The Evolution of Cooperation

部分参赛算法

• TIT FOR TAT
• FRIEDMAN: once got defected, defect from then on (totally unforgiving)
• JOSS: TIT FOR TAT but occationally defect when should have cooperated
• HARRINGTON: 前 15 名中唯一一个 non-nice 程序。随着进化，一开始有增长，但是当它可以加害的受害者被淘汰后，它自己也被淘汰。

  The ecological analysis shows that doing well with rules that do not score well themselves is eventually a self-defeating process.

摘抄

Chapter 2 The success of TIT FOR TAT

P38

A major lesson of this tournament is the importance of minimizing echo effects in an environment of mutual power. When a single defection can set off a long string of recriminations and counterrecriminations, both sides suffer.

P54

What accounts for TIT FOR TAT's robust success is its combination of being nice, retaliatory, forgiving, and clear. Its niceness prevents it from getting into unnecessary trouble. Its retaliation discurages the other side from persisting whenever defection is tried. Its forgiveness helps restore mutual cooperation. And its clarity makes it intelligible to the other player, thereby eliciting long-term cooperation.

Chapter 6 How to Choose Effectively

P110 The advice

1. Don't be envious.

   Asking how well you are doing compared to how well the other player is doing is not a good standard unless your goal is to destroy the other player. ... Given the strategy of the other player, are you doing as well as possible? Could somone else in your situation have done better with this other player? (P111)

   TIT FOR TAT 没有赢下一局比赛，但是总分最高。在非零和博弈中，你不需要比对手得分高来赢得高分。This is especially true when your are interacting with many different players.

2. Don't be the first to defect.
3. Reciprocate both cooperation and defection.

   The precise level of forgiveness that is optimal depends upon the environment. In particular, if the main danger is unending mutual recriminations, then a generous level of forgiveness is appropriate. But, if the main danger is from strategies that are good at exploiting easygoing rules, then an excess of forgiveness is costly. (P120)

4. Don't be too clever.

P123

There is an important contrast between a zero-sum game like chess and a non-zero-sum game like the iterated Pisoner's Dilemma. In chess, it is useful to keep the other player guessing about your intentions. But in a non-zero-sum setting it does not always pay to be so clever. In the iterated Prisoner's Dilemma, you benefit from the other player's cooperation. The trick is to encourage that copperation. A good way to do it is to make it clear that you will reciprocate.

P182

The foundation of cooperation is not really trust, but the durability of the relationship.