The Dunning-Kruger effect is a cognitive bias where a low skilled, incompetent person is unable to see their own inability and as a result overestimates his or her competence. The converse, (though seen less) is also true, where a highly skilled person underestimates his own abilities, and overestimates the skill in others. Mastering a complex skill requires practice and self assessment over time. Since people suffering from the Dunning-Kruger effect are unable to see how bad their performance is, they are never able to self asses, move up the skills ladder, and thus never improve their abilities.
William Lidwell, Kritina Holden and Jill Butler, The Pocket Universal Principles of Design (USA: Rockport publishers, 2015), 40.
The Dunning Kruger effect can be applied to design by offsetting the effect by helping the user to understand how they are performing. For example by creating opportunities in a design that allow a person engaged in a task to see how well they did, showing how their performance compares to others, providing prompt relevant feedback, and by keeping future tasks locked until lower level tasks have been mastered. A design can exploit the effect in a negative way also. For example a system could make it difficult for the user to see how well they are performing, or deceives them into believing they are doing well in order to keep them engaged with a task.
Original source image
William Lidwell, Kritina Holden and Jill Butler, The Pocket Universal Principles of Design (USA: Rockport publishers, 2015), 40.
Online image
Zepp Golf 3D swing analyzer
https://www.apple.com/shop/product/HJZ52ZM/A/zepp-golf-2-3d-swing-analyzer?fnode=4a&fs=fh%3D35f7%252B3493
Real world image
Realtime leaderboard display at K1 Speed, Go kart racing track, Irvine