Alice is in a tight situation involving Bob. Maybe Bob wants money from her, or has a gun pointed at her head, or is just plain annoying. Alice points past Bob's shoulder and yells, "Hey, what's that over there?!?", or "Look! A [insert improbable thing here]!" Bob looks. Alice legs it. In the subversion, Bob doesn't look, but instead mocks Alice: "You'll think I'll fall for that?" or "That's the oldest trick in the book!" Unfortunately for Bob, deciding not to look drastically ramps up the probability that the thing Alice described is there, and it'll be something he's not going to like.