# Considerate Equilibrium

Hoefer, Martin, Penn, Michal, Polukarov, Maria, Skopalik, Alexander and Vöcking, Berthold (2011) Considerate Equilibrium. At 22nd International Joint Conference on Artificial Intelligence (IJCAI), Barcelona, Spain, 16 - 22 Jul 2011.

We study the existence and computational complexity of coalitional stability concepts based on social networks. Our concepts represent a natural and rich combinatorial generalization of a recent notion termed \emph{partition equilibrium}~\cite{Feldman09}. We assume that players in a strategic game are embedded in a social (or, communication) network, and there are coordination constraints defining the set of coalitions that can jointly deviate in the game. A main feature of our approach is that players act in a considerate'' fashion to ignore potentially profitable (group) deviations if the change in their strategy may cause a decrease of utility to their neighbors in the network. We explore the properties of such \emph{considerate equilibria} in application to the celebrated class of \emph{resource selection games (RSGs)}. Our main result proves existence of a super-strong considerate equilibrium in all symmetric RSGs with strictly increasing delays, for \emph{any} social network among the players and feasible coalitions represented by the set of cliques. The existence proof is constructive and yields an efficient algorithm. In fact, the computed considerate equilibrium is a Nash equilibrium for a standard RSG, thus showing that there exists a state that is stable against selfish and considerate behavior simultaneously. Furthermore, we provide results on convergence of considerate dynamics.