Princess Bride Iocane Powder: Anticipating rivals


20120522-143633Most students quickly grasp the concept of game theory–figuring out what your opponent is likely to do helps you decide what you ought to do. As this clip shows, however, failing to understand the real decision choices to be made can lead to deadly, but funny results. In class, after introducing simultaneous vs. sequential games, I show the clip, pausing it just before the 2:11 mark. At this point the poison is in the goblet, and I ask the students who haven’t seen the movie which goblet they think is poisoned. I record answers, and then show the clip (up to anywhere between 4:45 and 5:02). I then ask if they were surprised. I then show the remainder of the clip, and we discuss what mistake Vazinni made. Students see the real payoff matrix as: a) if I (Vazinni) guess wrong, I’m dead; b) If I guess right, then the Dread Pirate Roberts knows it too has incentive to kill me before he dies. I only live if Iocane powder kills instantly. My correct answer can only be not to drink either goblet if I want to live. After watching this video clip and class discussion, students can:

  • identify what is a simultaneous decision
  • identify the true payoffs in a payoff matrix
  • understand the value of changing the game
  • never get into a ground war in Asia (okay, just kidding about that one).

Princess Bride fans might also appreciate this clip illustrating non-substitutability…

Contributed by Russ Coff and Jay Janney

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