Confirmation Bias
David Kyle Johnson
After I learned about confirmation bias, I started seeing it everywhere.
Jon Ronson
Confirmation bias is the human tendency only to look for evidence that confirms what one wants to believe or what one already thinks is true.
Usually people are not too keen to look for evidence against what they want to believe is true, so they don’t. In fact, not only will people merely try to prove themselves right and never try to prove themselves wrong, but when confronted with evidence to the contrary of what they want to believe, they will actively ignore or deny it. The human propensity for self-delusion is strong.Confirmation bias greatly hinders one’s ability to find the truth. Why? Because, in all honestly, you can confirm (that is, you can find evidence for) any belief you want. Want to defend the idea that Santa is real? Millions of people believe that he is. Presents appear under millions of Christmas trees every year for which the recipients have no other explanation. Both of these facts are some evidence for Santa. That’s not to say that considering evidence for something you believe is a bad thing, but it can’t be all that you do. It shouldn’t even be most of what you do. Unless you consider the contrary evidence, you can easily fool yourself into believing something is true when it is not.
It may seem obvious that only trying to confirm your beliefs is the perfect way to delude oneself, but it’s one of the most common reasoning mistakes that people make. It’s comforting to have what we already believed confirmed, so we seek it out. Confirmation bias is why conservatives watch Fox News and liberals watch MSNBC; those channels (mostly) present only evidence that confirms their worldview of choice. When reading about religion, Christians primarily read Christian authors; atheists primarily read atheist authors.
In my experience, people are much more likely to skip right to reading the criticisms of a book they disagree with rather than actually read the book themselves.When we surround ourselves with people and views that already agree with our own, we can draw erroneous conclusions. “Everyone I know voted for Hillary. Trump must have stolen the election with voter fraud,” or “Everyone I know supports Trump. His low approval ratings must be fake news.” The fallacy is in thinking that the evidence you are aware of, the evidence you sought out because it agrees with your views, constitutes all the evidence that exists.
Unfortunately, confirmation bias may be hardwired into us. Suppose I said I was thinking of a pattern, a way to arrange three numbers, and challenged you to figure out what pattern I was thinking of. You give me three numbers and I’ll tell you whether they fit the pattern. So you say “1, 3, 5.” I say, “Yes, that fits the pattern I’m thinking of.”
So what do think the pattern is? Ascending odd numbers, right? So, instinctively, what kind of sequence would you give me next to test that hypothesis? Three more ascending odd numbers, right? Something like “3, 5, 7”? But that is exactly what you should not do. In fact, you should probably already suspect that any three ascending odd numbers will likely fit the pattern, given my first answer. Instead, you should try to disprove your theory to make sure that it’s not some other pattern that could fit “1, 3, 5.” Maybe it’s just numbers ascending by 2. Maybe it’s just any odd numbers in any order. Maybe it is ascending odd prime numbers. What you should be doing is trying to prove your “ascending odd numbers” hypothesis false, by trying to prove one of these other theories true. Give me sequences like “2, 4, 6,” “5, 3, 1,” and “11, 13, 17.” If any of these also fit, you’ll know your first hypothesis was false, and you’ll be one step closer to the truth.
The actual pattern I had in mind was “any three ascending numbers.” Notice that if all you tried to do was confirm your “ascending odd number” theory, you would give me sequences that fit the pattern all day - “21, 23, 25” or “37, 39, 41” - and yet never make any progress in figuring out the pattern.
The only way to actually figure it out is to generate theories and then try to prove them wrong. But, instinctively, we will just try to prove ourselves right - and that’s my point. Confirmation bias is ingrained; we have to learn to fight against it. If our aim is having true beliefs, we should actually try to prove what we believe is wrong.Something that goes hand in hand with confirmation bias is evidence denial. When one is confronted with sufficient evidence against some belief that one holds, what one should do is reject that belief - at least if one is concerned with truth. But that is generally not what humans do (which is evidence itself that, in general, humans are not concerned with having true beliefs). Studies have actually shown that when people are confronted with evidence that refutes positions they hold, they don’t change their mind - they dig in their heels. They believe what they previously believed even more fervently. In one study, “When Corrections Fail: The Persistence of Political Misperceptions” by Brendan Nyhan and Jason Reifler (2010), conservatives more adamantly believed that Saddam had weapons of mass destruction after being presented with direct evidence that he did not.
