two different-sized balls falling. The first clip showed the two balls falling at the same rate. The second clip showed the larger ball falling at a faster rate. The footage was a reconstruction of the famous (and probably apocryphal) experiment performed by Galileo, in which he dropped cannonballs of different sizes from the Tower of Pisa. Galileo’s metal balls all landed at the exact same time—a refutation of Aristotle, who claimed that heavier objects fell faster.
While the students were watching the footage, Dunbar asked them to select the more accurate representation of gravity. Not surprisingly, undergraduates without a physics background disagreed with Galileo. They found the two balls falling at the same rate to be deeply unrealistic. (Intuitively, we’re all Aristotelians.) Furthermore, when Dunbar monitored the subjects in an fMRI machine, he found that showing non-physics majors the correct video triggered a particular pattern of brain activation: there was a squirt of blood to the anterior cingulate cortex, a collar of tissue located in the center of the brain. The A.C.C. is typically associated with the perception of errors and contradictions—neuroscientists often refer to it as part of the “Oh shit!” circuit—so it makes sense that it would be turned on when we watch a video of something that seems wrong, even if it’s right.
This data isn’t shocking; we already know that most undergrads lack a basic understanding of science. But Dunbar also conducted the experiment with physics majors. As expected, their education enabled them to identify the error; they knew Galileo’s version was correct.
But it turned out that something interesting was happening inside their brains that allowed them to hold this belief. When they saw the scientifically correct video, blood flow increased to a part of the brain called the dorsolateral prefrontal cortex, or D.L.P.F.C. The D.L.P.F.C. is located just behind the forehead and is one of the last brain areas to develop in young adults. It plays a crucial role in suppressing so-called unwanted representations, getting rid of those thoughts that aren’t helpful or useful. If you don’t want to think about the ice cream in the freezer, or need to focus on some tedious task, your D.L.P.F.C. is probably hard at work.
According to Dunbar, the reason the physics majors had to recruit the D.L.P.F.C. is because they were busy suppressing their intuitions, resisting the allure of Aristotle’s error. It would be so much more convenient if the laws of physics lined up with our naïve beliefs—or if evolution was wrong and living things didn’t evolve through random mutation. But reality is not a mirror; science is full of awkward facts. And this is why believing in the right version of things takes work.
Of course, that extra mental labor isn’t always pleasant. (There’s a reason they call it “cognitive dissonance.”) It took a few hundred years for the Copernican revolution to go mainstream. At the present rate, the Darwinian revolution, at least in America, will take just as long.
Illustration courtesy of Hulton Archive/Getty Images.