An Evolutionary Approach to Norms Author(s): Robert Axelrod Source: The American Political Science Review, Vol. 80, No. 4 (Dec., 1986), pp. 1095-1111 Published by: American Political Science Association Stable URL: http://www.jstor.org/stable/1960858 Accessed: 14/10/2009 09:23 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=apsa. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. American Political Science Association is collaborating with JSTOR to digitize, preserve and extend access to The American Political Science Review. http://www.jstor.org AN EVOLUTIONARY APPROACH TO NORMS ROBERT AXELROD Universityof Michigan Iorms providea powerfulmechanism for regulatingconflict in groups, even when there are more than two people and no central authority. This paper investigatesthe emergenceand stability of behavioralnorms in the context of a game played by people of limitedrationality. The dynamicsof this new normsgame are analyzedwith a computersimulation based upon the evolutionaryprinciple that strate- gies shown to be relatively effective will be used more in the future than less effective strategies. The results show the conditions under which norms can evolve and prove stable. One interestingpossibility is the employmentof metanorms,the willingness to punishsomeone who did not enforcea norm. Many historicalexamples of domesticand internationalnorms are used to illustrate the wide variety of mechanisms that can support norms, including metanorms, dominance, internalization,deterrence, social proof, membershipin groups, law, and reputation. An established support of dueling caused Hamilton to norm can have tremendouspower. This is risk, and ultimately to lose, his life-a illustratedby a historical instance of the powerful norm indeed, and yet one that norm of dueling.In 1804 Aaron Burrchal- has all but disappearedtoday after cen- lenged Alexander Hamilton to a duel. turies of power over life and death. Hamilton sat down the night before the Today, norms still govern much of our duel was to take place and wrote down his political and social lives. In politics, civil thoughts. He gave five reasons against rights and civil libertiesare as much pro- accepting the duel: his principles were tected by informal norms for what is against sheddingblood in a private com- acceptable as they are by the powers of bat forbiddenby law; he had a wife and the formal legal system. Leadership is children; he felt a sense of obligation itself subject to the power of norms, as towardhis creditors;he bore no ill against Nixon learned when he violated political Colonel Burr;and he would hazardmuch norms in trying to cover up Watergate. and could gain little. Moreover, he was The operation of Congress is shaped by reluctantto set a bad exampleby accept- many norms, including those governing ing a duel. Yet he did accept, because"the reciprocity(Matthews, 1960) and appren- ability to be useful, whether in resisting ticeship (Krehbiel, 1985). Across many mischiefor effectinggood, in those crises nations, tolerance of opposition is a of our public affairswhich seem likely to fragile norm that has great impact on happen, would probably be inseparable whether a democracy can survive in a from a conformity with public prejudice given country (Almond and Verba, 1963; in this particular"(Truman, 1884, pp. Dahl, 1966). In international political 345-48). In other words, the prospect of economy, norms are essential for the sanctionsimposed by the generalpublic in understandingof the operations of many AMERICAN POLITICAL SCIENCE REVIEW VOL. 80 NO. 4 DECEMBER, 1986 American Political Science Review Vol. 80 functionaldomains such as banking, oil, example,after many centuriesof colonial- and foreign aid (Axelrod and Keohane, ism, the intolerance of colonial depen- 1985; Keohane, 1984; Krasner, 1983). dence took hold in the relatively short Even in the domain of power politics, period of just two decades after World norms have virtually wiped out colonial- War II. Beforeand after such a transition, ism, inhibited the use of chemical war- the state of affairs seems very stable and fare, and retarded the spread of nuclear perhapseven permanent.For this reason, weapons. awarenessof a given norm is most intense Not only are norms important for precisely when it is being challenged. many central issues in political science, Examples of norms being challenged but they are vital to the other social today includethe right to smoke in public sciencesas well. Sociology seeks to under- without asking permission, the use of stand how different societies work, and gender-ladenlanguage, and the prohibi- clearlynorms are importantin these proc- tion against the use of chemicalwarfare. esses (e.g., Opp, 1979, 1983). Anthropol- Some of these challenges will succeed in ogy frequently deals with the unique establishing new norms, and some will featuresof various peoples by describing fail altogether. Thus, what is needed is in great detail their practicesand values, a theory that accounts not only for as in the case of feuding (e.g., Black- the norms existing at any point in time, Michaud, 1975). Psychologists are con- but also for how norms change over time. cerned with how people influence each To clarify these processes, one must first other and the manner in which an be clear about exactly what is being individualbecomes socializedinto a com- discussed. munity (e.g., Darley and Batson, 1973; In this next section the evolutionary Sherif, 1936). Economists are becoming approach to be used in this paper is interestedin the origin and operation of explained. Following this, the results of norms as they have come to realize that computersimulations of the evolution of markets involve a great deal of behavior norms are presented.The computersimu- based on standardsthat no one individual lations are then extended to include a can determinealone (e.g., Furubotnand specificmechanism for the enforcementof Pejovich, 1974; Schotter, 1981). norms, called metanorms. After these for- Largenumbers of individualsand even mal models are investigated,a wide vari- nations often display a great degree of ety of processesthat might help to sustain coordinatedbehavior that serves to regu- norms are discussed, along with sugges- late conflict. When this coordinated tions about how they too can be modeled. behavior takes place without the inter- The question of the origin and content of vention of a centralauthority to police the norms is considered, and finally, a sum- behavior, we tend to attribute the coor- mary and conclusionpresents the findings dinatedbehavior and the resultingregula- of this paperin the broad context of social tion of conflict to the existence of norms. and political change. To make this appeal to norms a useful explanation, we need a good theory of norms. Such a theory should help explain The EvolutionaryApproach threethings: how norms arise, how norms are maintained, and how one norm dis- Norms have been defined in various places another. ways in the differentliteratures and even One of the most importantfeatures of within the same literature.The threemost norms is that the standing of a norm can common types of definitions are based change in a surprisinglyshort time. For upon expectations,values, and behavior. 1096 1986 Evolution of Norms That these different definitions are used problems of defining credible threatsand for the same conceptreflects how expecta- of showing the consequencesof requiring tions, values, and behavior are often actors' expectations about each other to closely linked. Definitions based upon be consistentwith the experiencethat will expectations or values are favored by be generated by the resulting actions those who study norms as they exist in a (Abreu, Pearce, and Stacchetti, 1985; given social setting. Such definitions are Friedman,1971; Krepsand Wilson, 1982; convenient because interviews can elicit Selten, 1975). the beliefs and values of the participants, While deductions about what fully whereas systematically observing their rational actors will do are valuable for actual behavior is more difficult. Because their own sake, empirical examples of for many purposes the most important changing norms suggest that real people thing is actual behavior, a behavioral are more likely to use trial and error definitionwill be used in this study. behavior than detailed calculationsbased on accurate beliefs about the future. DEFINITION.A norm exists in a given Therefore,I have chosen not to study the social setting to the extent that indi- dynamics of norms using an