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叶 航

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beyond “homo economicus ”  

2006-11-19 20:21:32|  分类: 默认分类 |  标签: |举报 |字号 订阅

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Economics based on hypothesis beyond

“Homo Economicus ”

 

Ye Hang 

I will start my lecture with a story that my friend told meOn a flight my friend took the other day, he watched the stewardess give the usual five minute safety presentation, and for the first time stopped to think about the implications of some of her words, which he had heard hundreds of times before without noticing them.

In the event the cabin depressurizes, oxygen masks will automatically drop from the ceiling. The stewardess warned us to make sure we put our own masks on before attempting to help our seatmates with theirs. This is part of an FAA-approved script, from which they never depart in making these presentations.

We imagine that this warning is aimed at the following scenario. The cabin depressurizes and anyone without a mask will become unconscious in moments. Your seatmates are children or otherwise helpless. If you attempt to help them without securing your own mask first, you will pass out without succeeding and everyone will die or become incapacitated. If you put your own mask on, your seatmates may pass out but will revive as soon as you have placed their masks on their faces. Thus, your attempt to help them will only succeed if you help yourself first.

It is marvellous to think that the danger of a human being assisting another before herself is so great that the FAA felt the need to warn against it on every airplane flight. The implication is that if the oxygen masks drop from the ceiling, it is human nature--immediate, instinctive behavior-- to assist your companions with their masks before you don yours. Such altruism in the face of danger reveals great compassion, for it is performed in a moment of terrible risk, at great potential cost to oneself, when no-one knows what the future holds.

Perhaps there is no subject like economics that cares so much about human cooperation. As we will find in this corpus that economists applied numerous mathematical tools(mainly game theory) to model for cooperative behavior, social experiment, computer simulation as well as functional magnetism resonation are also used to study this issue. As far as I’m concerned, it is not because that economists are more concerned about human fate than any other scientists but because that this issue poses serious threat to the modern main economic theory, which is Achille’s heel in the giant Economics. 

Economics doesn’t know whether it should thank or curse W. Tucker, a mathematician and professor in Princeton University. On a day in 1950, in order to explain a theory(i.e. the later-named Nash Theory enabled Nash to win the Nobel Prize in 1994) proposed by a student in a routine seminar, he wrote an example on the black board. The example is the world-famous “prisoner dilemma” 

Since more than half century passed,“prisoner dilemma” has gone beyond its “master” and won its independent academic status. One may not know or care about “Nash equilibrium” and its mathematical description behind this game, but he can't help thinking of the profound connotation contained in the example: if everyone makes decision by or only by rational principle, then what make human cooperation possible? What make human society exist? As Bowels and Gintis asked in “Solving the Puzzle of Prosociality”: Individuals often do better by coordinating and sharing the benefits of their activities rather than each acting alone. The benefit accruing to the group from each individual’s cooperation in such cases is greater than the cost to the individual, but nonetheless, each individual would be better off not incurring the cost of cooperation, and simply benefiting from the efforts of the other group members. If all participants follow self-interested logic, however, cooperation will fail. When it is maintained, cooperation is altruistic, in the sense of being group-beneficial but personally costly. Why are such altruistic behaviors not driven out by self-interested agents(see ‘Solving the Puzzle of Prosociality’)? 

Since the latter half of last century, a lot of literature on “prisoner dilemma” has surged. A plausible solution is to see one-shot “prisoner dilemma” as a subgame in the process of multi-repeated interactions, then human “rational” ability, including trial-and-error, learning and bargaining, will lead the partners of the game to cooperation. Nonetheless, even though we don’t care whether it’s reasonable to replace “one-shot game” with “repeated game” in argumentation, empirical evidence from experiments and social observations tends to deny the critical role of “rationality” must play in the process of human cooperation as the former economic theory has predicted. As Bowels and Gintis pointed out that ‘much of the experimental evidence about human behaviors contributing to cooperation comes from nonrepeated interactions, or from the final round of a repeated interaction. We do not think that subjects are unaware of the one-shot setting, or unable to leave their real-world experiences with repeated interactions at the laboratory door. Indeed, evidence is overwhelming that humans readily distinguish between repeated and nonrepeated interactions and adapt their behavior accordingly. Nonexperimental evidence is equally telling: common behaviors in warfare as in everyday life are not easily explained by the expectation of future reciprocation’(see ‘the origin of human cooperation’); ‘when a group was threatened with extinction or dispersal, say through war, pestilence, or famine, cooperation was most needed for survival. But since the probability that the group will dissolve increases sharply under such conditions, cooperation based on future reciprocation cannot be maintained. Thus, precisely when a group is most in need of prosocial behavior, cooperation based on repeated interactions will collapse. 

