The role of fairness motives and spatial considerations in explaining departures from Nash equilibrium: stationary and evolutionary lessons from 2x2 games

Substantial evidence has accumulated in recent empirical works on the limited ability of the Nash equilibrium to rationalize observed behavior in many classes of games played by experimental subjects. This realization has led to several attempts aimed at finding tractable equilibrium concepts which perform better empirically, often by introducing a reference point to which players compare the available payoff allocations, as in impulse balance equilibrium and in the inequity aversion model. The first part of this paper is concerned with reviewing the recent reference point literature and advancing a new, empirically sound, hybrid concept. In the second part, evolutionary game theoretic models are employed to investigate the role played by fairness motives as well as spatial structure in explaining the evolution of cooperative behavior.