Sharing Pastures and the Tragedy of the Commons

Altruism is a thing we do in groups, out of a sense of cooperation. During the holiday seasons many of us feel – and act upon – some tingly sensation that compels us to do something nice, something selfless, something altruistic. There may be many reasons why we act so, including cultural, societal, neural biological reasons. Most likely, though, it’s because “tis the season” for giving. When seasons change, and giving becomes less a part of the spirit that is summoned from the depths of our crusty souls, we likely act in cooperative ways as a result of what behavioral economists call Altruistic Punishment.

We see examples of Altruistic Punishment all the time. In Behavioral Economics: When Psychology and Economics CollideScott Huettel shares the story of the Cleaner Fish and Client Fish. Cleaner Fish, who usually live and work in groups, survive by eating the bacteria off of larger, singular Client Fish. The arrangement is a mutually beneficial and symbiotic relationship that helps the Client Fish stay healthy and provides food and protection for the Cleaner Fish. However, there are some Cleaner Fish who will occasionally take a slightly more delicious nibble of the Client Fish. (Ouch!) When this happens the other Cleaner Fish in the group will regulate; they will chase off the rogue snacker until she gets her act together. Why do they chase off one of their own community members? Much like Yelp!, Client Fish keep track of the groups of Cleaner Fish and will avoid those with bad reviews. So for the good of the group – so all the Cleaner Fish don’t have their food supplies constantly swimming off elsewhere – the rogue helper is punished. The Cleaner Fish and Client Fish are great illustrations of Altruistic Punishment: maintaining cooperation and order in the community by punishing those whose singular acts are causing harm to the greater good.

Thing about Altruistic Punishment is that for it to work, in groups, the cost of punishing has to be relatively low for Cleaner Fish and the cost for the the rogue Client Fish has to be relatively high. Oh, and there has to be good, upstanding Client Fish willing to chase after the rogues. When this breaks down some rogue Cleaner Fish will get fat of of Client Fish, but the rest of the group will suffer.

And this is the tragedy of the commons. 

“A problem for the cost-benefit theory is that my benefit can be your cost. Consider the well-known tragedy of the commons. There is a pasture that is available to everyone. Each shepherd will want to keep as many sheep in the pastre as possible. But if everyone increases the number of sheep in the pasture, at some point overgrazing occurs, risking everyone’s livelihood. The problem – the tragedy – is that for each individual shepherd the gain of adding one sheep is equal to +1, but the contribution to degradation of the commons is only a fraction of -1 (minus one divided by the number of shepherds who share the pasture). My pursuit of self-interest combined with everyone else’s pursuit of their self-interest results in ruin for us all.” (Mindware, Nisbett, pp 81-82)

For a global pasture, the cost to an individual shepherd is 1/7,000,000,000. The cost to the pasture, and all the other shepherds, adds up quickly.

This is where Altruistic Punishment comes in. To keep the Client Fish food source around, to save the pasture, the rogue Cleaner Fish and the over-grazing shepherds, some folks need to be chased. Whether its guns, burning hydro carbons, finance reform…

And so one must consider: what kind of group member am I? A rogue or an enforcer? Is there room for something else besides? Something that benefits the greater good…

Feature image, “Elacatinus evelynae”, by LASZLO ILYES (laszlo-photo) from Cleveland, Ohio, USA – Flickr. Licensed under CC BY 2.0 via Commons –

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