清华大学博弈论2

如何考虑策略博弈 How to Think About Strategic Games第2章 Chapter 2

内容提要 Outline决策与博弈 Decisions versus games博弈分类 Classifying games术语与基本假设 Some terminology and background assumptions

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决策与博弈 Decisions Versus Games博弈，或策略博弈：有意识的参与者之间的相互作用。(因此博弈又译作对策互作用 (因此“博弈”又译作“对策”。) ) Games, or Strategic games: Interactions between mutually aware players players.决策:一个人的选择不必考虑其他人的反应。 Decisions: Action situations where each person can choose without concern for reaction or response from others.Slide 3

决策与博弈 Decisions Versus Games策略博弈在两三个参与者的面对面的对抗中经常出现。 Strategic games arise most prominently in headto-head confrontations of two (or a few) participants.相反，大量参与者之间的相互作用看起来就不太象策略博相反大量参与者之间的相互作用看起来就不太象策略博弈。 In contrast, interactions among a large number of participants seem less prone to strategic games. games不过，许多场合起初看起来象是有成千上万参与人的“非人格化的市场后来变成两人间策略性的相作用人格化的”市场，后来变成两三人之间策略性的相互作用。 However, many situations that start out as impersonal markets with thousands of participants turn into strategic interactions of two or a few.Slide 4

博弈分类 Classifying Games序贯博弈和同时博弈 Are the moves in the game sequential or simultaneous?利益冲突和利益相容 Are the players’ interests in total conflict or is there some commonality? y一次博弈和重复博弈 Is the game p y g played once or repeatedly, p y, and with the same or changing opponents?Slide 5

博弈分类(续) Classifying Games完全(对等)信息或不完全信息 Do the players have full or equal information?规则固定或可操纵 Are the rules of game fixed or i l bl? manipulable?合作协议是否具有强制性 Are agreements to cooperate enforceable?Slide 6

分类方法1:序贯博弈和同时博弈 Are the Moves in the Game Sequential or Simultaneous?如果博弈的规则规定了一个严格的顺序，每一行动时刻只允许个参与者采取行动，而且他知道自己和其刻只允许一个参与者采取行动，而且他知道自己和其他人过去所采取的行动，则博弈中的出招是顺序的。 The moves in a game are sequential if the rules of the game specify a strict order such that at each action moment only one player takes action with knowledge of the actions taken action, (by others and himself) at previous moments.

例：下棋 E g Moves in Chess E.g.,

我们用“树”来分析这样的博弈。 We use“trees” as tools to analyze such games. y gSlide 7

分类方法1:序贯博

弈和同时博弈 Are the Moves in the Game Sequential or Simultaneous?在序贯博弈中，你当前的出招是依据你对未来后果的算计。后果的算计 In a sequential-move game, your current move is governed by your calculation of its future consequences.对序贯博弈的研究告诉我们什么时候有先发优势、什么时候有后发优势。 The t d f Th study of sequential games tells us ti l t ll when it is advantage to move first and when second. h dSlide 8

分类方法1:序贯博弈和同时博弈 Are the Moves in the Game Sequential or Simultaneous?如果每个参与者必须在(完全)不知道其他人的选择下采取行动，那么这个博弈中的出招是的选择下采取行动那么这个博弈中的出招是同时的。 The moves in a game are simultaneous g if each player must take his action without knowledge of the choices of others.

例：密封式拍卖 E.g., sealed-bid auctions

我们使用“表”来分析这样的博弈。 We use“tables” to analyze such games.Slide 9

分类方法1:序贯博弈和同时博弈 Are the Moves in the Game Sequential or Simultaneous?在同时博弈中，你的一个玄妙的任务是试图找出对手现在要做的事情现在要做的事情。 With simultaneous moves, you have the trickier task of trying to figure out what your opponent is going to do right now.

与此同时，对手也在试图找出你的当前行动。 At the same time, the opponent is also trying to fig e out your current move. ent mo e figure o t o c而且，你必须认识到对手在做这件事；你的对手也必须认识到……以此类推。 And, A d you must recognize your opponent is trying to t i ti t i t figure out your current move while your opponent must recognize……and so on.Slide 10

分类方法2:利益冲突和利益相容 Are the Players Interests in Total Conflict Players’ or Is There Some Commonality?某些博弈中，一人所得即为他人所失。 In some games, one player s gain is the player’s other’s loss.参与者的利益完全冲突，这就好比他们在分割一个数量固定的收益。 The players’ interests are in complete p y p conflict when they are dividing up any fixed amount of possible gain.这样的博弈就是零和(或常和)博弈。 These games are zero-sum or constantsum games.Slide 11

分类方法2:利益冲突和利益相容 Are the Players Interests in Total Conflict Players’ or Is There Some Commonality?许多经济和社会博弈都不是零和的，但利益也不是完全一致的。不是完全一致的 Most economic and social games are not zero-sum, zero sum but the interests are not completely aligned either.许多现实中的博弈存在对抗和合作之间的张力许多现实中的博弈存在对抗和合作之间的张力。 Most games in reality have the tension between conflict and cooperation. b t fli t d ti

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分类方法2:利益冲

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