Confirmation Bias

Confirmation bias is the tendency to look for information that supports, rather than rejects, one’s preconceptions (American Psychological Association). People with this bias interpret evidence to confirm their existing beliefs while rejecting or ignoring anything that conflicts with them.

One of the earliest demonstrations of confirmation bias appeared in an experiment by Peter Wason (1960). Participants had to discover the experimenter’s rule for sequencing numbers.

Participants mostly tested hypotheses with triples that fit them. They rarely tried a triple that could prove them wrong. Only 6 of 29 named the correct rule without first announcing a wrong one (Wason, 1960).

Evidence of confirmation bias has appeared throughout psychological literature for a long time. The term itself is more recent: researchers first used ‘confirmation bias’ in a 1977 paper on scientific inference (Mynatt, Doherty, & Tweney, 1977).

Types of Confirmation Bias

Examples of Confirmation Bias

Social Media

Information on social media reflects both what users want to see and the platform designers’ own beliefs and values. Today, people face an overwhelming number of news sources, each varying in credibility.

People tend to read news that suits their views. News channels often cover the same issue differently, and some rely on sensational headlines and one-sided information. Racism and party politics are two examples.

Due to the biased coverage of topics, people only utilize certain channels/sites to obtain their information to make biased conclusions.

Religious Faith

People also tend to search for and interpret evidence with respect to their religious beliefs (if any).

On topics such as abortion and transgender rights, people whose religion opposes them interpret information differently from others. They look for evidence that validates what they already believe.

Similarly, those who religiously reject the theory of evolution will either gather information disproving evolution or hold no official stance on the topic.

Irreligious people may see the same events differently. What religious people call “miracles” or “tests of faith,” they may read as reinforcement of their own lack of belief.

Science, Medicine, Law and Finance

Confirmation bias also distorts high-stakes professional judgments. In every field below, an early belief steers which evidence is collected and how it is read.

The remedy is the same each time: treat the early belief as a hypothesis to test, not a conclusion to defend. The four examples below show how this plays out in practice, in science, medicine, law and finance.

Science

The bias is the psychological opposite of good scientific method. Popper (1959) argued that confirming instances can never prove a hypothesis, but a single counter-instance can disprove it.

Science should therefore proceed by bold conjecture and rigorous attempts at falsification. Controlled experiments, blinding, pre-registration and independent replication exist to force the disconfirming tests that individual reasoners avoid.

Medicine

A clinician who fixes on an early diagnosis may order tests that confirm it. Ambiguous findings get read as consistent with it. Data pointing elsewhere are discounted.

This links to premature closure and anchoring on a first impression. The antidote is to treat the working diagnosis as a hypothesis. Ask what else could explain the symptoms. Cognitive behavioral therapy trains patients to treat their own negative thoughts the same way.

Law

A detective who decides early that a suspect is guilty may attend mainly to incriminating evidence. Exonerating facts get overlooked or reinterpreted. This “forensic confirmation bias” can cause tunnel vision and wrongful conviction.

It can also contaminate forensic and eyewitness evidence. Knowing the expected answer can shape how an examiner reads an ambiguous fingerprint, or how a witness’s memory is reconstructed.

Finance

Investors tend to seek information confirming a prior conviction about a stock. They discount warning signs. This can sustain overconfidence in a failing position and lead to poorly timed decisions.

Why Confirmation Bias Occurs

Several explanations account for confirmation bias. It is an efficient way to process information, it protects self-esteem, and it minimizes cognitive dissonance, the discomfort of holding two conflicting beliefs (Festinger, 1957).

Information Processing

Confirmation bias serves as an efficient way to process information because of the limitless information humans are exposed to.

To form an unbiased decision, one would have to critically evaluate every piece of information present, which is unfeasible. Therefore, people only tend to look for information desired to form their conclusions (Casad, 2019).

One working hypothesis is cheaper to hold than several. Weighing evidence for competing hypotheses at once is demanding parallel processing, and the mind tends to avoid it.

Protect Self-esteem

People are susceptible to confirmation bias to protect their self-esteem (to know that their beliefs are accurate).

