[juancn]

Impostor syndrome is kind of a corollary of the Dunning–Kruger effect. Since you know a lot about some discipline, you're better able to judge your gaps in knowledge, and you assume others know as much as you (because of a gap in knowledge on what others know, so you extrapolate from your on level of knowledge on that discipline, which is high).

The converse also happen, where you know enough to overestimate your knowledge of the thing.

https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

[username90]

According to the Dunning-Kruger effect a majority of people overestimates themselves, so if most people thinks they have impostor syndrome then a lot of them are wrong.

[juancn]

No. By definition, if you overestimate yourself, you don't have impostor syndrome in that particular discipline.