《政治经济学经典导读 Comparative Political Economy》课程教学资源（阅读资料）The Evolution of Cooperation

Introduction confronted with an iterated Prisoner's Dilemma.This ex- ploration 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 tourna- ments reveals four properties which tend to make a deci- sion 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,for- giveness 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 un- der suitable conditions,cooperation can indeed emerge in a world of egoists without central authority.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 nut- shell.The evolution of cooperation requires that individ- uals 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 20

Introduction confronted with an iterated Prisoner's Dilemma. This ex￾ploration 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 tourna￾ments reveals four properties which tend to make a deci￾sion 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, for￾giveness 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 un￾der suitable conditions, cooperation can indeed emerge in a world of egoists without central authority. 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 nut￾shell. The evolution of cooperation requires that individ￾uals 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. 20

The Problem ofCooperation 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 reci- procity and have even a small proportion of their interac- tions 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 estab- lished on the basis of reciprocity,can protect itself from invasion by less cooperative strategies.Thus,the gear wheels of social evolution have a ratchet. Chapters 4 and 5 take concrete settings to demonstrate just how widely these results apply.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 killprovided 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 oth- er for extended periods of time.The soldiers of these op- posing 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 coop- 21

The Problem of Cooperation 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 reci￾procity and have even a small proportion of their interac￾tions 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 estab￾lished on the basis of reciprocity, can protect itself from invasion by less cooperative strategies. Thus, the gear wheels of social evolution have a ratchet. Chapters 4 and 5 take concrete settings to demonstrate just how widely these results apply. 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 oth￾er for extended periods of time. The soldiers of these op￾posing 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 coop- 21

Introduction eration.Under suitable conditions,cooperation based upon reciprocity can develop even between antagonists. Chapter 5,written with evolutionary biologist William D.Hamilton,demonstrates that cooperation can emerge even without foresight.This is done by showing that Co- operation 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 be- havior.What makes this possible are the evolutionary mechanisms of genetics and survival of the fittest.An indi- vidual able to achieve a beneficial response from another is more likely to have offspring that survive and that contin- ue the pattern of behavior which elicited beneficial re- sponses from others.Thus,under suitable conditions,coop- eration 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 advan- tage 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 co- operation,it can certainly be helpful.Therefore chapters 6 and 7 are devoted to offering advice to participants and reformers,respectively.Chapter 6 spells out the implica- tions of Cooperation Theory for anyone who is in a Prison- er'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 22

Introduction eration. Under suitable conditions, cooperation based upon reciprocity can develop even between antagonists. Chapter 5, written with evolutionary biologist William D. Hamilton, demonstrates that cooperation can emerge even without foresight. This is done by showing that Co￾operation 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 be￾havior. What makes this possible are the evolutionary mechanisms of genetics and survival of the fittest. An indi￾vidual able to achieve a beneficial response from another is more likely to have offspring that survive and that contin￾ue the pattern of behavior which elicited beneficial re￾sponses from others. Thus, under suitable conditions, coop￾eration 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 advan￾tage 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 co￾operation, it can certainly be helpful. Therefore chapters 6 and 7 are devoted to offering advice to participants and reformers, respectively. Chapter 6 spells out the implica￾tions of Cooperation Theory for anyone who is in a Prison￾er'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 22

The Problem ofCooperation offered for individual choice:do not be envious of the oth- er player's success;do not be the first to defect;reciprocate both cooperation and defection;and 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. Thus,chapter 7 takes the Olympian perspective of a re- former who wants to alter the very terms of the interac- tions 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 fre- quent,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. Chapter 8 extends the implications of Cooperation The- ory 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 struc- tures based on stereotyping and status hierarchies.As an- other 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 reputa- tion on the world stage.This chapter also considers a gov- ernment's concern for maintaining its reputation with its own citizens.To be effective,a government cannot enforce 23

The Problem of Cooperation offered for individual choice: do not be envious of the oth￾er player's success; do not be the first to defect; reciprocate both cooperation and defection; and 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. Thus, chapter 7 takes the Olympian perspective of a re￾former who wants to alter the very terms of the interac￾tions 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 fre￾quent, 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. Chapter 8 extends the implications of Cooperation The￾ory 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 struc￾tures based on stereotyping and status hierarchies. As an￾other 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 reputa￾tion on the world stage. This chapter also considers a gov￾ernment's concern for maintaining its reputation with its own citizens. To be effective, a government cannot enforce 23

Introduction 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 ofauthority,and are illustrat- ed by the regulation of industrial pollution and the supervi- sion of divorce settlements. 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 ap- proach 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 co- operation can be speeded up. 24

Introduction 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 illustrat￾ed by the regulation of industrial pollution and the supervi￾sion of divorce settlements. 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 ap￾proach 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 co￾operation can be speeded up. 24