Punishment and Cooperation
One of the core assumptions of the proposition that moral punishment is an instinct is that punishment stimulates cooperation among group members. This chapter starts with supernatural punishment, illuminating that whereas belief in heaven has no effect on national crime rates, belief in hell reduces crime rates. Also, in economic games, the possibility to punish increases the cooperation that people display. These effects emerge because punishment increases deterrence, communicates moral norms, and instills trust. The chapter then notes that punishment has facilitated cooperation among strangers as people started forming large states, and that people become more punitive in situations that required unconditional cooperation and self-sacrifice for the group (i.e., war). These findings suggest that punishment indeed stimulates cooperation in social groups.