Confirmation Bias is when we act like a lawyer who looks for the particular evidence which will acquit a client he has already decided is innocent.
We like to believe we are rational creatures. We view ourselves as objective observers of reality, weighing evidence like a judge in a courtroom before arriving at a logical conclusion.
The truth, however, is that we are often more like a lawyer building a case for a client we have already decided is innocent.
This phenomenon is known as confirmation bias. It is a fundamental cognitive error that drives us to search for, favour, and recall information in a way that confirms our pre-existing beliefs or values.
Whether we are scrolling through our news feeds, debating politics at the dinner table, or investing in the stock market, confirmation bias is the invisible hand guiding us toward what we want to be true, while blinding us to what is true.
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Table of Contents
What Is Confirmation Bias?
Confirmation bias is a “mental shortcut” or heuristic that the brain uses to process the overwhelming amount of information we encounter daily. Rather than expending the massive cognitive energy required to critically evaluate every piece of new data, our brains prefer to fit new information into existing frameworks.
This bias manifests in three distinct ways:
- Biased Search: We actively seek out information that supports our views.
- Biased Interpretation: We interpret ambiguous evidence as supporting our existing attitudes.
- Biased Memory: We selectively remember information that reinforces our beliefs while forgetting contradictory details.
Psychologists have noted that this is not necessarily a malicious act of deception; it is often an automatic, unintentional strategy. However, the consequences can be profound, leading to overconfidence in personal beliefs and the maintenance of those beliefs even in the face of contradictory evidence.
This is also why persuasion techniques like the illusion of choice are so effective — once we already want to believe something, being offered a carefully framed “choice” simply gives us a satisfying way to confirm it.
Confirmation Bias Quotes
While modern psychology has given it a name of confirmation bias, the observation that humans are prone to this error is centuries old.
Confirmation Bias Studies
The Wason Test - The 2 4 6 Task
The term “confirmation bias” was coined in the 1960s by English psychologist Peter Wason.
In a famous experiment known as the “2-4-6 task,” Wason gave participants a sequence of numbers (2, 4, 6) and asked them to discover the rule behind it. They were allowed to test the rule by proposing their own three-number sequences.
Most participants hypothesized specific rules like “ascending even numbers” and tested sequences that confirmed that hypothesis (e.g., 8, 10, 12). They rarely attempted to falsify their hypothesis by testing a sequence that would violate it (e.g., 1, 2, 3). If they had, they would have discovered the actual rule was simply “any three numbers in ascending order”.
Wason demonstrated that people have a strong tendency to rely on a “positive test strategy”—seeking only evidence that confirms their theory while ignoring alternatives.
The Death Penalty Study
In 1979, researchers Lord, Ross, and Lepper conducted a landmark study involving participants who had strong feelings about capital punishment.
They presented subjects with two studies: one appearing to support the death penalty as a deterrent to crime, and one appearing to oppose it. Despite the evidence being balanced, participants on both sides felt their original views were strengthened.
They accepted the evidence that supported their view and aggressively criticized the methodology of the study that contradicted it.
This phenomenon, known as attitude polarization, shows how mixed evidence can actually drive people further apart.
How Confirmation Bias Works in Our Brain
Modern neuroscience suggests that confirmation bias is deeply rooted in our biology. High confidence in a decision acts as a top-down controller, modulating neural processing. When we are confident, our brains effectively “gate” information, amplifying the integration of confirmatory evidence while abolishing the processing of disconfirmatory evidence. This neural blindness to contradictory facts helps explain why the most confident people are often the hardest to persuade.
Confirmation Bias Examples in Real Life
Joe Public
Digital Echo Chamber
In the age of social media, confirmation bias has been weaponized by algorithms. Platforms utilize “algorithmic editing” and filter bubbles to display information users are likely to agree with, excluding opposing views.
This creates a feedback loop where our worldview is constantly reinforced. Because having our beliefs confirmed triggers a release of dopamine (a pleasure chemical), we are biologically incentivized to consume pundits and opinionators who echo our own thoughts
Financial Folly
In finance, confirmation bias can be disastrous. Investors often fall victim to the “disposition effect,” where they sell winning stocks too early and hold onto losing stocks too long.
An investor convinced that a specific company is a “winner” may ignore unfavourable news about that company or interpret market warnings as mere noise. They seek out forums and news sources that validate their investment thesis, leading to under-diversified portfolios and unnecessary risk
Gambler's Falacy
Gamblers often explain away their losses to maintain the belief that their chances of winning are higher than they really are.
By overweighting supportive evidence (a win) and underweighting opposing evidence (a loss), they maintain a belief in their own luck or skill
Scientists and Academics
The N-Ray Delusion
In 1903, French physicist René Blondlot announced the discovery of “N-rays,” a new form of radiation emitted by almost all substances. Dozens of other scientists published papers confirming the existence of N-rays, describing their ability to brighten electric sparks. The detection method relied on subjective visual observation in a dark room.
