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20200531 The Evolution of Cooperation




The main idea of this book is to present results of author’s research on cooperation that was conducted using tournament of computer game based on prisoner’s dilemma. The result consistently demonstrated that the best strategy is always TIT-FOR-TAT starting with default cooperation. Author also presents brief overview of history of cooperation, its evolutionary significance, and provides recommendation on how to expand cooperation.


I: IntroductionChapter 1: The Problem of Cooperation
Here author discusses the problem of cooperation: why would egoists cooperate without central authority that would force them to do this? Author bases his search for solution on analysis of prisoner’s dilemma as game:

Author also provides here the review of book’s content.

II: The Emergence of Cooperation
Chapter 2: The Success of Tit FOR Tat in Computer Tournament
This chapter explores the emergence of cooperation through the study of what is a good strategy to employ if confronted with an iterated Prisoner’s Dilemma. This exploration has been done in a novel way, with a computer tournament. Professional game theorists were invited to submit their favorite strategy, and each of these decision rules was paired off with each of the others to see which would do best overall. Amazingly enough, the winner was the simplest of all strategies submitted. This was TIT FOR TAT, the strategy which cooperates on the first move and then does whatever the other player did on the previous move. A second round of the tournament was conducted in which many more entries were submitted by amateurs and professionals alike, all of whom were aware of the results of the first round. The result was another victory for TIT FOR TAT! The analysis of the data from these tournaments reveals four properties which tend to make a decision rule successful: avoidance of unnecessary conflict by cooperating as long as the other player does, provocability in the face of an uncalled for defection by the other, forgiveness after responding to a provocation, and clarity of behavior so that the other player can adapt to your pattern of action. These results from the tournaments demonstrate that under suitable conditions, cooperation can indeed emerge in a world of egoists without central authority.

Chapter 3: The Chronology of Cooperation
To see just how widely these results apply, a theoretical approach is taken in chapter 3. A series of propositions are proved that not only demonstrate the requirements for the emergence of cooperation but also provide the chronological story of the evolution of cooperation. Here is the argument in a nutshell. The evolution of cooperation requires that individuals have a sufficiently large chance to meet again so that they have a stake in their future interaction. If this is true, cooperation can evolve in three stages. 1. The beginning of the story is that cooperation can get started even in a world of unconditional defection. The development cannot take place if it is tried only by scattered individuals who have virtually no chance to interact with each other. However, cooperation can evolve from small clusters of individuals who base their cooperation on reciprocity and have even a small proportion of their interactions with each other.

2. The middle of the story is that a strategy based on reciprocity can thrive in a world where many different kinds of strategies are being tried.

3. The end of the story is that cooperation, once established on the basis of reciprocity, can protect itself from invasion by less cooperative strategies. Thus, the gear wheels of social evolution have a ratchet.

III: Cooperation Without Friendship or Foresight
Chapter 4: The Live-and-Let-Live System in Trench Warfare ion WWI
Chapter 4 is devoted to the fascinating case of the “live and let live” system which emerged during the trench warfare of World War I. In the midst of this bitter conflict, the front-line soldiers often refrained from shooting to kill— provided their restraint was reciprocated by the soldiers on the other side. What made this mutual restraint possible was the static nature of trench warfare, where the same small units faced each other for extended periods of time. The soldiers of these opposing small units actually violated orders from their own high commands in order to achieve tacit cooperation with each other. A detailed look at this case shows that when the conditions are present for the emergence of cooperation, cooperation can get started and prove stable in situations which otherwise appear extraordinarily unpromising. In particular, the “live and let live” system demonstrates that friendship is hardly necessary for the development of cooperation. Under suitable conditions, cooperation based upon reciprocity can develop even between antagonists.

