Conversely - we tell people who are speaking in public to "Show confidence" - or in job interviews "Hire people who are confident"

We've also pushed back "The more a person knows, the less confident they are" - Dunning Kruger - often used to dismiss over confident people - points out that people are really confident, at first, then that confidence drops away, markedly, but it rebuilds (slowly).

That last rise in confidence is what (I believe) people use as a heuristic on the likely level of knowledge possessed by the speaker (AI or human)

Most engineers know, though, that overconfident people are toxic - the difference between arrogance and genuine confidence in the answer is incredibly difficult to define.