Confirmation Bias

Confirmation Bias Definition

Confirmation BiasConfirmation bias refers to processing information by looking for, or interpreting, information that is consistent with one’s existing beliefs. This biased approach to decision making is largely unintentional and often results in ignoring inconsistent information. Existing beliefs can include one’s expectations in a given situation and predictions about a particular outcome. People are especially likely to process information to support their own beliefs when the issue is highly important or self-relevant.

Confirmation Bias Background and History

The confirmation bias is one example of how humans sometimes process information in an illogical, biased manner. Many factors of which people are unaware can influence information processing. Philosophers note that humans have difficulty processing information in a rational, unbiased manner once they have developed an opinion about the issue. Humans are better able to rationally process information, giving equal weight to multiple viewpoints, if they are emotionally distant from the issue.

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One explanation for why humans are susceptible to the confirmation bias is that it is an efficient way to process information. Humans are bombarded with information in the social world and cannot possibly take the time to carefully process each piece of information to form an unbiased conclusion. Human decision making and information processing is often biased because people are limited to interpreting information from their own viewpoint. People need to process information quickly to protect themselves from harm. It is adaptive to rely on instinctive, automatic reflexes that keep humans out of harm’s way.

Another reason people show the confirmation bias is to protect their self-esteem. People like to feel good about themselves, and discovering that a belief that they highly value is incorrect makes people feel bad about themselves. Therefore, people will seek information that supports their existing beliefs. Another motive is accuracy. People want to feel that they are intelligent, and information that suggests one holds an inaccurate belief or made a poor decision suggests one is lacking intelligence.

Confirmation Bias Evidence

The confirmation bias is strong and widespread, occurring in several contexts. In the context of decision making, once an individual makes a decision, he or she will look for information that supports the decision. Information that conflicts with the decision may cause discomfort and is therefore ignored or given little consideration. People give special treatment to information that supports their personal beliefs. In studies examining the my-side bias, people were able to generate and remember more reasons supporting their side of a controversial issue than the opposing side. Only when a researcher directly asked people to generate arguments against their own beliefs were they able to do so. Often when people generate arguments against their beliefs, the arguments may be used selectively or even distorted or misremembered to ultimately support the existing belief. It is not that people are incapable of generating arguments that are counter to their beliefs; rather, people are not motivated to do so.

The confirmation bias also surfaces in people’s tendency to look for positive instances. When seeking information to support their hypotheses or expectations, people tend to identify information that demonstrates a hypothesis to be true rather than look for information that the opposite view is false.

The confirmation bias also operates in impression formation. If people are told what to expect from a person they are about to meet, such as the person is warm, friendly, and outgoing, people will look for information that supports their expectations. When interacting with people whom perceivers think have certain personalities, the perceivers will ask questions of those people that are biased toward supporting the perceivers’ beliefs. For example, if Maria expects her roommate to be friendly and outgoing, Maria may ask her if she likes to go to parties rather than if she often studies in the library.

Importance of Confirmation Bias

The confirmation bias is important because it may lead people to hold strongly to false beliefs or to give more weight to information that supports their beliefs than is warranted by the evidence. People may be overconfident in their beliefs because they have accumulated evidence to support them, when in reality much evidence refuting their beliefs was overlooked or ignored, which, if considered, would lead to less confidence in one’s beliefs. These factors may lead to risky decision making and lead people to overlook warning signs and other important information.

Implications of Confirmation Bias

The confirmation bias has important implications in the real world, including in medicine, law, and interpersonal relationships. Research has shown that medical doctors are just as likely to have confirmation biases as everyone else. Doctors often have a preliminary hunch regarding the diagnosis of a medical condition early in the treatment process. This hunch often interferes with considering information that may indicate an alternative diagnosis is more likely. Another related outcome is how patients react to diagnoses. Patients are more likely to agree with a diagnosis that supports their preferred outcome than a diagnosis that goes against their preferred outcome. Both of these examples demonstrate that the confirmation bias has implications for individuals’ health and well-being. In the context of law, judges and jurors often form an opinion about a defendant’s guilt or innocence before all of the evidence is known. Once an opinion is formed, new information obtained during a trial is likely to be processed according to the confirmation bias, which may lead to unjust verdicts. In interpersonal relations, the confirmation bias can be problematic because it may lead to forming inaccurate and biased impressions of others. This may result in miscommunication and conflict in intergroup settings. In addition, by treating someone according to expectations, that someone may unintentionally change his or her behavior to conform to the expectations, thereby providing further support for the perceiver’s confirmation bias.


  1. Fiske, S. T., & Taylor, S. E. (1991). .Social cognition (2nd ed.). New York: McGraw-Hill.
  2. Kunda, Z. (1990). The case for motivated reasoning. Psychological Bulletin, 108, 480-198.
  3. Nickerson, R. S. (1998). Confirmation bias: A ubiquitous phenomenon in many guises. Review of General Psychology, 2, 175-220.