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confirmation bias


confirmation bias

Henry David Thoreau, Journals, January 5, 1860


The tendency to accept evidence that confirms our beliefs and to reject evidence that contradicts them.

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

See also:

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)

  • "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 40mph 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, Aug. 16, 2010)

  • "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)

  • "Like other biases, the confirmation bias also has an opposite which traditionally has been termed perceptual defence bias. This process refers to the automatic discounting of disconfirming stimuli that protects 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)

  • 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)
Also Known As: confirmatory bias
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