Non-Excludable Public Good Experiments revised October 2003, forthcoming in Games and Economic Behavior.

We conduct a two-stage game experiment with a non-excludable public good. In the first stage, two subjects choose simultaneously whether or not they commit to contributing nothing to provide a pure public good. In the second stage, knowing the other subject's commitment decision, subjects who did not to commit in the first stage choose contributions to the public good. We found no upport for the evolutionary stable strategy equilibrium, and the ratio of subjects who did not commit to contributing nothing increased as periods advanced; that is, the free-riding rate declined over time.Furthermore, this behavior did not arise due to altruism or kindness among subjects, but from spiteful behavior of subjects..

Published: Timothy Cason, Tatsuyoshi Saijo, Takehiko Yamato and Konomu Yokotani, 2004. "Non-Excludable Public Good Experiments," Games and Economic Behavior, Vol. 49(1), pp. 81-102.
http://www.sciencedirect.com/science/article/pii/S0899825604000065