An optimistic computer model

I found this bit towards the end of the fifth chapter of The Logic Of Life encouraging. It's obviously based on game theory, and I'm sure you can pick holes in it, but it cheered me up today!

The computer randomly pairs up people each 'day' (actually, many times a second). The computer gives them a simple choice: act honestly or act corruptly. If both sides of the pair act corruptly, both enjoy a kickback; if only one acts corruptly and the other honestly, the crook will go to jail.

The magic of the computer model is seeing how quickly the artificial world can change. At first, it is populated by self-interested crooks, with a few honest citizens sprinkled among them. The few honest citizens don't respond to incentives; irrationally, if heart-warmingly, they will always act honest. The crooks do respond to incentives, being corrupt or honest depending on whether they think the other side will reciprocate. The chances of honesty being the best policy are quite small at first, and many days go by with corruption thick in the air and honest folk unable to stem the tide.

But when... crooks decide that even other crooks will decide to act honestly they will do the same. That fear of an outbreak of honesty can spring up suddenly as the result of a few random events, a few honest citizens clustered together creating the impression of a legal crackdown. After a long period of pure corruption, [the] model displays a change even more dramatic... suddenly, very quickly, everybody in the world decides to be honest. The moment the process starts it is impossible to stop: offering a corrupt deal becomes irrational and suddenly the world is full of crooks who have decided that honesty is the best policy. It is a self-fulfilling decision. The cascade of tiles on the computer screen changes colour abruptly as honesty breaks out everywhere.

[The] model is still a vast simplification, of course. But it does provide a hint at why some societies do seem to move from awful corruption to relative lawfulness very suddenly. The model confirms that the transitions can be dramatic; they can have tiny causes, or even no cause at all, just being the product of random events. Each rational individual decision changes the decisions of others, just as small stones rolling down a hill can build into a landslide. In life, as in the model, the collective output of such interactions may not resemble the typical individual's desires, even if it is a change for the better.