Two basic tenets of the Walrasian model, behavior based on self-interested exogenous preferences and complete and costless contracting have recently come under critical scrutiny. First, social norms and psychological dispositions extending beyond the selfish motives of Homo economicus may have...

A number of outstanding puzzles in economics may be resolved by recognizing that where members of a group benefit from mutual adherence to a social norm, agents may obey the norm and punish its violators, even when this behavior cannot be motivated by self-regarding, outcome-oriented...

Experimental and other evidence demonstrates that many individuals willingly give to strangers, reward good deeds and punish violations of norms by others even at a significant cost to oneself, and favor fellow group members over others. These behaviors exhibit aspects of both altruism ­...