for a discussion of this by scientists who literally wrote the book on the subject of expert performance. Bear in mind that some domains, notably choosing common stocks in which to invest, have no experts, that is no one who is reliably superior in performance over time.
Empirically, most forms of human greatness ("expertise") are defined as RELIABLY superior performance in the defined domain. See
http://mit.edu/6.969/www/readings/expertise.pdf
for a discussion of this by scientists who literally wrote the book on the subject of expert performance. Bear in mind that some domains, notably choosing common stocks in which to invest, have no experts, that is no one who is reliably superior in performance over time.