Ted Schick and Lewis Vaugh (2014), in their book, How to Think about Weird Things, explain evidence denial with the most obvious example I can think of - people who think that the end of the world is near and think that they can predict its occurrence. My favorite example came in 2011, when Harold Camping predicted that the rapture (the day when Christian believers are supposed to be physically taken up into heaven) would occur on May 21, 2011. When the May 21 date came and went and no one flew away to heaven, Camping didn’t admit that he was wrong. Instead, he said that it was “an invisible judgment day” where “Christ came and put the world under [spiritual] judgment.”
Conspiracy theorists are perhaps the most adept at denying evidence, for they will not only deny evidence against their theory but turn it into evidence for their theory.
Consider 9/11 “Truthers,” who argue that the Bush administration actually planned and carried out the 9/11 attacks. What about all the overwhelming evidence that it was actually planned and carried out by al Qaeda under the direction of Osama bin Laden? “All that evidence,” the conspiracy theorists will say, “was planted by the Bush administration because that’s what they want you to think.”“Yeah, that’s what they want you to think” is the perfect way to excuse away evidence against any conspiracy theory, and this actually demonstrates why conspiracy theories are fundamentally irrational. They are unfalsifia- ble; you can’t prove them wrong. To see why this makes them irrational, consider (what I call) “The Ultimate Conspiracy Theory”:
There is a clandestine group, I know not whom, working toward nefarious purposes, I know not what. All I do know is that every conspiracy theory that exists was planted by this clandestine group to throw you off the track. So, you think the moon landing was fake, the CIA killed JFK, that 9/11 was an inside job, and the illuminati control the world? Yeah, that’s what THEY want you to think.
Notice that it is tailored specifically to avoid counter-evidence; you could never prove this theory wrong. But this is the very fact that makes this theory completely irrational. It’s not that sometimes individuals or small groups don’t conspire to do bad things; of course they do. (A group successfully conspired to kill Abraham Lincoln.) But conspiracy theories have evidence denial built right into them; consequently, they are fundamentally irrational. In fact, no conspiracy theory has ever turned out to be true.
And this brings us to why the quotation that started this chapter is so cleverly ironic. Confirmation bias and evidence denial is why you start “seeing something everywhere” once you learn about it. Learn a new word, and you’ll likely hear it multiple times that day. Start thinking the number 23 has significance, and you’ll see it everywhere.
That’s because you will be looking for confirmation and ignoring the evidence to the contrary. It’s called “remembering the hits and forgetting the misses,” which feeds another common error in our thinking, called the availability error (see Chapter 21). And that’s why you will now start seeing evidence of confirmation bias and evidence denial everywhere you look.But all in all, if you really are seeking the truth - if you really want to make sure that a belief you hold is true - you should try to prove it false. After all, if all you have done is tried to prove yourself right (that is, if you have only sought out evidence for your belief), is it really any surprise that you succeeded? Anyone can find some evidence for anything. But if you have tried, genuinely, to prove yourself wrong but couldn’t - that’s a really good indication that your belief is true. Better yet, invite others to prove you wrong. The more scrutiny a belief can withstand, the more likely it is that it’s true. But if sufficient evidence is provided against your belief, don’t deny that evidence. Change your belief. As David Hume once said, “A wise man, therefore, proportions his belief to the evidence” (1993, 73).
References
Hume, David. 1993. An Enquiry concerning Human Understanding, 2nd edition, edited by Eric Stein. Indianapolis, IN: Hackett.
Nyhan, Brendan, and Jason Reifler. 2010. “When Corrections Fail: The Persistence of Political Misperceptions.” Political Behavior 32(2): 303-330.
Schick, Theodore, and Lewis Vaughn. 2014. How to Think about Weird Things: Critical Thinking for a New Age. New York, NY: McGraw-Hill.