Dude Thinks He Can't Sing - Classic Dunning–Kruger effect

The Dunning–Kruger effect is a hypothetical cognitive bias stating that people with low ability at a task overestimate their own ability, and that people with high ability at a task underestimate their own ability.

As described by social psychologists David Dunning and Justin Kruger, the bias results from an internal illusion in people of low ability and from an external misperception in people of high ability; that is, "the miscalibration of the incompetent stems from an error about the self, whereas the miscalibration of the highly competent stems from an error about others".[1] It is related to the cognitive bias of illusory superiority and comes from people's inability to recognize their lack of ability. Without the self-awareness of metacognition, people cannot objectively evaluate their level of competence.