Time's Role in the Tragedy of the Commons

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The "tragedy of the commons" is an economics theory, first published by Garrett Hardin in the journal Science in 1968. It is referred to as a tragedy because is describes the dilemma arising from the situation in which multiple individuals, acting independently and rationally consulting their own self-interest, will ultimately deplete a shared limited resource even when it is clear that it is not in anyone's long-term interest for this to happen. The concept is often cited in connection with sustainable development, and indeed, Jennifer Jacquet in large-scale cooperation dilemmas such as climate change.

Jacquet is an assistant professor at NYU and environmental scientist interested in human behavior. Together with colleagues from the Max Planck Institute, she recently designed a study examining the factor of time in the "tragedy of the commons", published in Nature last year.

"The factor of time is often overlooked in game theory", says Jacquet, "but the tension that exists between the present and future self is very interesting."

The experimental design had six students in a room together without them being able to see or communicate with each other. Each student was given 40 Euro. They were then given the option of donating 0, 2 or 4 Euro to a collective climate change mitigation fund over the course of ten rounds.

The money they donated was used to place an ad warning against climate change in a local paper. If they managed to raise 120 Euro over the ten rounds, each student received an additional 45 Euro. The socially optimal outcome therefore would have been for every student to donate 20 Euro and walk away with 65 Euro.

This is the key to collaboration: there is a sacrifice, but if everyone is willing to make this, there is also a mutual benefit. Unfortunately, the downside is that the benefit is equal for all, whereas sometimes the sacrifice is unevenly distributed. In some groups one student donated more than others, for instance "and we can imagine at the end they were not as satisfied as others".

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However, what was really interesting in the experiment, was the addition of the factor time. They manipulated the experiment to yield three further set-ups. In the first, students would get receive the additional 45 Euro benefit after one day delay; in the second, after a seven week delay; and in the third they would not receive a monetary benefit at all but rather that money was used to plant trees. This later condition is probably the closest to climate change mitigation, as our actions today are geared towards benefiting future generations.

Seven out of eleven groups studied achieved the benefit threshold in the one day delay condition. Four out eleven achieved the benefit threshold in the seven week delay condition. In the third condition, however, no group achieved the 120 Euro threshold. The number of 0 Euro donations was highest in this condition.

"Media framed this experiment as pessimistic, but I think the fact that even one group almost achieved the contribution threshold in the last condition is very interesting," Jacquet says. She believes that had the participants been allowed to interact with one another, more would have collaborated successfully.

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