I can't operate on this boy; he is my son

A man and his son are driving in a car one day, when they get into a fatal accident. The man is killed instantly. The boy is knocked unconscious, but he is still alive. He is rushed to hospital, and will need immediate surgery. The doctor enters the emergency room, looks at the boy, and says...

"I can't operate on this boy, he is my son."

So, the question is, how is this possible? The answer is simple: the doctor is the boy's mother. This riddle has been told for a long time, to illustrate how common gender stereotypes are in our society. What's fun, is to tell this to closet feminists like my mother or sister, and watch them fail to get past the stereotype of thinking "doctor" implies "man".

To say that this riddle is hard because of ingrained gender stereotypes is only half the story. I find it hard and there are several doctors in my family. All of them are women. I have dated more than one (female) trainee doctor.

The riddle also functions on the level of word choice, much like Stupid human tricks such as Ask them to say 'silk'. Ask them to spell 'silk'. Ask them to say 'silk' three times. Ask them "What do cows drink?" .

Look at the words in the sentence "I can't operate on this boy, he is my son." We are being subconsciously cued into expecting a male.

Try this riddle out but change the gender of the child. Use "I can't operate on this girl, she is my daughter", which should in theory introduce no additional expectation about the doctor's gender. It will however be much easier to work out. Or make it neutral, "I can't operate on this kid; this is my child".

To foreigners such as me, there is another problem with this. In my dear mother language, German, nearly all words expressing a vocation or profession exist in a male and in a female form. "A doctor" translates to "ein Doktor", yes; and there is no female equivalent (although it would be possible, see below). But in the sense of "doctor" meant in this story, it would translate to "ein Arzt" (male) or "eine Ärztin" (female). To me as a German, the words "a doctor" look male.

And then there's the problem with knowing (a little) Latin. "Doctor" is a male form. The female form would be "doctrix". Another reason for the words looking male to me.