The Dunning-Kruger effect describes a pattern in which people with low skill in an area tend to overestimate their performance, partly because judging performance draws on the very skill in question.¹
Where it comes from
David Dunning and Justin Kruger, then at Cornell, were intrigued by a 1995 Pittsburgh bank robber who had rubbed lemon juice on his face, convinced it would hide him from security cameras. In four studies on humor, logical reasoning and grammar, participants who scored in the bottom quarter placed themselves, on average, above the middle of the pack. The top scorers, interestingly, tended to underestimate their standing.¹
Where it goes wrong
The popular chart with "Mount Stupid" and a "Valley of Despair" comes from internet memes; it appears nowhere in the paper. The term is also used to call other people incompetent. Researchers have debated how much of the pattern reflects statistical artifacts such as regression to the mean.² Dunning's own summary stresses that the effect concerns all of us, in whatever areas we lack expertise.³
Talent Takeaway
Before a big decision in unfamiliar territory, rate your plan yourself, then ask someone with expertise to rate it too. The gap between the two ratings is valuable information. In teams, frequent and specific feedback closes blind spots quickly.
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. https://doi.org/10.1037/0022-3514.77.6.1121
² Gignac, G. E., & Zajenkowski, M. (2020). The Dunning-Kruger effect is (mostly) a statistical artefact: Valid approaches to testing the hypothesis with individual differences data. Intelligence, 80, 101449.
³ Dunning, D. (2011). The Dunning–Kruger effect: On being ignorant of one's own ignorance. Advances in Experimental Social Psychology, 44, 247–296.
Further reading: Grant, A. (2021). Think again: The power of knowing what you don't know. Viking.