Is it that obvious?

I was in Starbucks, minding my own business, earnestly stirring sugar into my latte. When I began the stirring process, I was alone at the condiment counter and was not aware of anyone joining me in the interim. Suddenly a voice boomed, "Can you pass the chocolate when you get a chance?" I grabbed the chocolate and handed it to the guy without thinking, assuming the chocolate incident was now finished. But the guy kept talking, "I find it's better if I add the chocolate *now*." That forced me to look at him - pouring his coffee beverage from one cup into another, stopping halfway to add the chocolate. I felt inclined to reply, "that makes sense, the chocolate will mix better that way." The guy stopped dead in his tracks, mid-pour, looked at me and said "you're a scientist." He then looked me over *very* carefully, seemed to notice I was female, and backed off slightly, "or an engineer." (I mean backed off in the sense that female engineers are not so uncommon in Silicon Valley) I looked straight at him: "Is it that obvious?" He replied, "Yes. You're a scientist/engineer, right?" "I'm a theoretical physicist, working at SLAC. *HOW* did you know?" "Nobody else would have said that (about the chocolate) that way. Only a scientist would talk like that." We then chatted for a bit about SLAC and some piece of equipment a friend of his bought at auction there (we have auctions???), and then I left. Frankly, I don't get it. It's not like I have `Caution: Physicist' tattoed on my forehead! I mean, we spend the better part of our time on this blog convincing you, the public, that us scientists are normal people. **How** did he know???