Unsourced:

How many people here, when you’re holding a baby near a stairwell or an open window, suddenly have a little thought where you go, “Oh, I think I just imagined throwing the baby out the window. I think I’ve got a desire to throw babies out the window. I don’t think I should be holding Mary’s baby.” “Mary, would you like to take the baby?”

And I would ask the audience, and I would go through all these different things, and I’d say, “Who’s had those thoughts?” And some people would put their hands up, and then I would—sometimes no one would—and then normally I’d pick on one person with a hand up, and I’d say:

“Now you, I have to warn everyone about. I have to tell the people the truth about you. You—you are the safest pair of hands to hold a baby.”

And then I would explain to the audience that those thoughts—those impulsive thoughts—are actually public information films.

So when you’re holding a baby by an open window or a cliff, your brain makes a little film that goes:

“You’re holding a baby by a cliff. Don’t throw the baby over the cliff.”

But it’s delivered so quickly that the brain confuses it for a desire.