Courtesy of TM (Trademark of Intel):
The Dunning–Kruger effect is acognitive bias in which unskilled people make poor decisions and reach erroneous conclusions, but their incompetence denies them themetacognitive ability to recognize their mistakes. The unskilled therefore suffer from illusory superiority, rating their ability as above average, much higher than it actually is, while the highly skilled underrate their own abilities, suffering from illusory inferiority.
Actual competence may weaken self-confidence, as competent individuals may falsely assume that others have an equivalent understanding. As Kruger and Dunning conclude, "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". The effect is about paradoxical defects in cognitive ability, both in oneself and as one compares oneself to others.
Although the Dunning–Kruger effect was put forward in 1999, David Dunning and Justin Kruger have quoted Charles Darwin ("Ignorance more frequently begets confidence than does knowledge") and Bertrand Russell ("One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision") as authors who have recognised the phenomenon.
The hypothesized phenomenon was tested in a series of experiments performed by Justin Kruger and David Dunning, both then of Cornell University. Kruger and Dunning noted earlier studies suggesting that ignorance of standards of performance is behind a great deal of incompetence. This pattern was seen in studies of skills as diverse as reading comprehension, operating a motor vehicle, and playing chess or tennis.
Kruger and Dunning proposed that, for a given skill, incompetent people will:
tend to overestimate their own level of skill;
fail to recognize genuine skill in others;
fail to recognize the extremity of their inadequacy;
recognize and acknowledge their own previous lack of skill, if they can be trained to substantially improve.
Dunning has since drawn an analogy ("the anosognosia of everyday life") to a condition in which a person who suffers a physical disability because of brain injury seems unaware of or denies the existence of the disability, even for dramatic impairments such as blindness or paralysis.