The less we know about something, the worse we calibrate how much we know.
Someone who knows little about a topic often feels very confident giving an opinion on it, while a true expert tends to hesitate more, precisely because they know the complexity behind it. The Dunning-Kruger effect describes that inverse relationship between actual competence and perceived confidence.
In a study with college students, those who scored lowest on grammar, logic, and humor tests were, on average, the ones who most overestimated their own actual performance. Higher-performing students, by contrast, calibrated their self-assessment much more accurately, and even tended to slightly underestimate themselves.
The same skills needed to do something well are the ones needed to recognize that it's being done poorly. Someone who lacks those skills doesn't just fail, they also can't notice they're failing.
Source: Kruger, J. & Dunning, D. (1999). Unskilled and Unaware of It. Journal of Personality and Social Psychology, 77(6), 1121-1134.
In training and hiring, the confidence someone projects when talking about a topic isn't a good indicator of how much they actually know about it. Our own self-assessment case shows something similar. Giving concrete, quantitative feedback calibrates self-perception better than simply warning people about the bias.
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