What game theory says about negotiating with terrorists
April 19, 2018 § 33 Comments
Two members of a criminal gang are arrested and imprisoned. Each prisoner is in solitary confinement with no means of communicating with the other. The prosecutors lack sufficient evidence to convict the pair on the principal charge. They hope to get both sentenced to a year in prison on a lesser charge. Simultaneously, the prosecutors offer each prisoner a bargain. Each prisoner is given the opportunity either to: betray the other by testifying that the other committed the crime, or to cooperate with the other by remaining silent. The offer is:
If A and B each betray the other, each of them serves 2 years in prison
If A betrays B but B remains silent, A will be set free and B will serve 3 years in prison (and vice versa)
If A and B both remain silent, both of them will only serve 1 year in prison (on the lesser charge)
The thing to notice about the Prisoner’s Dilemma as a one-off situation is that each prisoner is better off betraying the other, no matter what the other prisoner does.
However real life does not consist of a single one-off choice, and the PD can be re-imagined as an ongoing game with repeated rounds, where years in prison are replaced by points in the game: “less years in prison” equals more points, if you will, and the more points you get the better you are doing in the game. Each round of the game a player chooses whether to cooperate or defect, and the game is played for an indeterminate number of rounds. The goal is to maximize how well you are doing “against the House” not against the other player: to minimize total years in prison, if you will.
In this iterated Prisoner’s Dilemma, wherein two players engage in the game repeatedly, actual human beings use the game itself to communicate with each other and collaborate. A very effective strategy in an iterated Prisoner’s Dilemma (played against another human being) is not betrayal but “tit-for-tat“: cooperate with the other player unless he defects; if he defects then ‘punish’ him by defecting on the next round. In this way a pair of “prisoners” can optimize their score against the house over time, by learning to cooperate.
Iterated “games” are fundamentally different from one-off situations. This is why intelligent decision makers learn, over time, not to negotiate with terrorists. Terrorist negotiations may (or may not) change the outcome in a particular case, for better or worse. (The choice there is ultimately up to the terrorist, not the negotiator, since presumably the negotiator is not proposing to do something evil himself).
But choosing to negotiate with terrorists in general is what gives terrorists power; and in an open-ended iterated “game” this means that in the long run the evil party wins. Each negotiation increases the power of “team terrorist”. If this goes on long enough morality will invert: “team terrorist” will be seen as victims rather than perpetrators; opposing their wanton slaughter of the innocent will come to be seen as oppressive tyranny; and the mountains of corpses will pile up to the sky. (I say “will” as if this were a future prediction rather than a retrospective).