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In what is arguably the greatest superhero movie of all time, the Joker (played by the late Heath Ledger) always seems to be one step ahead of the law. The strategic interactions between the police and the conniving villain are an illustration of game theory in action.
Near the end of movie, the Joker rigs two full passenger ferries to explode at midnight and tells the passengers that if they try to escape, the bomb will detonate earlier. To complicate matters, one of the ferries is filled with civilian passengers and includes a number of children, while the other ferry is transporting prisoners. Each ferry is given the chance to save itself by hitting a detonator button attached to the other ferry.
The Joker’s plan sets up a prisoner’s dilemma between the two boats and an ethical experiment. Are the lives of those on the civilian boat worth more than those of the prisoners? The Joker’s intention is to have one of the ferries blow up the other, and thereby create chaos in Gotham City.
In the payoff table, the dominant strategy is to detonate the other boat. Since failing to detonate the other boat results in death—either because your ferry blows up at midnight, or the other boat detonates you first. In this scenario, the only chance of survival is if your ferry detonates the other ferry first. As the scene unfolds and the tension builds, the passengers on both boats realize their plight and wrestle with the consequences of their decisions. Gradually, everyone becomes aware that the dominant strategy is to detonate the other boat. What is interesting is how the civilians and prisoners handle this information.
What actually happens? Rent this movie and watch the scene as a game theorist; it will give you a new appreciation for the film.
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