Have you ever noticed that the person with the least amount of knowledge on a subject is often the most confident to blast you with their opinion about it?
This is a well-known experience that can perhaps be explained by the Dunning-Kruger effect, a cognitive bias whereby people with limited ability in a given field tend to greatly overestimate their own competence. The less ability, the more they tend to overestimate their competence.
In a neatly animated video for TED-Ed, the Dunning–Kruger effect is explained by none other than David Dunning, the professor of psychology at the University of Michigan who is credited with coining the phenomenon along with colleague Justin Kruger.
In 1999, the pair penned a paper called “Unskilled and unaware of it: How difficulties in recognizing one's own incompetence lead to inflated self-assessments.” They tested a large group of people for their abilities in the fields of humor, grammar, and logic. After which, they then asked the participants to self-assess their skills.
Remarkably, those who performed the worst in the test were most prone to overestimating their performance and ability. “Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it,” the study concludes.
The finding appeared to hit a chord with many people and, as you can see in the video below, it's a phenomenon that has been seen time and time again through over 100 studies since.