Weitz Group @ Georgia Tech Theoretical Ecology and Quantitative Biology

New PNAS article on an "Oscillatory Tragedy of the Commons"

Posted by jsweitz

Prof. Weitz is the first author on a game-theory paper on an “oscillatory tragedy of the commons” - which just came out in PNAS. This is joint work with Ceyhun Eksin, Keith Paarporn, Sam Brown and William Ratlcliff, all at Georgia Tech:


In it, we model how strategies and the environment interact, both co-influencing the other. The presumption is that actions change the environment, whether a water resource, the state of a disease, antibiotic supply, or even institutions.

The state of the environment influences incentives to “cooperate/help” or “defect/cheat”. When the environment or “commons” is replete, there are strong incentives to cheat. This cheating can degrade the environment.

Over time, the environment can become depleted as each individual acts out of their own self-interest, and, in the long run, all individuals are worse off than had they coordinated. More troubling, the environment “collapses” too.

With a degraded commons, the question becomes: do incentives change? If they do, then individuals may start to cooperate. The cumulative actions of individuals working for the common good – and in their own self-interest - can restore the commons. But even if they do, the time to climb out of the depleted state can be much longer than the time it took to fall in.

The following principle in our model made it possible for individuals to restore the commons:

“A small group of cooperating individuals can, over time, change the social and environmental context for all and for the better.”

In the model, this cooperation had to take place even when others cheated and even when the environment was degraded.

Read more here: