THE PREVALENCE OF FREE RIDING

The prospects for the spontaneous emergence of cooperation in n-person prisoner's dilemmas are studied within an evolutionary framework. Both purely cooperative regimes and states representing a mix of conditionally cooperative with noncooperative strategies tum out to be possible outcomes of the selection process, but only the latter correspond to evolutionarily stable strategies. Two-person games differ qualitatively from games with three or more players in that they are more propitious to cooperative regimes. Spontaneous cooperation in general collective-action games therefore appears less likely than much of the recent literature seems to indicate.