[more adv. alt. notes]
In the Prisoner's Dilemma, the egoist has a dominant strategy of defecting. Given that, there is no way that altruism in the Dilemma can help the altruist in a one-shot game. The egoist will defect regardless, and the altruist will wind up with either his or her worst or second possible payoff. (footnote--There are five additional games in which the egoist also has a dominant strategy and thus cannot be affected by altruism on the part of the other player. In those games, though, unlike the Prisoner's Dilemma, the dominant strategy for the egoist is either clearly optimal for both players or very possibly optimal. Accordingly, these five games--which could be termed Harmony Games because of their benevolent payoff structure--do not present the significant difficulties for egoism that the Prisoner's Dilemma does.)
In six other games, though, the egoist has no dominant strategy. In all of these games, altruism can be potentially useful to the altruist as well as to the two players together. Three of the six games may be called assurance games. In these games--Trust, Schelling, and Stag Hunt are the labels that will be used here--both players earn their highest payoffs if they both trust. But if the other player does not trust, you are better off if you also do not trust. (footnote--The three games differ among themselves in two major respects. In two of them--Trust and Stag Hunt--if you trust when the other player does not you get your worst possible payoff, while in the third, Schelling, you get your third worst payoff. In two of them--Schelling and Stag Hunt--both players get their second-best payoffs from both not trusting and going it alone, while in one, Trust, both players get their third-best payoffs from both going it alone.)
In the assurance games, altruism has the potential to be helpful if it leads to the altruist committing to trust. Such a commitment leads the egoist to trust, since trust-trust is the best outcome for both players.
Interestingly, full altruism does not do the trick in leading to commitment to trust. As we will explore further, only a form of selective altruism that values the trust-distrust payoff for the trusting player highly will work.
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