1. Cooperation Overview of the Day The evolution of cooperation Reciprocal altruism Cheater detection Friendship

2. The Evolution of Cooperation zHow could cooperation evolve when among humans who are motivated by self-interest? zThe relation of cooperation to self-interest yKin Selection (kin-based altruism) yReciprocal Altruism zThose who cooperate are more likely to survive and reproduce yThe rabbit and deer problem

3. Reciprocal Altruism yGiving help with the expectation that the other will return the favor in the future. xBoth parties benefit (as long as cooperation is reciprocated) xGain in trade--each party receives more in return than it costs to deliver the benefit yThe theory of RA was developed by Robert Trivers (1971)

4. Evidence for Reciprocal Altruism: The Prisoner's Dilemma zThe problem of cooperation as modeled in the PD simulation zOne-shot opportunity z200 interactions (14 entries) zIndefinite interactions (62 entries) zIn both iterated simulations the winning strategy was “tit for tat”

5. Tit for Tat z(1) Cooperate on the first move and (2) reciprocate on every move thereafter ynever be first to defect yretaliate only after the other has defected ybe forgiving--if a defector starts to cooperate, the reciprocate zDo unto others… Forgive … (sound familiar?)

6. Cooperation (tit for tat) in Nature zVampire bats and blood zMale baboons and help getting sex zFemale vervet monkeys: grooming and calls for help

7. Reciprocal Altruism and the Problem of Cheating zRA works best when people don’t cheat ycheating: when people take the benefit but do not pay the cost of reciprocation zTherefore, need to detect cheaters zCheater detection mechanism : yrecognize different humans yremember histories of interaction ycommunicate what you want yunderstand what others want yrepresent costs and benefits of items

8. Detecting Cheaters zWe do it all the time ysome examples... zProblem solving--much easier to solve problems of social exchange (than, say, abstract logical problems) ythis suggests a long evolutionary history of reciprocal social exchange in humans (fundamental to our social life)

9. Where Evolutionary Explanations of Altruism Run into Trouble: The Case of Good Samaritans zGood Samaritans: People helping non-kin with no expectation of the favor being returned. yExamples zHow can we explain Good Samaritans?

10. Friendship zShould altruism be defined in terms of costs or benefits? zWhat is a friend, what is friendship? zIs friendship based on social exchange or something else? yFriendship altruism is based on delivering benefits (not because you are incurring a cost) xFor example, picking up a second bottle of milk for a friend when you go grocery shopping

11. Altruism in And of Clay We are Created zWhat concepts from EP could explain why Rolf Carle risked life and limb, why he suffered as much as he did, to help the little girl? yReciprocal altruism? xWas there a tit for tat? yFriendship xdelivering benefits zIs this a case of unselfish altruism, and therefore not explainable by EP?

12. The Banker’s Paradox and Friendship zThe banker’s paradox: those who need the money most are the worst credit risks, and those who need it least are the best risks. Therefore banks tend to lend money to those who need it least. zWhich friends are you most likely to help? Those who are poor or good credit risks? zWhich is more true to life? y Nobody knows you when you’re down and out yA friend in need is a friend indeed

13. The Grameen Bank, and the Banker’s Paradox zOriginated in 1976/1983 in Bangladesh to provide credit to poor villagers yBy 1998: 1,118 branches, service to 38,766 villages y2.3 million borrowers y$2.5 billion in cumulative loans y$185 million in savings y98% loan collection rate

14. 95% of The Grameen Bank’s Borrowers are Women zNo collateral zLoan acceptance based on peer group yLoan based on approval of a small peer group of borrowers yDefault of one individual to to repay results in all group members become ineligible for further loans zOne of the most successful 3rd world economic development programs to date

15. Will Cold, Rational Strategies Win You More Friends? zTo gain more friends, should you follow the advice in How to Win Friends and Influence People? or just be yourself? ySmile yCall people by their name yMake sure people don’t cause people to lose face

16. What about Buss’ s Advice? yHighlight your unique attributes yRecognize undervalued attributes in others yCultivate specialized skills that make you more irreplaceable ySeek out groups that value you yAvoid groups that don’t value you yDrive off rivals

17. Summary and Projects zThe evolution of cooperation zReciprocal altruism zCheater detection zFriendship zYour projects (time is moving fast): yFocus yQuestion that can be addressed with data yWhat type of data will you collect? yHow will your data answer your question?

18. For Next Time zAggression, Buss, Cpt. 10; Allende, The Schoolteacher’s Guest