To make themselves feel confident, they tend to look for information that supports their existing beliefs (Casad, 2019).

This is a “hot” motivational route, not just a mental shortcut. Admitting that a cherished belief is wrong is uncomfortable.

Kunda (1990) called it motivated reasoning. When people want a particular conclusion, they search memory for beliefs and rules that would justify it. They must still build a justification that could persuade a neutral observer.

Disconfirmation bias fits this account. People work harder to rebut threatening evidence than supporting evidence (Taber & Lodge, 2006).

Minimize Cognitive Dissonance

Cognitive dissonance also explains why confirmation bias is adaptive.

Cognitive dissonance is a mental conflict that occurs when a person holds two contradictory beliefs and causes psychological stress or unease.

To minimize this dissonance, people adapt to confirmation bias by avoiding information that is contradictory to their views and seeking evidence confirming their beliefs.

Avoiding challenges and seeking reinforcement affect people’s thoughts and reactions differently. Disconfirming information triggers negative emotions, while reinforcing evidence does not (“The Confirmation Bias: Why People See What They Want to See”).

Dual-Process Theory and System 1

Psychologist Daniel Kahneman offers the most influential explanation for confirmation bias: dual-process theory. Two systems run the mind, he argues. A fast, automatic “System 1” handles most everyday thinking.

As Kahneman (2011) explains, System 1 builds the most coherent story it can from whatever information is active. He calls this tendency WYSIATI: “what you see is all there is.”

System 1 is primed to activate belief-consistent memories first. As Kahneman (2011) puts it, “the operations of associative memory contribute to a general confirmation bias.”

Doubting takes real effort. Kahneman (2011) puts it starkly: “System 1 is gullible and biased to believe, System 2 is in charge of doubting and unbelieving.” System 2, he adds, is often too busy or too lazy to check.

Even deliberate thought inherits the bias. As Kahneman (2011) explains, “a deliberate search for confirming evidence, known as positive test strategy, is also how System 2 tests a hypothesis.”

“Contrary to the rules of philosophers of science, who advise testing hypotheses by trying to refute them, people (and scientists, quite often) seek data that are likely to be compatible with the beliefs they currently hold.” (Kahneman, 2011)

On this account, confirmation bias is the default output of an efficient associative system that a lazy monitor rarely checks.

Implications of Confirmation Bias

Confirmation bias consistently shapes the way we look for and interpret information that influences our decisions in this society, ranging from homes to global platforms. This bias prevents people from gathering information objectively.

Politics

During the election campaign, people tend to look for information confirming their perspectives on different candidates while ignoring any information contradictory to their views.

This one-sided way of gathering information can breed overconfidence in a candidate. It can also cause voters to misread or overlook important facts, ultimately swaying their vote and the country’s leadership (Cherry, 2020).

Digital platforms intensify the pattern. Recommendation algorithms feed users more of the content they already engage with.

The result is echo chambers and filter bubbles, where people mostly meet views like their own. Disconfirming views are rarely seen, beliefs harden, and communities drift further apart.

Recruitment and Selection

Confirmation bias also affects employment diversity. Preconceived ideas about different social groups can introduce unconscious discrimination into the recruitment process (Agarwal, 2018).

A belief that one group is more competent than another helps explain why certain races and genders are over-represented in companies today. This bias can undermine a company’s efforts to diversify its workforce.

The bias works through the interview itself. A preconception about a candidate can shape which questions an interviewer asks and how the answers are read.

The same applies beyond hiring. Once we form a view of a person, we notice behaviour that fits it and explain away behaviour that does not.

Mitigating Confirmation Bias

Question Your Sources and Habits

To avoid being susceptible to confirmation bias, start questioning your research methods, and sources used to obtain their information.

Expanding the types of sources used in searching for information could provide different aspects of a particular topic and offer levels of credibility.

• Read Fully: Read entire articles rather than forming conclusions from headlines and pictures.
• Verify Evidence: Search for credible evidence presented in the article itself.
• Check Sources: Track the source of a claim to judge how trustworthy it is.
• Stay Conscious: Encourage yourself and others to gather information deliberately, not passively.

