The actual payoff matrix the experimenters used is here: http://www.plosone.org/article/slideshow.action?uri=info:doi/10.1371/journal.pone.0008483&imageURI=info

The actual payoff matrix the experimenters used is here: http://www.plosone.org/article/slideshow.action?uri=info:doi/10.1371/journal.pone.0008483&imageURI=info:doi/10.1371/journal.pone.0008483.t001 http://www.plosone.org/article/slideshow.action?uri=info:doi... It does follow the rules of prisoner's dilemma, as far as I can tell. (Found via the link to the original paper, http://www.plosone.org/article/info:doi/10.1371/journal.pone.0008483#pone-0008483-t001 http://www.plosone.org/article/info:doi/10.1371/journal.pone...)