Why we interpret information favoring our existing beliefs.


Confirmation Bias

, explained.

What is Confirmation Bias?

Confirmation bias describes each person’s underlying tendency to notice, focus on, and provide greater credence to evidence that seems to confirm his or her existing beliefs.


Confirmation bias is a form of self-deception that arises when a person fails to interpret facts in an objective way. Since everyone has certain patterns of thought and behavior, detecting confirmation bias can be difficult.

Under experimental conditions, decision-makers have a tendency to actively seek out and assign greater value to evidence that supports the conclusions they began with rather than entertaining new ones. This can be considered a form of bias in evidence collection.

Everyone would like to believe that their positions on key issues arise from careful consideration of the facts at hand. Once a belief is formed, however, many individuals are rarely in a position to seek out and consider opposing viewpoints in a respectful environment.

Not only that, but people are far less likely to examine core beliefs that they consider intrinsic to their identity. These beliefs may have been developed years ago and without a rigorous review of the facts – yet confirmation bias helps to ensure that they remain unchallenged.

Confirmation bias is encountered in many situations involving important or “controversial” topics. It may be considered one of the core reasons why people often do not seem to change their beliefs on political or religious topics in response to new information.

Some research has suggested that the modern media environment plays a role in reinforcing confirmation bias. For example, getting news from social media often means switching topics more quickly and focusing on each source for a shorter amount of time.

As a result, people are more likely to invest their limited attention in already-preferred sources.

Confirmation bias was known to the ancient Greeks and written about by the classical historian Thucydides, who observed that people “entrust to careless hope” what they wish to be true. By contrast, they “use […] reason to thrust aside” what they do not.

Modern studies have repeatedly underscored the power of confirmation bias.

Confirmation bias causes people to overlook pivotal information both in leadership and in everyday life. A voter might stand by a candidate “right or wrong” while dismissing emerging facts about the candidate’s behavior, for example. A business executive might fail to investigate a new opportunity because of preconceived notions from a past engagement with similar ideas.


Researchers at Stanford University carried out a major study exploring the psychological dynamics of this bias. In the study, a group of students whose members held opposing viewpoints on the topic of capital punishment were asked to evaluate two fictitious studies.

One study provided data in support of the argument that capital punishment deters crime, while the other supported the opposite viewpoint – that capital punishment had no appreciable effect on overall criminality in the population.

Both studies were entirely made up: They were designed to present “equally compelling” objective statistics, not to report on observed facts. The researchers discovered that responses to the studies broke down by participants’ existing opinions:

  • The participants who initially supported the pro-deterrence argument considered the anti-deterrence data unconvincing and rated data in support of their position to be credible;
  • Participants who had an anti-capital punishment stance at the beginning of the study reported the reverse opinion.

What’s more, at the end of the study, both groups reported that they felt more strongly about their original beliefs rather than less. The net effect of having their position challenged was an intellectual retrenchment of their existing belief system.

Examples of confirmation bias can also be detected spontaneously in day-to-day situations.

A detailed analysis of social media habits by both ordinary voters and political candidates shows that, broadly speaking, both more liberal and more conservative users have specific media sources they are more likely to seek out and share with others.

The challenging cognitive tendency toward confirmation bias can be amplified by technology in other ways. A phenomenon known as the filter bubble effect means that, as you use particular websites and content networks, those networks are more likely to serve you content you prefer while excluding content that your browsing patterns have demonstrated you do not prefer.

Over time, this may cause information contrary to your existing opinions to be completely excluded from your online experience – meaning you would have to expend even more time and effort actively seeking out evidence that conflicts with your assumptions.

More information

Confirmation bias is considered to affect both individuals and organizations. Analyst Mark Monroe, author of “Perception is Deception: A Brief Look at Confirmation Bias,” states that “confirmation bias occurs from the direct influence of desire on beliefs.”

Naturally, desires can be expressed individually or in a group context. Desires can also combine in complex, counterproductive ways in groups, particularly when status or money are at stake.

For example, individuals may be biased toward a certain hypothesis and wish to maintain the approval of a supervisor or peer group. The combination of confirmation bias with these other social pressures can give rise to – and sustain – a culture of groupthink.

In such a situation, confirmation bias can significantly worsen an organization’s challenges by contributing to the assumption that harmony and group coherence are the values most crucial to success. This reduces the likelihood of outright disagreement and the reassessments it can spark.