Such critical periods were probably common in the evolutionary history of Homo sapien’s(see ‘Solving the Puzzle of Prosociality’)

    However, the development of economics throughout the 20th century are more dependent on the core hypothesis of “rational agent”. So-called agent refers to the person who pursues utility or interest maximization. However, in “prisoner dilemma” this hypothesis are faced with a dilemma: if we take “rationality” as the sole principle of human behavior, then economics must give up its efficiency principle; if we stick to “efficiency” principle, then economics must admit, at least in such occasion as “prisoner dilemma”, that it is not “rationality” that leads human to cooperation. Indeed, no matter which choice economics makes, the traditional main economic theory based on neo-classical economics is actually faced with an “overthrowing” revolution. In fact it is also the reason why we endeavor to introduce the pioneering work done by Gintis and so forth belonging to Santafe school to Chinese readers. 

   In 1982, 46 students in the department of economics in Hongberg, Germany, participated in an experiment called “ultimatum game”, conducted by professor W. Guth. Professor Guth later summarized the experiment in his paper like this: it is clear that subjects decide their behavior based on fairness other than on interest-maximization.

   In the past twenty years, ultimatum game and its variations have become one of the most heated subjects of experimental economics. There are one than one hundred papers on this subject. If you search “ultimatum game” by google, 168000 pieces of related information will be found. In all the experiments, the cross-culture ultimatum game experiment done by Gintis and so forth in Santafe institute is most attractive. Because the subjects in the experiments conducted before Gintis’ have been university students and while there are cultural differences among student populations throughout the world, these differences are small compared to the range of all social and cultural environments. The experiment lasted about a decade, and 12 experienced field researchers, working in 12 countries on five continents, recruited subjects from 15 small-scale societies exhibiting a wide variety of economic and cultural conditions. Nonetheless, the experimental result is  “systematically deviating from the canonical model, even the groups with smallest offers have mean offers greater than 25 percent of stake size”(   ). This research result is fully embodied in the report of “in search of homo economicus: behavioral experiments in 15 small-scale societies”. As the report suggests : recent investigations have uncovered large, consistent deviations from the predictions of the text book representation of Homo economics(Alvin E. Roth et al., 1991; Ernst Fehr and Simon Gachter, 2000; Colin Camerer, 2001). One problem appears to lie in economists’ canonical assumption that individuals are entirely self-interested: in addition to their own material payoffs, many experimental subjects appear to care about fairness and reciprocity, are willing to change the distribution of material outcomes at personal cost, and are willing to reward those who act in a cooperative manner while punishing those who do no even when these action are costly to the individual (see“in search of homo economicus: behavioral experiments in 15 small-scale societies”). 

“Economists were at first astonished at this behavior. Why would people reject a positive amount of money? They suggested that perhaps players did not understand the game. But by changing the rules a bit, experimenters showed that this was not the case. For instance, if the game is changed so that the offer is generated by a computer (and the responder is told this fact), the rejection rate becomes very low, however small a share is offered to the responder (Blount 1995). Similarly, if the game is changed so that if the responder rejects the proposer’s offer, he receives zero payoff, but the proposer still receives the share he proposed for himself, responders almost never rejected offers” (see “Solving the Puzzle of Prosociality”).The experimental result clearly pro and con  tells us that at least in such occasion as ultimatum game people don't behave according to the hypothesis of “rational agent”. Interestingly enough, the denial of “rational agent” hypothesis not only comes from recipients “who refuse positive amount of money” but also from proposers “who give fair offer”. Although, the proposers in the experiment can still be regarded as “rational agent”, for we can’t exclude a possibility that the proposers predict that if they don’t give fair offer, they will face a high refusal rate. It is this “rational” judgment that discloses the false of “rational agent” hypothesis of main economic theory at a more profound level: for it shows that common knowledge of the partners of the game is based on “fairness” rather than on “interest” and that it is the acknowledgement of “fairness” that makes the proposers’ offers deviate from “Nash Equilibrium”. As we know that “common knowledge” is the premise of every game and also determines the players “strategy set”. If the common knowledge of human cooperation is “fairness” instead of “interest-maximization”, then to economics, the significance of “ultimatum game” differing from “prisoner’s dilemma” lie in the following: “prisoner’s dilemma discloses the internal contradiction of “rational agent” hypothesis form logic perspective, while “ultimatum game” shows the real possibility of a hypothesis beyond “rational agent” form empirical perspective.

