Twenty-five years ago, two American psychologists identified a puzzling phenomenon: the less people know and understand, the more they overestimate their knowledge. Today, this cognitive bias is known as the Dunning-Kruger effect.
In 1995, a robber stormed into two banks in Pittsburgh, Pennsylvania. Typically, robbers wear ski masks or other disguises to make it harder for the police to identify them afterwards. But this particular robber believed he had a more ingenious solution. Instead of using a cumbersome mask, he smeared lemon juice on his face, convinced it would make him invisible to security cameras. His reasoning? Lemon juice is used as invisible ink, so it must also render a person invisible to surveillance.
Unsurprisingly, his creative plan failed, and he was swiftly arrested. But the story didn’t end there. When psychologists Justin Kruger and David Dunning from Cornell University learned about the case, they recognized a deeper psychological phenomenon at play. The robber’s ignorance prevented him from realizing just how misguided his thinking was. In other words, he was too ignorant to recognize his own ignorance.
This insight led Kruger and Dunning to study the gap between people’s self-perception of their own abilities and their actual abilities. In 1999, they published their findings in the Journal of Personality and Social Psychology. Their conclusion was that people who lack skill in a particular area face a double disadvantage: not only does their incompetence lead them to make poor decisions, but they also lack the awareness to recognize their own shortcomings—meaning they don’t seek to improve. Over time, this phenomenon became known as the Dunning-Kruger effect.
Too ignorant to recognize his own ignorance. A diagram illustrating the relationship between confidence—how much we think we know—and actual knowledge. | Shutterstock, VectorMine
When We Don’t Know What We Don’t Know
The Dunning-Kruger effect is a cognitive bias in which individuals with limited knowledge or skills in a particular field tend to overestimate their own competence. Researchers attribute this bias to the fact that recognizing one's own ignorance requires at least a basic level of understanding—something those affected by the effect lack. Because they are unaware of their own shortcomings, they tend to believe they know and understand more than they actually do.
In a series of four experiments, Dunning and Kruger assessed the performance of several dozen students on tests measuring humor, logical reasoning, and grammar. Participants were also asked to evaluate their own abilities in these areas. The results showed a clear pattern: those who performed poorly consistently overestimated their abilities, while high performers tended to underestimate themselves. The researchers proposed that unskilled individuals fail to recognize their incompetence because they lack the cognitive ability to assess their own skills accurately.
In 2002, other researchers published a paper challenging Dunning and Kruger’s explanation of the effect, arguing that it does not stem from differences in cognitive ability but rather from the interplay of two other factors. The first is a statistical phenomenon known as ‘regression to the mean’, a statistical phenomenon that predicts individuals who score particularly low on a test will tend to overestimate their abilities, while those who score particularly high will underestimate them—bringing both groups' self-assessments closer to the average. This pattern is similar to how, in a given population, sons tend to be closer in height to the average than their fathers: extremely short fathers often have taller sons, while very tall fathers tend to have shorter sons.
The second factor is another cognitive bias known as the ‘above-average effect’, in which people tend to overestimate their abilities and believe they are better than average in various domains. The researchers argued that a combination of regression to the mean and the above-average effect is sufficient to explain the Dunning-Kruger effect, without requiring an additional cognitive explanation.
Since then, numerous studies have explored whether the Dunning-Kruger effect applies across different fields. A 2016 systematic review analyzed findings from 53 studies that examined the effect in the context of information literacy - the ability to identify, locate, evaluate, organize, and effectively use and communicate information. The studies included in the review compared individuals' self-assessments of their information literacy skills with their actual abilities in the field. In most cases, those with lower performance significantly overestimated their competence.
In most cases, people with lower performance significantly overestimated their abilities. Illustration of overconfidence. | Shutterstock, ArtemisDiana
Dunning-Kruger in Practice
One area where the Dunning-Kruger effect may have significant consequences is politics. Researchers suggest that individuals with limited knowledge about current public issues tend to overestimate their expertise, leading them to express strong political opinions while rejecting opposing arguments.
Overconfidence in political knowledge also influences how people assess the expertise of others. In a 2018 study, more than 2,500 participants completed online surveys testing their political knowledge and asking them to self-assess their expertise. The results revealed a clear pattern: participants with lower political knowledge scores significantly overestimated their competence—both in absolute terms and relative to others.
A more recent study examined whether the rise of social and digital media in recent years has intensified the Dunning-Kruger effect. The researchers argued that over the past 15 years, the expansion of the internet and online information sources has fundamentally transformed the media landscape, increasing public exposure to political discussions. They hypothesized that consuming political news through social media could amplify the effect by fostering a false sense of expertise. Indeed, a comparison of surveys conducted in 2008 and 2020 found that the effect had intensified over those years. However, the researchers noted that it remains unclear whether the online environment itself fuels overconfidence or whether individuals who already overestimate their political knowledge are simply more likely to consume online news content.
The Dunning-Kruger effect can have negative consequences across various domains, but its impact is particularly pronounced in sensitive areas like politics. When individuals with limited knowledge in a complex and important field perceive themselves as experts, they are more likely to adopt rigid and extreme positions while dismissing arguments that challenge their beliefs. This dynamic makes meaningful, rational discussions on critical issues increasingly difficult. Recognizing the effect and understanding its influence are essential for acknowledging the limits of our knowledge—especially in areas that directly affect society and daily life.