Has it ever seemed to you that less competent people rate their competence higher than it actually is, while more competent people humbly rate theirs lower?
It’s not just your imagination. This is a genuine cognitive bias called the Dunning-Kruger Effect.
The Dunning-Kruger experiments behind the research focused on cognitive tasks (logic, grammar, and evaluating humor), but similar disparities exist in other areas. In self-assessment of IQ, below average people overestimated their score and those above average underestimated (the Downing effect). Studies of healthy and unhealthy behaviors are handicapped when they rely on self-reporting because test subjects tend to improve their evaluation. In self-evaluations of driving ability, job performance, and even immunity to bias, we tend to polish our image.
This is the Lake Wobegone effect—the town where “all the children are above average.”
Notice that there are two different categories of error:
(1) the error where there is a preferred answer and everyone (apparently) is biased toward giving that answer (“How much snack food do you eat?” or “How popular would you say you are?” or “How good a driver are you?”) and
(2) the error where bias changes depending on actual competence, with the less and more competent groups rating themselves too high and too low, respectively.
Let’s look at the second category, where the two extremes make opposite errors. The results of the Dunning-Kruger research hypothesizes that the competent overestimate others’ skill levels. But the error is more complicated for the incompetent—they overestimate their own skill level and they lack the metacognition to realize their error. In other words, they were too incompetent to recognize their own incompetence. Improving their metacognitive skills drove down their self-assessment scores as they became better evaluators of their own limitations.
The original paper was titled, “Unskilled and Unaware of It,” for which the authors won an Ig Nobel Prize in 2000.

Ignorance more frequently begets confidence than does knowledge:
it is those who know little, not those who know much,
who so positively assert that this or that problem
will never be solved by science.
— Charles Darwin (The Descent of Man, 1871)

Photo credit: Martin Beek