Hartvigsen, G., L. Worden, and S.A. Levin. 2000. Global cooperation achieved through small behavioral changes among strangers. Complexity 5(3): 14-19.

ABSTRACT (technical)

Models of the emergence and maintenance of cooperation have generally relied on the assumption that cooperation is costly. We present a new cost-free and spatially-explicit model to investigate conditions that lead to global cooperation. Individuals are represented as simple probabilities of cooperating in the future which are influenced by past experience. Global cooperation is most likely when individuals interact, on average, with strangers (relatively large neighborhoods) and are relatively insensitive to how these neighbors respond. When neighborhoods are small or individuals react strongly to neighbor behavior simulations inevitably end in global defection. Global cooperation can be robust and, with low levels of mutation, resists invasion. We suggest that this simple model may explain cooperation in systems as diverse as biofilm-forming bacteria to human societies.

ABSTRACT (non-technical)

Cooperation in nature and human societies is paradoxical due to the apparent costs of cooperative behavior. Previous models suggest that cooperation arises most frequently when costs are recouped through reciprocity. We present a model that tracks individual players in a spatially defined network that carry a simple probability of cooperating; there are no costs for individuals to cooperate. Global cooperation in our model occurs when individuals interact, on average, with strangers (not neighbors) and are rather insensitive to how these strangers respond. We suggest that this simple model may explain the prevalence cooperation in systems as diverse as bacterial biofilms and human societies.