Heh, I guess that would be true, wouldn't it! (Except, presumably, with a higher percentage of brunettes, who I imagine don't break into song quite as often? :) ) I have no other experience quite like this, myself -- my discipline isn't super-high in non-white people, but they do pop up often enough that it isn't weird.

Now if I were black... I can't remember ever seeing a black person in my field. I knew one at my entire graduate school (knew her through choir) and she would get asked things like, "Are you the janitor's wife?"