The prisoner’s dilemma

The paradox of buses and congested traffic

I’ve got this very interesting book called This Book Does Not Exist: Adventures in the Paradoxical. I haven’t actually read that much of it yet, but one paradox – the prisoner’s dilemma – has struck me as intriguing and very relevant to everyday life.

It goes like this: You and I have both been arrested for a crime and are being interrogated in separate cells. Both of our sentences depend on whether each of us confess to our crime. There are four different scenarios:

If you confess but I don’t, you will go free while I serve a five-year prison sentence.

If I confess but you don’t, I will go free while you serve a five-year prison sentence.

If we both confess, we will each serve a two-year sentence.

If neither of us confesses, our crime cannot be proved. In that case, we will both be jailed for six months on a lesser charge.

You have to choose what to do without knowing my decision, and vice versa.

Assuming you only care about yourself in this situation, the logical thing to do would be to confess. Either you’re completely freed if you’re lucky, or you get a two-year sentence if I confess as well – whereas if you don’t confess, you have no chance of getting off and you may well be banged up for five years.

However, the best possible outcome for both of us together is if you don’t confess and neither do I. In this case, we get away with only a half-year sentence each. If we both take the rational option for ourselves, we take two-year prison terms and endure worse punishment than if we had taken the irrational option and refused to confess.

Unfortunately, we are unlikely to both refuse confession and a lot more likely to both plead guilty, taking the logical option for ourselves – which, ultimately, makes things worse for the both of us.

This is often the case in life. The book gives the very familiar example of whether to take the bus or the car to work. If not many people take the bus, your best option for yourself is to drive, which is quicker and means you don’t have to wait at the bus stop. However, if lots more people took the bus that would be a lot more convenient for you and everyone else, because the emptier roads and more regular services (because of the higher demand) would make the journey quicker. But even then going by car is quicker, but if everyone else starts to take the car for that logical reason you go back to square one…

This could also be applied to voting. If you support a minor party, but don’t want one of the major parties to get in, the rational decision would be to tactically vote for one of the main parties that’s closer to your views. But if everyone voted with their hearts, that would be best, because the party would at least have a far greater influence and you’d be more likely to get your first choice.

Like with the prisoners, the only way to beat this paradox is to communicate with the other voters. If you managed to get lots of like-minded people together to vote for your first choice (this is possible at least in your own constituency, especially with the advance of the Internet), you could actually get the best outcome.

There are so many other incidences where this paradox has an effect. There is only one way to beat it. Would we all be better off individually if we just pulled together and agreed to do what’s in the wider interest? I think so.

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One thought on “The prisoner’s dilemma

  1. Pingback: Planes, trains or automobiles? « Present Day

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