Consider Alternative Hypotheses

Confirmation bias occurs when people look for information that confirms their beliefs or hypotheses. Considering alternative hypotheses and their consequences can help reduce it.

Considering the possibility of beliefs/hypotheses other than one’s own could help you gather information in a more dynamic manner (rather than a one-sided way).

The best-supported technique is to ask, “Why might my judgment be wrong?” Lord, Lepper, and Preston (1984) found that instructing people to consider the opposite reduced biased assimilation. Simply urging them to be unbiased did not.

You can also test a belief by looking for evidence that could refute it, and give real weight to sources that disagree with you.

Critical Evaluation

Confirmation bias is one of psychology’s most heavily replicated effects, but recent scholarship has qualified how it should be interpreted. Before looking at each qualification, here is a short summary:

1. Positive Testing Is Often Rational: the classic reasoning tasks may conflate seeking confirmation with a testing strategy that is usually sensible.
2. Card Choices May Be Rational: an information-gain model explains the usual selection-task choices without invoking a bias.
3. Mild Bias Can Be Adaptive: committing to a working hypothesis brings useful cognitive stability, not just error.
4. The Mechanism Is Contested: researchers still debate how much of the bias is cold processing versus hot motivation, and how far lab tasks generalize.

Positive Testing Is Often Rational

Klayman and Ha (1987) argued that Wason’s 2-4-6 task conflates two different things. Seeking confirmation is a goal. Using a positive-test strategy, checking cases you expect to be positive, is just a method.

In most real environments, a hypothesised category is narrower than the true category. Testing positive cases is then an efficient way to expose errors. That is the key insight.

Wason’s task is unusual because the true rule, “any ascending triple,” is maximally general. Positive tests of a narrower hypothesis can never disconfirm a rule that broad.

Under ordinary conditions, the same positive-test strategy would quickly reveal a wrong rule. Not Wason’s task, though. What the classic tasks expose may be less a flaw in human reasoning. It looks more like a mismatch between an adaptive heuristic and an artificially rigged task.

That reframing matters.

Rational Analysis of the Selection Task

Oaksford and Chater (1994) offered the strongest rival to a confirmation-bias reading of Wason’s selection task. Their idea was simple. They modeled it as an optimal data-selection problem rather than a processing defect.

Suppose a reasoner assumes that the property named in the rule, such as being a vowel, is rare among possible cards. Under standard Bayesian assumptions, the cards with the most expected information gain closely match the A and 4 cards.

The usual choices then look rational. They can emerge from an information-maximizing strategy applied to plausible real-world assumptions.

This is a genuine rival account, not a mere qualification. The two accounts disagree on whether the classic selection-task data need a bias explanation at all.

Adaptive and Ecological Accounts

Some theorists treat a mild bias toward a current best hypothesis as adaptive. Committing provisionally to a working model provides useful cognitive stability.

It also avoids the paralysis of constantly re-litigating settled beliefs. Verifying instances is usually cheaper to obtain than decisive falsifiers, so seeking confirmation can be a reasonable default.

Nickerson’s (1998) landmark review took a balanced position. It is genuinely widespread and consequential, he concluded. But positive-test behaviour is not always the error it is sometimes portrayed as.

This reading does not deny that confirmation bias is real. It simply argues that a mild pull toward one’s working hypothesis served people well historically. Confirming evidence was often the only evidence readily available. That is a genuine strength, not just a flaw.

Cognitive vs Motivational Debate

Researchers still debate the cause. Is it a “cold” cognitive limitation, a by-product of associative processing? Or a “hot” motivational defence of self-esteem and worldview? The evidence indicates both contribute, weighted by how personally invested a reasoner is.

Kahneman (2011) locates the cause in memory and attention. Kunda’s (1990) motivated-reasoning account argues that part of the effect is goal-directed instead. Reasoners unconsciously build a case for a desired conclusion to protect self-esteem or identity.

These are rival explanations for overlapping data. As Nickerson (1998) noted, the field has not settled which does more of the work, so most accounts treat them as complementary.

A further caution concerns the tasks themselves. Many demonstrations rely on artificial, single-shot laboratory problems, and the effect can shrink once reasoners get feedback and real-world experience.

