If you answered, "the surgeon can't operate because SHE'S the boy's mother," then you're correct!
If, like me and most everyone to whom this riddle is presented, you never would picture the surgeon as a WOMAN, then you got the riddle wrong.
What does this prove, you ask?
Well, from my colleague's point of view, it proves that we are absolutely trapped and defined by language--that every word inhabits a matrix of images and associations to which we are culturally attuned and from which we can never free ourselves. It follows then the only way to change our perspective and/or paradigm, is A) to acknowledge the inordinate subliminal power of words and B) to consciously choose our language as an act of rebellion against the dominant paradigm.
What does this prove from my point of view?
That A) I'm just as unconsciously ruled by all the sad -isms (sexism, racism, classism, age-ism, etc.) as anyone else; B) that American society really is still sexist when it comes to career expectations for men and women (in case anyone thinks otherwise); and C) that maybe, just maybe, the one place we can actually effect some tangible change is through language.