It depends on what I say, I suppose.
When people hear that I study computer science, they start talking to me about, well, computers. About which I must say, I don’t really know much more than anyone else; computer science (or at least my corner of it) is no more the study of computers than astronomy is the study of telescopes. If the conversation is around people who do know things about computers, this can be particularly embarrassing.
When people hear that I study math, they often say something like “Oh, I can’t do math”, possibly accompanied by “You must be smart then”. This irks me greatly. Do you ever hear anyone say “Oh, I’m not smart enough for linguistics/geology/music theory/journalism/…”? Barring medical tragedy, people, as a general lot, are capable of doing whatever it is their interests drive them to spend time learning to do.
When people hear that I study logic, they also say “You must be smart then”, though probably for different reasons, reasons elucidated by the other response, “I didn’t know there was any such thing. What is there to study in logic?”. Which is actually a fair question; I have no reason to dislike this except my own shameful inability to usefully communicate the answer.
All these are but minor statistical flukes, though, in comparison to the following law of physics:
When people hear I’m from New Jersey, they always, always ask “Which part?”. I slowly run through in various levels of specificity from “North Jersey” down through to the corner of the county, waiting for a response, till finally they say “Oh. I have a friend/cousin/pen pal/family pet from New Jersey, but they live in [some place as unfamiliar to me as North Dakota]”.