Engines of Our Ingenuity

No. 875:
THE PRISONER'S DILEMMA

by John H. Lienhard

Click here for audio of Episode 875.

Today, let's help the prisoner sort out his dilemma. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Scholars invent a shorthand for the great problems of human behavior. They talk about Hobson's Choice, Occam's Razor, and Gresham's Law. One of the most disturbing of these conundrums is the Prisoner's Dilemma.

Two prisoners have committed a crime. Now they're held in separate cells. Each can either confess and plead for a light sentence or claim innocence and blame the other.

If one blames and one confesses, the blamer fares well and the confessor suffers. If each blames the other, it goes hard for both. In aggregate, they do best when each confesses.

Now: You and I are those prisoners. Oh, we may not be in jail, but the same moral dilemma comes up all the time in everyday life. I think of times I've seen two students turn in identical tests. How do people really behave in such moments?

The Prisoner's Dilemma is mired in questions of honesty and compassion -- as well as self-interest. And remember: Most participants have to deal with each other afterward. Since the pair does best when both confess, the Dilemma blurs the line between the best interests of the individual and of society.

Philosophers, psychologists, and mathematicians have all wrestled with implications of the Prisoner's Dilemma. Now computer modelers and animal behaviorists are in the act. They set up a dizzying array of games, tests, and simulations to see how both people and animals react to such a bind.

Those experiments make some things clear. The long-range behavior in society is imitative. You imitate what works. You go for cooperation. You confess. But when you do, you lay society open to the one person who exploits things to his own advantage. He poses a terrible threat to cooperative behavior. Both animal populations and computer models for human behavior show that we'd better punish him. If we don't, we're in trouble.

If you let me get away with condemning you, while you confess, then you undermine the learning that sustains cooperative behavior. The computers say that if you let me blame you twice, you get what you deserve the second time. In that sense, I hold society together by keeping you alert to my evil.

Still, the computers cannot capture all the dimensions of human behavior. They don't account for backbiting and vendetta. Anger can lead people to seek revenge and damn the personal cost. But we also transcend simple tests with the power of friendship.

We violate simple cause and effect. We defy the calculus of behavior. We negate that logic in the very act of letting the Prisoner's Dilemma touch our conscience -- and disturb our sleep.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Beardsley, T., Never Give a Sucker an Even Break. Scientific American, October 1993, p. 22.

Frohock, F.M., Rational Association. Syracuse: Syracuse University Press, 1987.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

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