Discussion on question by Donald: Is it correct to call oneself "Doctor/Scientist/Mathemathician" simply because one has a PhD in that field?

Over a very long life I don't recall anyone holding a Ph.D. referring to themselves as "doctor". (I'm in Canada, should it matter.) Perhaps diploma-mill Ph.D.'s are more inclined to do that.

I am surprised at so many of the comments/answers here. I am in northeast U.S., and here the title "doctor" is thrown around like candy. When I was a university student, most of the professors preferred (or even insisted) on being called "Doctor" no matter their field. I made the mistake of referring to a physicist as "Mr. X" once and received a stern warning about title, that I was always to refer to him as "Dr. X." Even outside academia, many people around here insist on being referred to with their "Doctor" title. This doesn't really answer, hence comment, but should be enlightening to you.