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The Dunning-Kruger effect also referred to as “Mount Stupid”, is a common and widely-known cognitive bias. It is named after the two researchers, David Dunning and Justin Kruger, who identified it in 1999.

🧠 In short: It describes the tendency of low performers to see themselves as more knowledgeable and capable than they really are. This happens because low-competence individuals tend to be unable to determine the true level of their own abilities, as well as recognize the skills of others.

Dunning-Kruger Effect

What Is the Dunning-Kruger Effect?

The Dunning-Kruger effect is a bias whereby people with low ability in a certain area tend to overestimate their capability in that area.

Most of us can likely think of a situation where someone’s behavior was (likely) influenced by it. For example, it’s not uncommon to hear people make overconfident claims and give lengthy speeches about something that they, in reality, know much less about than they let others understand. Thus, people falling prey to this effect are also described to be on “Mount Stupid”.


The main reason behind it is that low-skilled people lack the needed self-awareness to properly assess their performance. As Dunning and Kruger explained¹:

Overestimation occurs, in part, because people who are unskilled in these domains suffer a dual burden: Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it.

David Dunning and Justin Kruger (1999), “Unskilled and Unaware of It: How Difficulties in Recognizing One’s Own Incompetence Lead to Inflated Self-Assessments

In other words, being unable to judge the level of own performance, and thus the performances of other people leads to an inaccurate sense of one’s capabilities.


The concept is named after David Dunning and Justin Kruger of Cornell University, who identified the phenomenon as a cognitive bias in their 1999 paper.

In their studies, they tested the subjects in three areas: grammar, logic, and sense of humor. The results showed that those individuals who got the lowest scores in the tests consistently rated their own performances higher than what the scores revealed. More precisely, people whose scores placed them in the 12th percentile ranked themselves, on average, in the 62nd percentile.

Impostor Syndrome

A psychological phenomenon known as “impostor syndrome” is the opposite of the Dunning-Kruger effect. It refers to the belief that one is not as competent as their achievements show and/or other people perceive them to be.

It involves the idea that one has succeeded previously due to chance and luck, not because they are skilled or talented, and that someone will eventually find out — hence the name “impostor syndrome”.