Neither account alone tells the full story. A complete picture of confirmation bias needs both the cognitive shortcut and the motivational defence, weighted differently from person to person and topic to topic. Real-world judgement, backed by feedback and experience, may end up less biased than a single laboratory task suggests.

That is the honest, unresolved state of the debate.

Contemporary Research

A striking finding from this period concerns motivated numeracy: people with more numerical skill use it to defend their political identity.

This overturns a common assumption: that biased reasoning is simply a skills deficit more education would fix. On divisive, identity-relevant questions, cognitive sophistication can serve confirmation rather than counter it (Kahan et al., 2017).

Related Cognitive Biases

Confirmation bias sits at the centre of a cluster of belief-preservation effects, and many other cognitive biases overlap with it. Four of the closest are covered below.

Backfire Effect

The backfire effect occurs when contradictory evidence strengthens a person’s preexisting beliefs (Nyhan & Reifler, 2010). Disproving a misconception can therefore entrench it.

One piece of disconfirming evidence does not change people’s views, but a constant flow of credible refutations could correct misinformation/misconceptions.

Backfire relates to confirmation bias. It describes how people react to new information through their preexisting hypotheses.

More recent, larger studies suggest the backfire effect is rarer and less robust than early research implied. Most people do update their views toward a correction, at least somewhat. Backfire is possible. It is not the routine outcome.

For example:

A study by Brendan Nyhan and Jason Reifler (two researchers on political misinformation) explored the effects of different types of statements on people’s beliefs.

They compared two statements: “I am not a Muslim, Obama says” and “I am a Christian, Obama says.” The second, affirming statement proved more persuasive and changed more people’s beliefs, suggesting affirming statements correct incorrect views more effectively than simple denials (Silverman, 2011).

Halo Effect

The halo effect occurs when people use impressions from a single trait to form conclusions about other unrelated attributes. It is heavily influenced by the first impression.

American psychologist Edward Thorndike pioneered research on this effect. In 1920, he described how officers rated soldiers on different traits based on first impressions alone (Thorndike, 1920).

Experiments have shown that when positive attributes are presented first, a person is judged more favorably than when negative traits are shown first. It relates to confirmation bias because it lets us structure our thinking about other information using only initial evidence.

Belief Perseverance

Belief perseverance is the tendency to cling to a belief even after the evidence that first supported it has been discredited. It sits alongside confirmation bias in a wider cluster of belief-preservation effects.

Confirmation bias helps keep a perseverant belief alive. Biased memory keeps supporting details easy to recall, while biased interpretation keeps explaining away each new piece of disconfirming evidence.

Psychologists see this as a natural extension of the same search, interpretation and memory biases already explained in this article. A belief rarely falls apart just because its original evidence quietly disappears.

This has practical consequences. A jury that formed an early impression of a defendant’s guilt, for instance, may keep discounting later evidence that points the other way.

That persistence is the whole point.

Myside Bias

Myside bias is a closely related term from the reasoning literature. It describes evaluating evidence, generating arguments, and testing hypotheses in ways that favour one’s own prior opinions.

Some researchers use myside bias as a near-synonym for the motivated, self-protective side of confirmation bias.

The two terms overlap heavily in practice. Where confirmation bias covers search, interpretation and memory together, myside bias puts the spotlight on argument and hypothesis generation specifically.

Either way, the underlying pull is the same. People build a case for what they already believe, rather than testing it fairly against the alternatives.

This matters because myside reasoning can look rigorous. A person marshals real evidence and logical-sounding arguments; the bias lies in which side they chose to defend.

Learning Check

When does the confirmation bias occur?

1. When an individual only researches information that is consistent with personal beliefs.
2. When an individual only makes a decision after all perspectives have been evaluated.
3. When an individual becomes more confident in one’s judgments after researching alternative perspectives.
4. When an individual believes that the odds of an event occurring increase if the event hasn’t occurred recently.

The correct answer is A. Confirmation bias occurs when an individual only researches information consistent with personal beliefs. This bias leads people to favor information that confirms their preconceptions or hypotheses, regardless of whether the information is true.

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