Homo Moralis—Preference Evolution Under Incomplete Information and Assortative Matching


  • Ingela Alger,

    1. Toulouse School of Economics (LERNA, CNRS), 21 Allée de Brienne, 31 015 Toulouse cedex 6, France and Institute for Advanced Study in Toulouse; ingela.alger@tse-fr.eu
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  • Jörgen W. Weibull

    1. Stockholm School of Economics, P.O. Box 6501, 113 83 Stockholm, Sweden and Institute for Advanced Study in Toulouse; jorgen.weibull@hhs.se
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    • We thank the editor and three anonymous referees for helpful comments. Earlier versions of this manuscript have been presented at an NBER workshop on culture and institutions, at Tel Aviv University, Stockholm School of Economics, IMEBE 2012, University of Southern California, UC Santa Barbara, UC Riverside, UC San Diego, the Becker-Friedman Institute conference “Biological Basis of Preferences and Behavior,” University of Warwick, Ecole Polytechnique (Paris), Lancaster University (UK), University of Oxford, Institute for International Economic Studies (Stockholm), Toulouse School of Economics, GAMES 2012, ITAM, Frankfurt University, University of York, and University of Zürich. We thank Rajiv Sethi, Immanuel Bomze, Avinash Dixit, Tore Ellingsen, Jens Josephson, Wolfgang Leininger, Klaus Ritzberger, François Salanié, and Giancarlo Spagnolo for comments. This research received financial support from the Knut and Alice Wallenberg Research Foundation. Ingela Alger is grateful to ANR, Carleton University, and SSHRC for financial support and to the Stockholm School of Economics for its hospitality.


What preferences will prevail in a society of rational individuals when preference evolution is driven by the resulting payoffs? We show that when individuals' preferences are their private information, a convex combination of selfishness and morality stands out as evolutionarily stable. We call individuals with such preferences homo moralis. At one end of the spectrum is homo oeconomicus, who acts so as to maximize his or her own payoff. At the opposite end is homo kantiensis, who does what would be “the right thing to do,” in terms of payoffs, if all others would do likewise. We show that the stable degree of morality—the weight placed on the moral goal—is determined by the degree of assortativity in the process whereby individuals are matched to interact.