Lecture 19- Human cooperation

Question 1

What is Hamilton’s rule?

Answer 1

-Selection will favour cooperative, or altruistic behaviour if:

br - c > 0 where,

b = benefit to beneficiary;

c = cost to donor;

and r = coefficient of relatedness (degree to which actor and beneficiary share genes)

• This ‘rule’ makes the simple prediction that individuals are more likely to direct cooperative or altruistic behaviour toward relatives than toward non-rela-ves.
• the more related the more likely to cooperate
• the inequality has to exceed 0
• r is very important but costs and benefits are also important
• important in insect systems since many do not reproduce whereas in vertebrate species the helpers can, usually just younger individuals waiting for territories etc.

Question 2

How doe Hamilton’s rule apply to humans?

Answer 2

• may have applied when humans lived in relatively small kin-based groups – humans as cooperative breeding families
• but modern, complex human societies couldn’t be more different – groups of cooperating humans are rarely related
• why cooperate? -families are often not as involved in raising offspring -

Question 3

What is the argument about the evolution of cooperation in humans?

Answer 3

It is often argued that a key feature of human society is the profound level of cooperation exhibited among unrelated individuals. In general, cooperation is not predicted by conventional natural selection: individuals are unlikely to enhance the reproductive success of others if it creates a fitness cost to themselves

Question 4

What are the possible reasons for people to cooperate?

Answer 4

Two solutions

• kin selection — cooperation may evolve among relatives because any genetic basis to a tendency to help relatives is likely to be carried by both the donor and recipient
• game theory — a mathematical tool that helps explain collective behaviour by the interactions of the individuals involved

Question 5

What is meant by the Dunkirk spirit?

Answer 5

• in 1940, many civilians assisted, at great risk to themselves, in the evacua-on of allied troops from Dunkirk by flo-llas of pleasure craJ and working barges
• theoretical models suggest that parochial altruism (the combination of in-group altruism and out-group hostility) provides a selective advantage to groups, resulting in the coevolution of parochial altruism and intergroup conflict by group extinction through conquest and assimilation

-very risky behaviour -

Question 6

What is the setup of the field experiment in Northern Ireland?

Answer 6

A field experiment

• many years of sectarian conflict in Northern Ireland
• geographic regions separated along religious affilia-on
• opportunity to inves-gate generosity (coopera-on) toward in-group and out-group

-Methods -Surveyed households, asking if they would care to donate to a primary school within their locality, a primary school outside their locality, or a neutral charity (Save the Children). Other details obtained

Question 7

What were the results of the field experiment in Northern Ireland?

Answer 7

Conflict

• clear evidence for the existence of parochialism: individuals 25% more likely to donate to an in-group school than an out-group school (note, location of the school not specified)

-Cooperation

• no evidence that ‘threat’ influenced within-group cooperation;
• SES was better predictor (income, education, etc).

Question 8

What is the setup of prisoner’s dilemma?

Answer 8

Two prisoners

• unable to communicate with each other
• must choose to (a) testify against the other (defect) or (b) remain silent (cooperate) Their sentence depends upon what both prisoners claim
• if one testifies against the other, and the other remains silent, the former goes free and the other gets 3 years
• if each testifies against the other, then both get two years
• if both remain silent, both get one year

-But cooperation occurs between naïve players – perhaps indirect reciprocity is important: helping someone or refusing to do so, may have an impact on one’s reputation within a group.

Question 9

What is connection of prisoner’s dilemma and reputation?

Answer 9

• Players decisions about whether to donate were always anonymous within the game -Individuals were given £3, paired and randomly designated donor (give 50p) or receiver (obtain £1). Giving something increases an image score, which was displayed at the end of the session.
• The receivers’ image score had an influence on the donors’ decision: receivers who got something had a higher image score than those that got nothing. Similarly, the donors’ decisions were also influenced by their own image score: donors with a low image score were more likely to give something (and thus improve their image score)
• then another scenario when the individuals then played the prisoner’s dilemma with their final image score revealed
• reputation image influences long term outcome of playing prisoner’s dilemma (direct reciprocity game)

Question 10

What happened in the Prisoner’s Dilemma when the pay offs etc. were altered in each game?

Answer 10

-Pay-offs of each iteration in the Prisoners’ Dilemma game; two games were played that alter the relative pay-offs for defection and punishment. Cooperation means paying a cost c for the other person to get benefit

b, defection means earning a pay-off d at a cost d to the other person

-here you could punish the other individuals as well

a, All-out cooperation.

b, Punish and perish.

c, defection for defection can sometimes restore

d turning the other other cheek can also restore cooperation

e mutual punishment is mutual destruction

f punishment does not restore cooperation

g guns don’t kill people, people kill people, an unprovoked firs strike destroys cooperation

-There is no correlation between the frequency of playing cooperation or defection and the average pay-off at the end of a game