There seems quite a bit of difference between introspective evaluation of one's own abilities and accomplishments, a bit of self-doubt, and imposter syndrome's clinically persistent internalized fear of being exposed as a "fraud". I see this as a spectrum all people fall on to some degree or another with the possible disorder at both ends where those extremes impact many aspects of life:
Of course, I'm not a mental health professional and claim no real expertise here but find it interesting how this parallels the Autism Spectrum. I'm familiar with that spectrum due to interaction with friends and family being informally and formally 'on the spectrum'.
So far, for what self-diagnostics are worth; no less and no more: I feel I fall on the 'healthy self-evaluation' middle ground. I don't feel I am more intelligent than others (as I feel there are so many types of intelligence) and I don't feel I have deceived anyone otherwise. I do not feel my success is by luck, privilege, etc. - but by intense subject interest and willingness to put time towards my interest.
That said, I do feel from time to time that others wishing to enter the field overestimate how much 'intelligence' has been and will be a key factor in my successes. I recognize others may not have the aptitude to do the things I have done - but I am also keenly aware - others have aptitudes I do not. I'm not satisfied with my tasks unless I understand the mechanisms at play well enough to explain them to a child - but I would definitely apply to a job for which I did not seem a 'perfect fit' based upon the laundry list laid out in the advertisement. 🙂
David Taylor, CISSP CEH Microsoft Almuni Gulf War Veteran