Game theory and Cooperation in Social Systems

It’s almost 2am, but I have been thinking about a summary of a recent Nature paper I read while I was in Boston visiting MIT. I had picked up the article in MIT Tech Talk on a whim during a visit to the Stata Center where MIT’s CSAIL laboratory is located.

This article helped me start thinking about the conundrum of:
– why there are so many people willing to spent so much time shuffling and passing links to other people?
– why people write Wikipedia articles when they can spend time doing other things?
– why do users tag photos and URLs when the majority of the benefit is for others to find these items more easily?
In short, why is it that entities in social systems cooperate, especially when the benefit to oneself is not entirely clear at all?

Turns out researchers of microbes have been thinking about some of these cooperation problems as well. “One of the perplexing questions raised by evolutionary theory is how cooperative behavior, which benefits other members of a species at a cost to the individual, came to exist.” They have used yeast as a model for understanding what might be happening. Sucrose is not yeast’s preferred food source, but some yeast cells will metabolize it when glucose is not available, but the sugar diffuse away, and other free-rider yeast cells (lazy bums!) then benefits from the sugar for free.

Well, if the sugar diffuse away completely, then there is no reason to be the ‘cooperating’ cell to spent all that energy to benefit others. It gets really interesting when the cooperating yeast cell have preferential access to, say, 1 percent of the sucrose they metabolize. This slight advantage not only allow for the cooperating cells to compete effectively against the cheaters, but also enable the entire yeast community to benefit from having sucrose as an alternative food source. Moreover, no matter what the starting numbers of yeast cells, they end up into an equilibrium state with just the right amount of cooperating cells and cheaters present after some evolutionary period. The MIT team used game theory to model this entire process, and showed why it works the way it does. Darn cool!

This got me thinking about agents in a social system sometimes behave in similar ways, and can be modeled using game theory. I’m sure some of this has already been done. This sort of study is common in behavioral economics, for example. But how does it apply direct in social web system modeling? How can it help explain, for example, the tagging behavior of users in flickr? Perhaps the little bit of benefit that the user gains from organizing photos that she owns or have found is enough to turn them into ‘cooperating’ agents, from whom other freeriders obtain benefit. Moreover, the idea could be used to model why there are just the right pareto-balance (and power-law distributed) of cooperating agents and freeriders in a social web system.


Jeff Gore, Hyun Youk & Alexander van Oudenaarden.
Snowdrift game dynamics and facultative cheating in yeast.
Nature advance online publication 6 April 2009 | doi:10.1038/nature07921

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