 This entry expands and updates the “Egoism and Altruism” section in Doris, Stich, Phillips and Walmsley, “Moral Psychology: Empirical Approaches”, The Stanford Encyclopedia of Philosophy (Winter 2017 Edition), Edward N. Zalta (ed.), URL = &lt;https://plato.stanford.edu/archives/win2017/entries/moral-psych-emp/&gt;. Some material in this entry is borrowed from Stich, Doris and Roedder (2010).