Actual skill is hard to observe directly, especially early in a relationship or a meeting. So people lean on a proxy instead: how someone carries themselves. A 2012 study by Cameron Anderson and colleagues, published in the Journal of Personality and Social Psychology, found that confident behavior reliably earned people higher status within a group — independent of whether that confidence was actually backed by real ability.
The mechanism is efficiency, not gullibility. Judging someone's actual competence takes time, context, and often expertise the observer doesn't have. Judging their confidence takes seconds — posture, tone, pace of speech, willingness to answer without hedging. The brain substitutes the easy signal for the hard one, and usually doesn't notice it's made the swap.
This doesn't mean confidence is fake or undeserved in any individual case — many competent people are also confident. It means confidence functions as a status signal on its own, which is exactly why it keeps working on people who've been told, explicitly, not to fall for it.