  As we will find in the corpus that the endeavor Gintis and so forth in Santafe School has made is “revolutionary”: although they claim that they are “searching for rational agent”, they actually to some extent find agent beyond “rationality”; so they try to modify the premise of traditional economics according to new material, thus establishing economics beyond “rational agent”. 

   “Reciprocity” is the key word appearing in the corpus with high frequency, though we translate literally “互惠” or “互惠性”, however, the Chinese characters can’t cover the connotation of the original word. So it’s necessary for me to explain it in detail. First, “互惠” in Chinese means that if you are “kind” to (or cooperating with) me, and I’ll be kind to(or cooperating with) you; and vice versa. Obviously, “互惠”can’t cover the latter connotation. So Dingding suggest me to translate “reciprocity” into “对等(equivalence)”. Second, after going through the papers written by Gintis and so on, we’ll find that translating “reciprocity” into “对等(equivalence)” still can’t express the writers’ real intention, for in common context,

“equivalence” mainly refers to the relationship between the two players of the game; however, the behavior Gintis and so on wants to emphasis is: if you are kind to people(here people specially refer to me and any others), then I will be kind to you; if you are “unkind” to others, though you still be kind to me, then I will be “unkind” to you and punish you; here Gintis put emphasis on “third party” (i.e. interest-free) supervision and punishment; “equivalence” can’t cover this connotation. Third, according to my own understanding, as the writer has emphasized that the profound connotation of “reciprocity” lies in as follows: “reciprocity” refers to a predisposition to punish the third party, though it has nothing to do with me, I still want to punish “bad” guys at my personal cost to “punish the bad guys and carry forward the kindness”. In a sense, we call it “sense of justice”. From the papers of Gintis we know it is the altruistic and prosocial emotions and behaviors that makes human cooperation possible and that we can fully realize that “self-interested rational agent” hypothesis of the traditional economics can’t include the motivation of human behaviors and behavioral mechanism behind this motivation. “science” magazine, published in Aug, 2004, contains a cover article “ the Neural Basis of Altruistic Punishment”, written by Austrian scholar Ernst Fehr et al., who have close relationship with Santafe School. This article is an important literature which uses modern scientific means to explain and test Gintis’ the origin of human cooperation and evolution hypothesis. (see  ). In this article, Professor Fehr directly refers “reciprocity” to “altruistic punishment” 

We think that cooperation and the surplus brought about by cooperation may be the ultimate reason why human being’s intelligence as well as human behaviors co-evolved with human culture and institutions. In the evolutionary link of millions of years, the initial motivation of evolution originated from selection pressure of the nature itself, that is, nature’s selection pressure forced human evolution to be favored with cooperation. As this process was carried on by natural forces, we call the period “ nature setting law for human being”. With the improvement of human productivity, the selection pressure on human imposed by nature began to diminish and cooperative order couldn’t maintain by merely self-constraint, then human entered the age of what Gintis and Bowels described, which is called a hunter-gather society about 100,000 years ago. The computer simulation strictly designed on anthropological knowledge reveals that the altruistic punishment enforced by strong reciprocators is a “evolutionarily stable strategy”, which will sustain human cooperation on a larger scale and hence significantly raise the survival opportunity for the group. In this period, the internalized social norms still played a role, however, altruistic punishment enforced by strong reciprocators had an insubstituting role in maintaining the cooperative order, therefore, we call this period “individual setting law for society”. Finally, in contemporary and modern society, especially the unprecedented division of labor brought about by Industrial Revolution made human cooperation change fundamentally on its scale and in its degree. The cooperation must depend on ever improving judicature established upon rationality and democracy, therefore, we call this period “ society setting law for individual”.

We infer that in order to maintain cooperative order, the successfully evolved prosocial emotions as sympathy, guilt, shame, remorse,gratitude and justice(strong reciprocators or altruistic punishment),in the early stage of human being is the key to understanding human’s pure altruistic behaviors; pure altruistic behaviors can’t get compensation from outside as kin altruism, reciprocal altruism and self-interested behaviors do, so they must depend on a stimulating- trigger mechanism which enables the behavior to get satisfaction form the behavior itself, the cover article in Science of August,2004 is the research report of Fehr et al.,in Zurich University, which reports their observation of neural basis of “altruistic punishment” by positron emission tomography in great detail. The research shows that the brain areas that the altruistic punishment activates are midbrain system dominating human’s emotions. Gintis and Bowels in Santa Fe Institute just published a sensational paper in Theoretical biology magazine, which reported their result of computer simulations. The results show that in the early period of human evolution, altruistic punishment which was regarded as human prosocial emotions and internalized norms is a decisive factor for group members to maintain cooperation.

 

 

 

 

 

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