Humans are often happy to share food with their friends, but what about animals? Contrary to their reputation, vampire bats are surprisingly social and generous, and a well-fed bat will even ...

In The Evolution of Reciprocal Altruism (1971), Robert Trivers writes that many aspects of the human emotional system evolved to regulate the reciprocity system: "… friendship, dislike, moralistic ...

Is it just me, or do we all find ourselves, every now and again, feeling like we need to apologize? In my life, this often arises in situations like the following: “Sorry I was late – I really ...

Guest Opinion. Altruism is helping without a benefit and sometimes at a risk to one’s self. Animals helping others of their own species makes sense to perpetuate the species or help continue their own ...

Citations: Leider, Stephen, Markus Mobius, Tanya Rosenblat, Quoc-Anh Do. 2009. Directed Altruism and Enforced Reciprocity in Social Networks. Quarterly Journal of Economics. (4)1815-1851.