The evolution of cooperation

Altruism and the selfish gene n Altruism: benefit b to recipient at cost -c to the donor

Altruism and the selfish gene n Altruism: benefit b to recipient at cost -c to the donor n `get the altruism out of altruism...´ (Trivers)

Altruism and the selfish gene n Altruism: benefit b to recipient at cost -c to the donor n `get the altruism out of altruism...´ (Trivers) n kin selection n Hamilton´s rule: c< b.r

Altruism and the selfish gene n Altruism: benefit b to recipient at cost -c to the donor n `get the altruism out of altruism...´ (Trivers) n kin selection n Hamilton´s rule: c< b.r n in humans co-operation among non- relatives

Darwin: n The small strength and speed of man, his want of natural weapons, etc., are more than counterbalanced... by his social qualities, which led him to give and receive aid from his fellow men.

Cooperation among non-relatives n Direct reciprocation and the Prisoner´s Dilemma n Indirect reciprocation n Public Goods

n Consequently, theories of evolution which, in accordance with the philosophies inspiring them, consider the mind as emerging from the forces of living matter, or as a mere epiphenomenon of this matter, are incompatible with the truth about man. Nor are they able to ground the dignity of the person.

Reciprocity n Reciprocal altruism...the trading of altruistic acts in which benefit is larger than cost, so that over a period of time both parties enjoy a net gain. (Trivers)

The Prisoner´s Dilemma game n To cooperate or to defect n (example: cooperate means to give a gift of value b at cost -c)

Prisoner´s Dilemma

The iterated Prisoner´s Dilemma n probability w for another round n (for instance, toss a coin, stop game if 6) n shadow of the future (Axelrod)

The iterated Prisoner´s Dilemma

n Generous Tit For Tat n p close to 1 n q sizeable n two zones

The iterated Prisoner´s Dilemma

n Heteroclinic network n A = Tit or Tat n B = Firm But Fair n C = Bully n D = AllD

The iterated Prisoner´s Dilemma

Pavlov n Cooperate if other player used same move as yourself in previous round n reinforcement principle: repeat former move after high payoff n Pavlov is error-correcting n Pavlov is stable n Pavlov cannot invade population of defectors

Pavlov

n Simple learning rule n stable, error-correcting n but needs retaliator to prepare the ground

Indirect reciprocity n few rounds, as donor or receiver n never with the same partner twice

Indirect reciprocity n R. Alexander: Indirect reciprocity.. involves reputation and status, and results in everyone in the group continually being assessed and reassessed.

Indirect reciprocity n R. Alexander: Indirect reciprocity.. involves reputation and status, and results in everyone in the group continually being assessed and reassessed. n Cooperation channelled towards cooperative members

Indirect reciprocity n score: increases by 1 if help is given, decreases by 1 if help is withheld n score 0 at birth

Indirect reciprocity n score: increases by 1 if help is given, decreases by 1 if help is withheld n score 0 at birth n strategy k: give only if recipient has score at least k n k>5: always defect n k<-5: always help

Indirect reciprocity

n cooperation based on discrimination n but not stable (can occasionally break down)

Indirect reciprocity

Indirect Reciprocity

William D. Hamilton The theory of many-person games may seem to stand to that of two-person games in the relation of sea-sickness to a head-ache!