The phenomenon was debunked when American physicist Robert W. Wood visited Blondlot’s lab. During a demonstration, Wood secretly removed a crucial aluminum prism from the apparatus. Despite the machine being broken, Blondlot and his assistant continued to “see” the N-rays and report the data exactly as predicted. They were seeing what they expected to see, a classic case of bias overriding sensory reality.
Martian Canals
In the late 19th century, astronomer Percival Lowell popularized the idea that Mars was covered in artificial canals built by an intelligent civilization to irrigate their dying planet. Lowell produced intricate maps of these canals, and the public was captivated.
In reality, the canals were an optical illusion caused by looking through poor-quality telescopes at the limit of visibility. The eye tends to connect random point-like features into lines. Lowell was so convinced of his theory that he interpreted natural geological features and visual noise as engineering works. It wasn’t until the Mariner 4 flyby in 1965 that the idea was definitively debunked, revealing a barren, cratered world with no canals.
You can read more about the Martian Canals in our eBook A History of Aliens and Why We Believe
Cold Fusion
In 1989, electrochemists Martin Fleischmann and Stanley Pons announced they had achieved nuclear fusion at room temperature (“cold fusion”), producing excess heat that could not be explained by chemical reactions. While the media went into a frenzy, other scientists failed to replicate the results.
The controversy highlighted the “Experimenter’s Regress.” If a scientist believed in cold fusion, they interpreted null results as a failure of equipment. If they disbelieved, they interpreted positive results as measurement error. Proponents fell into a feedback loop, assuming their positive results were correct because they validated the theory, while ignoring the massive theoretical implausibility and lack of reproducibility
Conspiracy Theorists
David Icke
A prime example of this mechanism is found in the work of David Icke. The former TV sports presenter claims that the world is controlled by a secret group of shape-shifting reptilian aliens.
While this sounds outlandish to most, for those within the conspiracy community, it offers a “Grand Unified Theory” of suffering and a reason for evil.
To a believer, social ostracization—like being mocked for believing in lizard people—is not a sign that they are wrong, but rather confirmation that they are a brave truth-teller facing persecution
You can read about a very similar story in Will Camden’s novel Confessions of a Professional Conspiracy Theorist.
Flat Earth
Perhaps the most striking visual example of confirmation bias in action comes from the Flat Earth movement. In the documentary Behind the Curve, Flat Earthers devised an experiment using a ring laser gyroscope to prove the Earth is stationary.
Instead of proving their theory, the gyroscope detected a 15-degree-per-hour drift—exactly what would be expected on a rotating spherical Earth 40. Rather than accepting this disconfirming evidence, the believers immediately engaged in “mental gymnastics.” They dismissed the result, claiming the device was picking up the rotation of the “firmament” or “aether,” and sought ways to block the device from reading the Earth’s rotation to get the result they wanted 40.
In another experiment involving lasers across a lake, the results showed the water surface curving by several feet, obscuring the laser. Instead of accepting that the Earth is curved, the experimenters dismissed the result as “inconclusive” or due to equipment error 40. This perfectly illustrates the “positive test strategy”: they were not testing to see if the Earth was flat; they were testing to confirm it was flat. When the data said otherwise, the data was discarded.
The Satanic Panic
In the 1980s, America was gripped by a mass hysteria known as the Satanic Panic. Sparked by the book Michelle Remembers (which was later debunked), communities became convinced that daycare centers were fronts for massive Satanic cults abusing children 41.
Investigators and therapists, operating under extreme confirmation bias, used coercive interview techniques on children. They asked leading questions and refused to accept denials. If a child said nothing happened, it was interpreted as “repression” due to trauma. If a child agreed, it was “evidence” 42. In the McMartin Preschool trial, authorities dug up the grounds looking for secret tunnels. When they found none, it was interpreted not as innocence, but as proof of how sophisticated the cult’s cover-up was 43. Thousands of lives were ruined by a legal and media system that saw only what it wanted to see.
Why We're Not Stupid
Whenever a published fact, a new observation or thought came across me, which was opposed to my general results, to make a memorandum of it without fail and at once; for I had found by experience that such facts and thoughts were far more apt to escape from the memory than favourable ones".
Confirmation bias is not a sign of stupidity; it is a sign of humanity. It is the brain’s default mode of operation. However, we are not helpless against it.
To combat confirmation bias, we must adopt the tools of science. The most effective defence is the falsification strategy—actively trying to prove ourselves wrong rather than right. We must seek out diverse perspectives and establish objective decision-making systems, such as “blind” evaluations where we do not know the source of the data we are interpreting.
Perhaps the best advice comes from Charles Darwin. In his autobiography, he described a “golden rule” he followed to combat his own bias:
Many of these patterns show up repeatedly in conspiracy thinking and modern belief movements, and they’re explored in more depth in Confessions of a Professional Conspiracy Theorist.
By recognizing that we are the easiest people to fool, we take the first step toward seeing the world as it actually is, rather than how we wish it to be.
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