Standard game theory assumes purely selfish or rational individual behavior, which means every player will just act to optimize one's own payoff function regardless of the effects that their choices may have on the others. However, many phenomena where people do care about others' benefits can be observed in the real world. Experiments also show discrepancy between the experimental results and the theoretical prediction with the assumption of selfishness. Various explanations with "not entirely selfish" players have been proposed.
The selfish outcomes have been observed to be drastically downgraded from the optimal one in several natural games. Thus, our goal is studying the impact of partially altruistic/spiteful behavior on the outcome of games, and specifically the social welfare. We develop
and analyze a game-theoretic model with partially altruistic/spiteful players situated in an economic or social network environment. We show the impacts of such model on (atomic) congestion games, non-atomic congestion games (i.e., routing games), network vaccination games, and auctions.