The Dunning-Kruger effect: what the study really says and how it is misunderstood

The experiments by David Dunning and Justin Kruger (1999), the statistical critiques and a useful lesson for all of us

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Translated from the Albanian original by the editors. Shqip

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Illustration: a lamp, a symbol of the light that shows how little we know
Original illustration by the lexoshpejt editors. Not a historical photograph or object.
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You may have seen on social media a graph with a high hill called "Mount Stupid" and a valley called "the valley of despair". It is often presented as "the Dunning-Kruger effect". But the original study contains no such graph.

The 1999 study

The psychologists Justin Kruger and David Dunning at Cornell University gave students tests on humour, logical reasoning and grammar. After each test they asked them how they thought they had ranked compared with the others.

Students with the weakest results, in the bottom quarter, thought on average that they had done better than about 60 per cent of the others, while in fact they had done worse than about 88 per cent. Students with the best results, by contrast, slightly underestimated their ranking. The explanation proposed by the authors: to recognise that you are not good at something, you need precisely the skills you lack.

The critiques

In the years that followed, some researchers argued that part of the effect can be explained by statistics. When people find it hard to assess themselves accurately, their estimates tend towards the middle. This makes the weak look overconfident and the strong look underconfident, even without any special "blindness". The debate continues. Many researchers accept that people with lower skills are on average less accurate in self-assessment, but the effect seems smaller and more complicated than popular culture presents it.

The real lesson of Dunning-Kruger is not "others don't know that they don't know". It is "I don't always know how much I know, either".

How it is misunderstood

  • It does not mean that inexperienced people are more confident than experts. In the study, experts were confident too; they simply had more reason to be.
  • It is not a label for other people. It is often used to mock others, while it applies to all of us, in the fields where we are not experts.
  • The "Mount Stupid" graph does not come from the study. It is a popular illustration.

How to check your self-assessment

  1. Ask for concrete feedback from someone who knows the field well.
  2. Test yourself with real questions or tasks, not only with the feeling that you know.
  3. Learn the basics of a field before giving strong opinions on it.
  4. Express confidence in measure: "I think that", "I am not sure, but".

Sources and further reading

  1. Kruger, J. & Dunning, D. (1999). Unskilled and unaware of it: How difficulties in recognizing one’s own incompetence lead to inflated self-assessments. Journal of Personality and Social Psychology, 77(6), 1121–1134. doi:10.1037/0022-3514.77.6.1121
  2. Dunning, D. (2011). The Dunning–Kruger effect: On being ignorant of one’s own ignorance. Advances in Experimental Social Psychology, 44, 247–296. doi:10.1016/B978-0-12-385522-0.00005-6

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