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Copy of Robert Axelrod- Reciprocal Altruism
Transcript of Copy of Robert Axelrod- Reciprocal Altruism
Kuhn, Steven, "Prisoner's Dilemma", The Stanford Encyclopedia of Philosophy (Spring 2009 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/spr2009/entries/prisoner-dilemma/>.
Koeing, Walter D. "Reciprocal Altruism in Birds." Hastings Reservation and Museum of Vertebrate Zoology, Carmel Valley, California. Web. <http://www.nbb.cornell.edu/wkoenig/k038ta_88.pdf>. Bibliography The concept was originally made by Robert Trivers to explain the Evolution of Cooperation when concerning "tit for tat" acts used in game theory. Cooperation in organisms has been a difficulty for evolutionary theory since Darwin. On the assumption that interactions two people occur on a probabilistic basis, a model is developed based on the concept of an evolutionarily stable strategy in the context of the Prisoner's Dilemma game. Was originally made by Merrill Flood and Melvin Dresher working at RAND in 1950.
It shows why two individuals might not cooperate, even if it appears that it is in their best interest to do so. Prisoner's Dilemma Two men are arrested, but the police do not possess enough information for a conviction. Following the separation of the two men, the police offer both a similar deal—if one testifies against his partner (defects/betrays), and the other remains silent (cooperates/assists), the betrayer goes free and the cooperator receives the full one-year sentence. If both remain silent, both are sentenced to only one month in jail for a minor charge. If each rat out the other, each receives a three-month sentence. Each prisoner must choose either to betray or remain silent; the decision of each is kept quiet. The game interested game theorists like Dr. Axelrod, and from these basics, a more general form of the game emerged. In 1984 Dr. Robert Axelrod held a tournament where he invited many players to give their strategies which they used to play against others for 100 rounds. The winner was a strategy called Tit for Tat, developed by Anatole Rapoport. The concept was to cooperate on the first move and then do whatever your opponent did on the last move. The Tournament There are two players (1 and 2). Each player has two choices in an interaction - “Snitch” or “Not to Snitch”.
Each player makes his choice at the same time and only knows each others moves at the end of a turn. At the end of a turn,
each player receives something as described below, depending on what each of them did.
1. If player 1 snitches and player 2 cooperates, player 1 gets the Temptation to snitch for a payoff of 5 points while player 2 receives the Sucker’s payoff of 0 points.
2. If the reverse happens, the exact reverse in terms of score happen.
3 . If both cooperate they get the reward for cooperating payoff of 3 points each
4. If they both defect they get the punishment for Mutual Snitching payoff of 1 point. To snitch or not to snitch? That is the question. Conditions necessary for an instance of reciprocal altruism:
1. the behaviour must reduce a donor's fitness relative to a selfish alternative;
2. the fitness of the recipient must be elevated relative to non-recipients;
3. the performance of the behaviour must not depend on the receipt of an immediate benefit;
4. conditions 1, 2, and 3 must apply to both individuals engaging in reciprocal helping.
Two additional conditions necessary for reciprocal altruism to evolve:
A mechanism for detecting 'cheaters' must exist.
A large (indefinite) number of opportunities to exchange aid must exist. Axelrod concluded that the lessons were that the
strategies needed to be:
1 ) Nice - It will not defect before its opponent does.
2) Punishing - The successful strategy, though nice, needed to punish dissenting behavior. This is a very bad choice, as “nasty” strategies will ruthlessly exploit such softies like parasites.
3) Forgiving - Another quality of successful strategies is that they must be forgiving. Tit for tat, for example, punishes dissent, but when the other comes back with cooperation, it again cooperates. This stops long runs of
revenge and counter-revenge.
4) Consistent – Strategies that had random elements, tended to show retaliation. Consistent strategies worked well in getting cooperation from other strategies. Vampire Bats Meercats Monkeys