The theory of norm psychology proposed in Sripada & Stich, “A Framework for the Psychology of Norms,”  suggests that people will often internalize norms that reduce their own biological fitness.  It might be thought that no such psychological mechanism could possibly evolve.  But that would be a mistake.  In this talk I’ll explain why it was all but inevitable that natural selection would lead to norm psychology in our species, once we had acquired the ability to learn from one another.  The account I’ll offer explains why many human norms foster cooperative or pro-social behavior.  It also explains why many human norms lead to ethnic hatred and morally repugnant behavior.  If the account is correct, these norms will be very difficult to dislodge.   Though I’ll present a brief sketch of the Sripada & Stich theory at the beginning of the talk, the paper, which is available on line, is strongly recommended as background reading.