## Friday, June 29, 2007

### Voluntary Punishment

Most social tendencies in people have easily identifiable evolutionary roots. For example, a group of psychopaths would have a hard time getting very far, while a group of altruistic people would ensure the survival of the group. Very simple mathematical models can be made of these types of dynamics that often show exactly the expected behavior. Some behaviors, however, are a little more tricky. Punishment is one of those. In group endeavor, there are those who will give up time and resources to punish those who they feel are not properly participating. Where is the advantage in taking time and effort to punish someone else?

A recent study published in the journal Science (click here for the Scientific American story) has, for the first time, mathematically modeled why punishment is important. Using a simple model, a group was divided into 3 sub-groups: cooperators, defectors (those who are trying to catch a free ride), and punishers. The cooperators tend to become defectors at a rate that is inversly proportional to the number of punishers and proportional to the number of defectors (no one wants to be working hard when everybody else is getting a free ride) and punishers at a rate that depends on how many defectors there are. The defectors become cooperators at a rate that depends on the number of punishers. The punishers become cooperators based on the number of defectors on the premise that defectors would resist punishment by putting pressure on the punishers to stop punishing them.

The funny thing is that in this model, the defectors always end up dominating. After transient behavior dies down, the steady state probability is 100% defectors. This would obviously be a big problem for anything the group tried to accomplish as it would be dominated by people who were trying to get a free ride.

The really interesting thing to me was that if you add a fourth group to the system, it changes everything. If you make another group of non-participants and make it so that defectors, cooperators, and punishers leave the group when it is not doing well (i.e. defectors dominate) and non-participants join the group when it is doing well (i.e. cooperators and punishers dominate), then a totally new dynamic emerges. Essentially, unless the punishers are too mean or the benefits of joining the group when it is successful are too small, a balanced distribution occurs where punishers and cooperators dominate, but small percentages of defectors and non-participants remain.

What really strikes me about this simple model is at it drives right to the heart of my opinions about free enterprise. In a forced model, it is in everyone's best interest to try to get as much as possible and contribute as little as possible, even if the organizers contribute tons to resources to punishing those who do that. For example, if you make doctor' visits free for everyone, what you'll end up with is everyone wanting to go to the doctor far more than they need to. On the other hand, if people have to chose to be a part of the group and potentially sacrifice to do so, they tend to appreciate what they have more. If people have to pay insurance premiums, they tend to be more careful with their doctor's visits.

I know this study was just a simple model, but I believe it hit a profound truth about human nature: if we are forced to do something we won't do it as well as if we chose to, even if there are obvious benefits to choosing to do that thing. Communism is not effective because no matter how much punishment there is, in the end it pays to slack off. Capitalism, on the other hand, works because it's voluntary. If it doesn't benefit you to be a part of a company or health insurance plan or book club, you can leave it. That freedom to leave seems to make all the difference in the world.