evolution of social behavior: reciprocal altruism & cheater detection

mutualism vs manipulation vs reciprocation

Mutualism

• interaction between individuals of the same or different species that results in mutual positive effects on the reproduction and/or survival of the interacting individuals

• no cost-benefit asymmetry (both individuals benefit)

Manipulation

• coercive or other manipulative behaviors

• benefits to recipient > costs of providing benefit

Reciprocation

• net costs at the time when benefit is provided but this is offset by subsequent benefits

  • expectation of being paid off later on

kin selection & inclussive fitness theory cannot explain altruism among non-kin → solution:

reciprocal altruism theory

• fitness benefits of altruism to both parties (‘i’ll scratch your back and you’ll scratch mine’)

• single act of altruism turn into reciprocity and cooperation

conditions for reciprocation

1. Individuals must associate (zich verenigen met) for long-enough periods of time to develop reciprocal interactions

• live in the same group & regular contact

2. The likelihood of one individual performing some social exchange with another should be predicted on the basis of their past associations

3. The roles of giver and receiver should reverse at least once

4. The short-term benefits to the recipient are greater than the costs to the donor

5. Givers should be able to recognise and expel cheaters from the system

problem of altruism

possibility to cheat → take benefit but fail to reciprocate

• frequency dependent selection: whether altruism or cheating is favored depends on how frequent each strategy is in the population

  • a lot of altruists → cheating is beneficial

• can be studied with game theory

prisoners dilemma (game theory)

illustrates the problems of altruism/cooperation & cheating

• Each prisoner must choose to betray the partner or cooperate with him; the decision of each is kept quiet. What should they do?” → dilemma bcs you don’t know what your parent will do

  • nash equilibrium

Nash equilibrium

What is the best decision, given what everybode else is doing, that cannot be bettered?

What does prisoners dilemma sugest that is the best strategy?

DO NOT COOPERATE → confess

• to avoid high cost of being betrayed

• <=> not how people behave in social relationships!

problem with normal prisoners dilemma (+ solution)

one time contact → not a good model of social relationships

iterated prisoner’s dilemma

• two players play prisoners dilemma more than once → previous actions are remembered → change strategy acoordingly

  • cheaters can be punished

What is the succesfull strategy to play in an iterated prisoners dilemma

“tit for tat - strategy” = cooperates on the first move and subsequently echoes what the other player did on the previous move

• cooperate as long as the other cooperates, defect/punish when cheate

all the best performing strategies were nice = never the first to defect

eg shoot & miss strategy in war

Why is the TFT strategy so succesful?

evolutionary stable strategy (ESS)

• Encourages cooperation (starts by cooperating)

• Punishes for cheating immediately

• forgiving: if the other party begins to cooperate again, is cooperative and not vindictive (wraakzuchtig)

How does TFT explains why people often cooperate even in one-shot games of prisoner’s dilemma? (which is non-rational)

our ancestors were unlikely to find themselves in positions where their social behavior had no possible future repercussions

• ancestral environment = small group of individuals who came into contact => actions had consequences

=> suggest that receprocation has a long evolutionary history & that engaging in mutual receprocation could be a ESS & therefore selected for

How well do we recognize cheaters in advance

we can detect cuses of trustworthiness

• most likely non-verbal

• eg. prisoners dilemma: after discussiond people had to predict the move their oppont would made → predictions were accurate (much better than by chance)

Which factor predict co-operation

phenotypic similarity

• familiarity enhance trust

• related to carrying similar alleles

Why do we act altruisticly even in cases where the immediate pay off would be higher if we cheat?

to protect our reputations

• long-term repercussions of loss of reputation can lead to decreased fitness

(eg. in prisoners’ dilemma 75% cooperates, event hough it is better to be selfish)

Which factors have an effect on altruism? (dictator gamee)

if players meet each other → more fairly

if participants remain anonymous → more cheating and less generosity

How can the concept of fairness be modulated?

ultimatum game

• participant is given a sum of money & he can devide it over him & the other player

• other player accepts or declines

  • accepts → both players get the money

  • declines → both players receive nothing

What is the expectation vs outcome of the Ultimatum game?

expectation

• giver: offer a sum well below 50%

• receiver: accept any offer above 0 (better than nothing)

outcome 

• givers offer around 50%

• more than half of the receivers do not accept offers less than 20%

What is the seed of moral behavior?

fairness

• not unique to humans (‘if two individuals conduct the same behavior, they should be rewarder equally’)

Why has morality evolved?

regulate relationships and facilitate group living & cooperation

• personal moral values

• community-based rules and regulations

• religions 

• law

→ morality drives us to cooperate & natural selection, in humans especially, might have favoured cooperation

in-group and out-group bias

Categorization

• why? → easier and faster to make predictions about how things are and behave

• how → typicality (shared traits) + assumed group memberships

• effect: 

  • In-group loyality

    • favor individuals that belong to the same group

    • real / imagined threats to the group → group identity (us vs them)

  • out-group hostility (= vijandigheid nr buitenstaanders)

    • Tendency to be wary of and label as cheaters all who have not been proven otherwise

      • → Negative stereotypes and xenophobia towards strangers

      • → can lead to extreme violent acts towards out-group individuals

    • might have been useful in the ancestral environment

      • smaller coalitions within larger groups → group identity ('us')

        • devide resources into their own groups

        • favors for in-group members

Robbers cave exp.

Two groups of boys played competitive games against each other

• quickly resorted to hostility and violence

• Groups could only unite when they had a common enemy

  • 3th group broke watter suplie down & in order to fix this the two groups have to work together → common enemy needed

Note: experiment manipulated the boys to feel hostility towards each other, originally the boys wanted to befriend the other group → experimenters did all they could to turn the boys towards each other (eg. they broke their camp & then told them that this damage was done by the other boys-group)

• we don't now how the boys would have behaved if they hadn't been manipulated

• => shows that under manipulating (especially from authorities) peoples behaviour can be affected

prison exp. (‘das experiment’)

Arbitrary division of young men into prisoners and guards => unhumane treatment of prisoners in just few days

• experiment had to be ended in 6days

• criticism: manipulation of the pp (especially the guards) → encouriging them to stick to the rules & show the prisoners their right places

  • => we won't know how they really would have behaved

  • => shows again the power of manipulation