The Dunning–Kruger effect is a cognitive bias manifesting in two principal ways:

Unskilled individuals suffer from illusory superiority, mistakenly rating their ability much higher than is accurate. This bias is attributed to a metacognitive inability of the unskilled to recognize their ineptitude.

Those persons to whom a skill or set of skills come easily may find themselves with weak self-confidence, as they may falsely assume that others have an equivalent understanding.

David Dunning and Justin Kruger of Cornell University conclude, "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".