Bias: The Dunning-Kruger effect

In order to act Customer Experience Manager Evidence Based, it is important to recognize (own) qualities and pitfalls. Psychologists like the well-known Tversky and Kahneman have delved into what drives human action and how our own brains can fool us. As a scientist, doctor, researcher or Evidence Based Professional It is of great importance to be aware of such thoughts patterns and pitfalls. Within PEBex, we spend next to research blemish methodology, red flags, resistances, and insight in CEM also attention to the psychological insights that can explain the actions of ourselves and others. In every newsletter we discuss a Bias, which sends us thinking in a certain direction. We start with the Dunning – Kruger effect. Darwin wrote in 1871 al:

“Ignorance more frequently gets confidence than does knowledge” and Thomas Jefferson said, “He who knows best, best knows how little He knows”

In 1999, this self-overestimation was given a name: the Dunning-Kruger effect. The Dunning – Kruger effect is a bias in which people with average skills in a particular field believe that they perform superiorly. People with limited skills in a certain area, lack the ability to see that they draw the wrong conclusions and make decisions (meta-cognitive ability). In short, people often seem to overestimate themselves, especially when they perform badly. We all know someone, and when we are honest, we sometimes see that person in the mirror, who, after making an error, remains convinced of his own competent actions. But the reverse also proved true. Russell formulated this as follows: “In the modern world the Blockheadss walk over from self-assurance while they are with intelligence a and all doubt.” So where people with average skills in a particular field believe that they perform superiorly, people with above skills underestimate their own performance. People who have above-average skills and perform well, assume that what is easy for them is easy for others too (the false consensus effect). Four studies of Dunning and Kruger showed that virtually everyone overestimated his or her own qualities. The 25% worst performing people, thought they scored in the top 10. The only exception to this is the actual performance of the performers, they underestimate themselves correctly. It also looked at the extent to which, in addition to assessing its own qualities, it was able to assess the performance of others. Participants who performed poorly in a domain were also less able to accurately assess the qualities of others. While the Excelrs in a domain were able to correctly assess the skills of others. In short, incompetent persons were less able to estimate competence among others. Another interesting effect was visible; As soon as the Excelrs faced the results of others (less performing) participants, they became more confident about their own ability. They saw that the task for others was not as easy as they had previously thought.

According to Dunning and Kruger, someone with limited skills for a particular activity will:

  • Significantly overestimates the own actions and their own results.
  • Not recognise to what extent he or she is incapable.
  • Not be able to recognize or judge this skill in others.
  • Recognize the own lack of qualities after a training for the required skill.

Thus, the Dunning-Kruger effect occurs especially when you take on a task for which you do not have the necessary knowledge and if there is no one to keep a mirror for. In short: Learning with others and getting feedback helps! That’s why we also work with Peer groups within PEBex. Working with and observing the behaviour and skills of others ensures that we are better able to assess our own skills.


  1. Kruger, Justin, David Dunning (1999). Unskilled and unaware of It: How Difficulties in recognizing one’s ‘s Own incompetence Lead to inflationary Self-assessments. Journal of Personality and Social Psychology 77 (6): 1121 – 34. PMID: 10626367. DOI: 10.1037/0022-3514.77.6.1121.
  2. Bertrand Russell, The Triumph of Stupidity (1933-05-10) in Mortals and others: Bertrand Russell’s American essays, 1931-1935 (Routledge, 1998, ISBN 0-415-17866-5), p. 28
  3. Ross, L., Greene, D., & House, P. (1977). The “false Consensus effect”: An egocentric bias in social perception and attribution processes. Journal of Experimental Social Psychology, 13, 279 – 301.
  4. The descent of Man, John Murray, London