Chapter 5: The Evolution of Cooperation in Biological Systems
Chapter 5, written with evolutionary biologist William D. Hamilton, demonstrates that cooperation can emerge even without foresight. This is done by showing that Cooperation Theory can account for the patterns of behavior found in a wide range of biological systems, from bacteria to birds. Cooperation in biological systems can occur even when the participants are not related, and even when they are unable to appreciate the consequences of their own behavior. What makes this possible are the evolutionary mechanisms of genetics and survival of the fittest. An individual able to achieve a beneficial response from another is more likely to have offspring that survive and that continue the pattern of behavior which elicited beneficial responses from others. Thus, under suitable conditions, cooperation based upon reciprocity proves stable in the biological world. Potential applications are spelled out for specific aspects of territoriality, mating, and disease. The conclusion is that Darwin’s emphasis on individual advantage can, in fact, account for the presence of cooperation between individuals of the same or even different species. As long as the proper conditions are present, cooperation can get started, thrive, and prove stable. While foresight is not necessary for the evolution of cooperation, it can certainly be helpful.

IV: Advice for Participants and Reformers
Chapter 6: How to Choose Effectively
Chapter 6 spells out the implications of Cooperation Theory for anyone who is in a Prisoner’s Dilemma. From the participant’s point of view, the object is to do as well as possible, regardless of how well the other player does. Based upon the tournament results and the formal propositions, four simple suggestions are offered for individual choice:

  1. Do not be envious of the other player’s success;
  2. Do not be the first to defect;
  3. Reciprocate both cooperation and defection;
  4. Do not be too clever.

Understanding the perspective of a participant can also serve as the foundation for seeing what can be done to make it easier for cooperation to develop among egoists.

Chapter 7: How to Promote Cooperation
Chapter 7 takes the Olympian perspective of a reformer who wants to alter the very terms of the interactions so as to promote the emergence of cooperation. A wide variety of methods are considered, such as making the interactions between the players more durable and frequent, teaching the participants to care about each other, and teaching them to understand the value of reciprocity. This reformer’s perspective provides insights into a wide variety of topics, from the strength of bureaucracy to the difficulties of Gypsies, and from the morality of TIT FOR TAT to the art of writing treaties.

Here are author’s recommendations:

  1. Enlarge the shadow of the future
  2. Change the payoffs
  3. Teach people to care for each other
  4. Teach reciprocity
  5. Improve recognition abilities

V: Conclusions
Chapter 8: The Social Structure of Cooperation
Chapter 8 extends the implications of Cooperation Theory into new domains. It shows how different kinds of social structure affect the way cooperation can develop. For example, people often relate to each other in ways that are influenced by observable features, such as sex, age, skin color, and style of dress. These cues can lead to social structures based on stereotyping and status hierarchies. As another example of social structure, the role of reputation is considered. The struggle to establish and maintain one’s reputation can be a major feature of intense conflicts. For example, the American government’s escalation of the war in Vietnam in 1965 was mainly due to its desire to deter other challenges to its interests by maintaining its reputation on the world stage. This chapter also considers a government’s concern for maintaining its reputation with its own citizens. To be effective, a government cannot enforce any standards it chooses but must elicit compliance from a majority of the governed. To do this requires setting the rules so that most of the governed find it profitable to obey most of the time. The implications of this approach are fundamental to the operation of authority, and are illustrated by the regulation of industrial pollution and the supervision of divorce settlements.

Chapter 9: The Robustness of Reciprocity

By the final chapter, the discussion has developed from the study of the emergence of cooperation among egoists without central authority to an analysis of what happens when people actually do care about each other and what happens when there is central authority. But the basic approach is always the same: seeing how individuals operate in their own interest reveals what happens to the whole group. This approach allows more than the understanding of the perspective of a single player. It also provides an appreciation of what it takes to promote the stability of mutual cooperation in a given setting. The most promising finding is that if the facts of Cooperation Theory are known by participants with foresight, the evolution of cooperation can be speeded up.


This classical book confirms once again my believe that the only reasonable behavior in interacting with other people is TIT-FOR-TAT despite its negative connotation as “eye for an eye”. However, the default to initial cooperation removes this negativity as long as other player uses the same strategy. Generally, author’s examples from real life confirm this finding, but a couple of important issues remain unresolved. The most important is probably the case when reciprocity is not possible, for instance because of lack of resources to use for this. Another one is complexity of the world, when players interact via multiple intermediaries who apply variety of strategies and the traceability of TIT-FOR-TAT is all but impossible. However, it is still very usable to have robust results for optimal strategy, however limited is its application in real life.  

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