A cellular model of prisoners dilemma for “prodding gratuity”

摘要

Repeated prisoner’s dilemma (RPD) is an evolutionary game, extensively utilised for modelling socio-economic dynamics.Such an instrument was used in order to investigate co-operation in different interesting aspects and strategies, e.g., gratuity (Bruni, 2008) [2], in terms of co-operation, that privileges a collective advantage.This work explores RPD extension to a spatial context (SRPD) by a stochastic distribution of agents with different strategies in the space of a Cellular Automaton (CA) according to the Nowak approach (Nowak and May, 1993) [22]. This approach coincides with SPD extension to SRPD. In SRPD, each cell is occupied by one agent, that relates with all other agents in neighbourhood cells in terms of RPD classic payoffs and symmetries. Results show that the SRPD convergence to total co-operation or defection is very rapid (more than RPD), but some values of payoff generate an interesting chaotic evolution of the system. Furthermore, introduction of new behaviours of agents through altering payoffs and symmetry characterises this our model. In such conditions, unexpected emergence of co-operative behaviours was detected for agents with complex strategies, in spite of their reduced conditions of increasing own payoff.