An animal that decides not to pick a fight is, in most cases, simply worried about the risk of getting injured—not about some abstract “norm against violence.” Likewise, an animal that shares food with non-kin is typically just angling for future reciprocity—not following some “norm of food-sharing.” The incentives surrounding true norms are more complex. When we do something “wrong,” we have to worry about reprisal not just from the wronged party but also from third parties.5
