©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

©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.

©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

©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

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”

hypothesisMajor figures: Herb Gintis, David Sloan Wilson and others

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.

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

Tragedy of the Commons

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