The Dunning–Kruger effect

In 1995 a man robbed two banks in Pittsburg, America in the middle of the day. He didn’t wear a mask, seemingly there was no effort on his side to hide his identity. The man simply entered into the banks with a gun and demanded that the money be handed to him. That man was called McArthur Wheeler.

Without much trouble the police caught him the same night after looking at the surveillance cameras footage. They showed Mr. Wheeler the tapes. He stared with disbelief – “But I wore the juice!” he mumbled with amazement. Apparently, McArthur Wheeler believed that rubbing lemon juice on one’s face would render it invisible, since lemon juice was used as “invisible” ink.


Success and satisfaction depend on our knowledge, understanding, wisdom and ultimately the ability to make decisions based on the information we have and our assessment of the situation. We can apply different strategies based on that assessment and that brings us to either a better or worse situation.

The problem comes exactly when we try to assess the situation and our abilities to deal (or not) with it.

Dunning and Kruger

In 1999 David Dunning and Justin Kruger did a series of experiments while in the department of psychology at Cornell University. Their study was inspire precisely by the case of Mr McArthur Wheeler.

What the two discovered was that:

ignorance of standards of performance lies behind a great deal of incorrect self-assessment of competence

or in other words, when we think something is easy to do it is because we cannot estimate how good we are at doing it.

Dunning and Kruger attributed this bias to a metacognitive inability of the unskilled to recognize their own ineptitude and evaluate their own ability accurately.

The paradox

What Dunning and Kruger discovered was a cognitive bias, or for me a paradox. The psychologists found that people who were less skilled believed they are in fact much better than their skill level. And people who were very good at what they do believed that they were average or less.

“The miscalibration of the incompetent stems from an error about the self, whereas the miscalibration of the highly competent stems from an error about others.”

In other words, people who are not good at doing something, have no understanding of what good actually means because they do not spend a lot of time in that domain. Because of that, they see the little achievements as huge successes and overestimate the quality of what they have accomplished. The incompetent have a wrong understanding about themselves, they will:

  • fail to recognize their own lack of skill
  • fail to recognize the extent of their inadequacy
  • fail to recognize genuine skill in others
  • recognize and acknowledge their own lack of skill, after they are exposed to training for that skill

On the other hand, people who are very good or experts in a certain field have an extremely tuned, detailed understanding of what the best possible outcome of what they do is. Because of that they judge their own efforts with this extreme standard for quality and see their own accomplishments as unsatisfactory or mediocre. The experts have the wrong understanding about others, because they think that what they can do would be as easy for everyone else and that they won’t be good enough until what they can do is unachievable by anyone else but them.


Each of us is on the spectrum between unskilled to highly skilled in different domains in life. We would always fail to estimate our skills accurately to some degree. It’s human, it’s ok. But it is important to be aware of this bias. Most people around me suffer from the latter case, where they undervalue their skills and accomplishment simply because they evaluate them against an extremely high standard. Chill (I’m telling this to myself right now as well)! Look around, how many people can do what you do with ease? How long did it take you to get there? There is a lot of time, energy, consistency and effort involved, give yourself some credit!


The burglar with the lemon juice disguise

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