I think that's a study of a problem that is relatively common: that people of low intelligence will sometimes think they are however much smarter, as well as more knowledgeable (when they are neither of the two). I am not sure how this applies to intelligent people, though perhaps the Dunning-Kruger study examined that issue. In some cases, those people are also trying to compensate for other kinds of difficulties, beyond merely cognitive abilities and experience. The Dunning-Kruger effect also relates to psycholological issues, which I've not addressed directly. One can extend that psychological assessment to physical anomalies, like sawing off one's tallywhacker, but physical anomalies aren't appropriately addressed in the Dunning-Kruger study. I would think that anyone who chops off his John Thomas is lacking in intelligence, experience and sanity, but if he(she?) is hired to do a job that primarily requires knowledge, then intelligence and sanity and the status of one's ding dong (or lack thereof) might not relate to his(her?) competence on the job.