1. ©John Wiley & Sons, Inc. 2007 Huffman: Psychology in Action (8e) Evolution of cooperation: Why make friends? Why be nice, making friends must have offered some fitness advantage for our ancestors Evolution of niceness: – Kin selection: being nice to those with similar genetics – William Hamilton: inclusive fitness

2. ©John Wiley & Sons, Inc. 2007 Huffman: Psychology in Action (8e) Kin selection There are a number of examples of what appear to be altruistic behaviors among animals. Most are explainable as examples of kin selection.

3. ©John Wiley & Sons, Inc. 2007 Huffman: Psychology in Action (8e) Reciprocity: You scratch my back I’ll scratch yours Robert Trivers: Reciprocal Altruism Non related individuals sometimes engage in reciprocal arrangements, vampire bats share blood, chimps groom for food

4. ©John Wiley & Sons, Inc. 2007 Huffman: Psychology in Action (8e) Indirect reciprocity: being nice to the nice Richard Alexander: Fitness benefits of a good reputation Some animals are sensitive to reputation and restrict reciprocal interactions to only those who have a history of playing fair

5. Strong reciprocity: Upholding social norms Resurrection of group selection: Groups with more cooperative norms more likely to survive then those without. Evidence – People uphold social norms even a personal cost (ultimatum games) – Bias toward kin is a group-based form of selection – Evidence of group competition in ancestral past – “leveling” effects of “punishment at a distance” Paul Bingham’s “stoning” hypothesis Major figures: Herb Gintis, David Sloan Wilson and others

6. Prisoner’s Dilemma A “game” that pits defensive self-interest against cooperative tendencies. Used in lab studies of the evolution of cooperation. Asks question: When will self-interested agents risk cooperation in order to achieve a greater payoff.

7. When can cooperative strategies evolve? When does cooperation have higher fitness than selfishness? Tit for tat or direct reciprocity Forgiveness Indirect reciprocity Spatial selection Multi-level selection

8. Tragedy of the Commons

9. Avoiding the Tragedy Factors that increase cooperation on use of common “goods” 1. Authoritative information on the state of the resource 2. Public generosity (reputation) 3. Being watched