Being Wrong - Kathryn Schulz [63]
Actually, Elizabeth showed us only one of the many faces of confirmation bias. To see another one in action, consider a different story about astronomy, this one borrowed from Kuhn. In the West, until the mid-fifteenth century, the heavens were thought to be immutable. This theory was part of a belief system that reigned far beyond the borders of science; the idea that the heavens were eternal and unchanging (in contrast to the inconsistency and impermanence of life on earth) was a cornerstone of pre-modern Christianity. But then Copernicus came along with his idea about the earth revolving around the sun, and the Church went reeling, and suddenly much of astronomy was up for grabs. In the fifty years immediately following the Copernican revolution, Western astronomers began to observe changes in the heavens they had failed to notice for centuries: new stars appearing, others disappearing, sunspots flaring and fading out. In China, meanwhile, where the sky overhead was identical but the ideology on the ground was different, astronomers had been recording such phenomena for at least 500 years. These early Western astronomers did Elizabeth O’Donovan one better. Instead of failing to believe the counterevidence, they literally failed to see it.
Sometimes, by contrast, we see the counterevidence just fine—but, thanks to confirmation bias, we decide that it has no bearing on the validity of our beliefs. In logic, this tendency is known, rather charmingly, as the No True Scotsman fallacy. Let’s say you believe that no Scotsman puts sugar in his porridge. I protest that my uncle, Angus McGregor of Glasgow, puts sugar in his porridge every day. “Aye,” you reply, “but no true Scotsman puts sugar in his porridge.” So much for my counterevidence—and so much the better for your belief. This is an evergreen rhetorical trick, especially in religion and politics. As everyone knows, no true Christian supports legalized abortion (or opposes it), no true follower of the Qur’an supports suicide bombings (or opposes them), no true Democrat supported the Iraq War (or opposed it)…et cetera.
The Iraq War also provides a nice example of another form of confirmation bias. At a point when conditions on the ground were plainly deteriorating, then-President George W. Bush argued otherwise by, in the words of the journalist George Packer, “interpreting increased violence in Iraq as a token of the enemy’s frustration with American success.” Sometimes, as Bush showed, we look straight at the counterevidence yet conclude that it supports our beliefs instead. The NASA higher-ups responsible for the space shuttle Columbia—which disintegrated upon reentry in 2003, killing all seven astronauts onboard—demonstrated this as well: before the disaster, they consistently claimed that previous damage to the space shuttle was proof of the aircraft’s strength rather than evidence of a fatal design flaw. More generally, we all demonstrate it every time we insist that “the exception proves the rule.” Think about the claim this adage is making: that a piece of acknowledged counterevidence weighs in favor of the hypothesis it appears to weigh against.
The final form of confirmation bias I want to introduce is by far the most pervasive—and, partly for that reason, by far the most troubling. On the face of it, though, it seems like the most benign, because it requires no active shenanigans on our part—no refusal to believe the evidence, like Elizabeth O’Donovan, no dismissal of its relevance,