As we first addressed in our posting Standing In Midair, cognitive bias is a limitation in our ability to think objectively. When you see a person materially overestimate their ability, the Dunning-Kruger Cognitive Bias is quite likely the cause. Somewhat surprisingly, this cognitive bias is also the likely cause when a person materially underestimates their ability. Social Psychologists, David Dunning, and Justin Kruger identified the illusion of superiority as a cognitive bias in their study “Unskilled and Unaware of It: How Difficulties in Recognizing One’s Own Incompetence Lead to Inflated Self-Assessments” (1999).
This first version of this bias results in a twofold effect. A person who is incompetent at something fails to see their incompetence. Then the person more often than not mistakenly believes they actually are competent, thus significantly overestimating their competence.