The quote above comes from the philosopher Bertrand Russell. Psychological research has now shown he was right.
The Dunning-Kruger effect is the finding that the poorest performers are the least aware of their own incompetence. The effect has been:
"...replicated among undergraduates completing a classroom exam (Dunning, Johnson, Ehrlinger, & Kruger, 2003), medical students assessing their interviewing skills (Hodges, Regehr, & Martin, 2001) clerks evaluating their performance (Edwards, Kellner, Sistrom, & Magyari, 2003), and medical lab technicians evaluating their on-the-job expertise (Haun, Zeringue, Leach, & Foley, 2000)." (From Ehrlinger et al., 2008)
The reason seems to be that poor performers fail to learn from their mistakes.
The proposed solution is that the incompetent should be directly told they are incompetent.
Unfortunately the problem is that incompetent people have probably been getting this type of feedback for years and failed to take much notice. Despite failing exams, messing up at work and irritating other people, the incompetent still don't believe they're incompetent.
As Socrates once said:
"The only true wisdom is to know that you know nothing."
But even this can go too far. It turns out that people with real talent tend to underestimate just how good they are. The root of this bias is that clever people tend to assume other people find things as easy as they do, when actually this is their talent shining through (read on: The Worse-Than-Average Effect: When You’re Better Than You Think).
Image credit: Helga Weber
Cognitive Biases
→ This post is part of a series on cognitive biases:
- The Dunning-Kruger Effect: Why The Incompetent Don’t Know They’re Incompetent
- The Worse-Than-Average Effect: When You’re Better Than You Think
- Why You’re a Sucker for the Impact Bias
- The Hindsight Bias: I Knew It All Along!
- How to Overcome the Egocentric Bias
- See How Easily You Can Avoid The Memory Bias
- Why Your Future Self is an Emotional Mystery: The Projection Bias
- How To Avoid Choosing the Wrong Job or House: Fight the Distinction Bias
- 4 Belief Biases That Can Reduce Pleasure
- Does Delaying Decisions Lead to Better Outcomes?
- The Belief in a Just World: A Fundamental Delusion
- Why Society Doesn’t Change: The System Justification Bias
- The Availability Bias: Why People Buy Lottery Tickets
- The Illusion of Transparency
- The Illusion of Control: Are There Benefits to Being Self-Deluded?
- The Endowment Effect: Why It’s Easy to Overvalue Your Stuff
- Illusory Correlations: When The Mind Makes Connections That Don’t Exist

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