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
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
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
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