What Is Confirmation Bias?

Glossary of Grammatical and Rhetorical Terms

Obama supporter argues with someone who wants to see his birth certificate.

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In argumentation, confirmation bias is the tendency to accept evidence that confirms our beliefs and to reject evidence that contradicts them. Also known as confirmatory bias.

When conducting research, people can make an effort to overcome confirmation bias by deliberately seeking evidence that contradicts their own viewpoints.

The concepts of perceptual defense bias and the backfire effect are related to confirmation bias.

The term confirmation bias was coined by English cognitive psychologist Peter Cathcart Wason (1924-2003) in the context of an experiment he reported on in 1960.

Examples and Observations

  • "The confirmation bias is a consequence of the way perception works. Beliefs shape expectations, which in turn shape perceptions, which then shape conclusions. Thus we see what we expect to see and conclude what we expect to conclude. As Henry David Thoreau put it, 'We hear and apprehend only what we already half know.' The truism, I'll believe it when I see it might be better stated I'll see it when I believe it.
    "The potent effect of expectations on perception was demonstrated in the following experiment. When subjects were given a drink that they thought contained alcohol, but in fact did not they experienced reduced social anxiety. However, other subjects who were told they were being given nonalcoholic beverages when they were, in fact, alcoholic did not experience reduced anxiety in social situations." (David R. Aronson, "Evidence-Based Technical Analysis." Wiley, 2007)

The Limits of Reason

  • "Women are bad drivers, Saddam plotted 9/11, Obama was not born in America, and Iraq had weapons of mass destruction: to believe any of these requires suspending some of our critical-thinking faculties and succumbing instead to the kind of irrationality that drives the logically minded crazy. It helps, for instance, to use confirmation bias (seeing and recalling only evidence that supports your beliefs, so you can recount examples of women driving 40 mph in the fast lane). It also helps not to test your beliefs against empirical data (where, exactly, are the WMD, after seven years of U.S. forces crawling all over Iraq?); not to subject beliefs to the plausibility test (faking Obama’s birth certificate would require how widespread a conspiracy?); and to be guided by emotion (the loss of thousands of American lives in Iraq feels more justified if we are avenging 9/11)." (Sharon Begley, "The Limits of Reason." Newsweek, August 16, 2010)

Information Overload

  • "In principle, the availability of a great deal of information could protect us from the confirmation bias; we could use information sources to find alternative positions and objections raised against our own. If we did that and thought hard about the results, we would expose ourselves to a valuable dialectical process of objections and replies. The problem is, though, there is too much information to pay attention to all of it. We must select, and we have a strong tendency to select according to what we believe and like to believe. But if we attend only to confirming data, we deprive ourselves of the opportunity to have well-reasoned, fair, and accurate beliefs." (Trudy Govier, "A Practical Study of Argument," 7th ed. Wadsworth, 2010)

The Backfire Effect and Affective Tipping Points

  • "The strongest bias in American politics is not a liberal bias or a conservative bias; it is a confirmation bias, or the urge to believe only things that confirm what you already believe to be true. Not only do we tend to seek out and remember information that reaffirms what we already believe, but there is also a backfire effect, which sees people doubling down on their beliefs after being presented with evidence that contradicts them.
    "So, where do we go from here? There's no simple answer, but the only way people will start rejecting falsehoods being fed to them is by confronting uncomfortable truths. Fact-checking is like exposure therapy for partisans, and there is some reason to believe in what researchers call an effective tipping point, where 'motivated reasoners' start to accept hard truths after seeing enough claims debunked over and over." (Emma Roller, "Your Facts or Mine?" The New York Times, October 25, 2016)

Perceptual Defense Bias

  • "Like other biases, the confirmation bias also has an opposite which traditionally has been termed perceptual defense bias. This process refers to the automatic discounting of disconfirming stimuli that protect the individual against information, ideas or situations that are threatening to an existing perception or attitude. It is a process that encourages the perception of stimuli in terms of the known and familiar." (John Martin and Martin Fellenz, "Organizational Behaviour and Management," 4th ed. South Western Educational Publishing, 2010)

Confirmation Bias on Facebook

  • "[C]onfirmation bias—the psychological tendency for people to embrace new information as affirming their pre-existing beliefs and to ignore evidence that doesn’t—is seeing itself play out in new ways in the social ecosystem of Facebook. Unlike Twitter—or real life—where interaction with those who disagree with you on political matters is an inevitability, Facebook users can block, mute and unfriend any outlet or person that will not further bolster their current worldview.​
    "Even Facebook itself sees the segmentation of users along political lines on its site—and synchronizes it not only with the posts users see but with the advertisements they’re shown." (Scott Bixby, "'The End of Trump': How Facebook Deepens Millennials', Confirmation Bias." The Guardian [UK], October 1, 2016)

Thoreau on Chains of Observations

  • "A man receives only what he is ready to receive, whether physically, or intellectually, or morally, as animals conceive their kinds at certain seasons only. We hear and apprehend only what we already half know. If there is something which does not concern me, which is out of my line, which by experience or by genius my attention is not drawn to, however novel and remarkable it may be, if it is spoken, I hear it not, if it is written, I read it not, or if I read it, it does not detain me. Every man thus tracks himself through life, in all his hearing and reading and observation and traveling. His observations make a chain. The phenomenon or fact that cannot in any wise be linked with the rest which he has observed, he does not observe."
    (Henry David Thoreau, "Journals," January 5, 1860)
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Nordquist, Richard. "What Is Confirmation Bias?" ThoughtCo, Feb. 16, 2021, thoughtco.com/what-is-confirmation-bias-1689786. Nordquist, Richard. (2021, February 16). What Is Confirmation Bias? Retrieved from https://www.thoughtco.com/what-is-confirmation-bias-1689786 Nordquist, Richard. "What Is Confirmation Bias?" ThoughtCo. https://www.thoughtco.com/what-is-confirmation-bias-1689786 (accessed March 24, 2023).