Approaching Micro-Macro Dynamics through Evolutionary Game ...

Approaching Micro-Macro Dynamics through Evolutionary Game ...

An evolutionary game approach to culture: Illustration by an adaptive norm development Tatsuya Kameda (Hokkaido University) [email protected] http://lynx.let.hokudai.ac.jp/members/kameda CEFOM/21, 2nd Workshop Culture, Norm, and Evolution Hokkaido University, Aug. 6-8, 2003 1 Overview Resurgence of collective constructs (e.g., norms, conventions, values) in social sciences How can we study these collective constructs fruitfully? Adaptive perspective Evolutionary game theory as a useful

research tool An illustration with communal-sharing norm in primordial societies 2 Social norm Cialdini & Trost (1998) Social norms are rules and standards that are understood by members of a group, and that guide and/or constrain so cial behavior without the force of laws. These norms emer ge out of interaction with others; they may or may not be st ated explicitly, and any sanctions for deviating from them c ome from social networks, not the legal system (p.152). Socially-shared rules that emerge and are sustain ed through people's autonomous interaction, not necessarily with formal regulating authorities or fo

rces such as laws 3 Theory of norm development? Emergence and sustainability of social norms as core issues for any theory of social norms. But, do we have a reasonable theory of norm de velopment in this sense? Classic studies on norm development (e.g., Sherif, 1936; Jacobs & Campbell, 1961): adaptively irrelevan t norms Social/cultural learning as a general engine for n orm development, but 4 Theory of norm development? A more fundamental question: Why some

beliefs are acquired socially and are maintained as a shared rule, while other beliefs are not. Adaptive/evolutionary perspective Beliefs that help us acquire a fit behavior in a given social/physical environment are more likely to be transmitted culturally and maintained as a social norm. 5 Illustration: Norms about foodsharing in primordial societies Kaplan & Hill (1985): Fieldwork on the Ache foragers in Paraguay Collected resources (vegetables, fruits) Kin-sharing Hunted game (peccary, monkey, deer) Communal-sharing including non-family

members widely Existence of two different sharing rules/norms in the same society: Why? 6 Why communal-sharing of hunted games? Risk-reduction hypothesis Acquisition of a meat is a highly variable, uncertain prospect, compared to the provision of collected resources. Communal-sharing system functions as a collective-risk reduction device. By including more individuals in the riskpooling group, the variance in food supply

decreases exponentially. 7 Intuitively appealing, but truly adaptive explanation? Problem of egoism in social sharing Hunted meat is often regarded as a common property or public goods in hunter-gather societies. What if egoists emerge in the group who just share

others acquisitions but are never willing to share his own acquisition? Emphasizing adaptive function of the whole system, but silent about how those egoists are precluded in the group. Need a theory based on individual-level adaptation rather than group-level adaptation. 8 A theory about development of the communal sharing norm Proposing a theory based on individual-level adaptation Using an evolutionary game analysis Maynard Smith (1982): Evolutionary biology

Axelrod (1984): Introduction to social sciences 9 Evolutionary game Represents various behavioral/cognitive properties of individuals as strategies in a game. Examines how each strategy performs in the game against other strategies in terms of net profit. More fit strategies proliferate in the population gradually (via social/cultural learning). Different from classical game theory, it does not assume players with super-intelligent information processing ability. 10 Applying the evolutionary game analysis to adaptive norm development

EGA: Does the interaction among given individu al behavioral/cognitive strategies lead to a stable collective state (evolutionary equilibrium) wher e the population is dominated by a single strateg y (or a set of strategies)? Social norm: a stable set of socially-shared beha vioral/cognitive properties (Cialdini & Trost, 199 8) EGA is particularly suited for examining adaptive norm developments in societies. 11 Our model: 4 behavioral strategies about sharing under uncertainty When in the non-acquirer role When in the acquirer

role Demanding communal-sharing Granting another acquirers ownership Provisioning as a common property Communal sharer Saint Claiming private ownership

Egoist Bourgeois 12 Key Question: Can communal sharers outperform other types of members in the population? Basic Model Acquirer with a resource of value V (e.g., hunted meat) Depending on behavioral strategies, some individuals may demand communal sharing of the resource. Refusal of the acquirer to share the resource leads to fights that may incur cost C to each loser.

13 Evolutionary computer simulations Implement the four behavioral strategies in a same population and let them interact. A strategy that achieves higher profit than the other strategies increase its proportion in the population gradually. Emergence of a stable equilibrium over time? 14 Results of a simulation starting with nearly 100% egoists in the population Stable Proportions in the group 1

0.9 0.8 0.7 0.6 0.5 0.4 0.3 Bourgeios Saint Egoist Communal Sharer 0.2 0.1 Evolvable from nearly zero 0

Generation 15 2nd-(and higher-) order free-riding? How can this issue be solved? 16 Communal sharers Lukewarm normenforcers (1st -order free riders) > Committed Enforcers Tolerant toward the

lukewarm members (2nd-order free riders) > Intolerant 17 However, the infinite regress is blocked. The lukewarm members (1st-order free rider) quickly acquir

e behavioral propensity to be less reactive (less likely to en gage in fighting when refused access to the resource) agai nst intolerant members (p2), than against non-sharers (p1). p1 > p2 Lukewarm members p1 is already small. Thus, p2 is negligi ble. That is, lukewarm members back off, when refused to access the resource by the intolerant members. So, no fitness differences accrue between the tolerant and the intolerant members. Tolerant members can survive, w hile effectively eliminating the lukewarm members. See Kameda, Takezawa & Hastie (2003) for details. 18 F r e q u e n c ie s o f d o n a t o r s Communal-sharing mind under uncertainty? 16

Certain Uncertain 14 12 10 8 6 4 2 0 0 100 200 300

400 500 600 700 750 The am ount of money donated (in yen) Conceptually parallel patterns were also obtained with Am erican samples (see Kameda, Takezawa, Tindale, & Smith, 2002) 19 Conclusion Communal-sharing ideology can develop to a stable equilibrium (-- socially-shared rule) under uncertainty, as a result of individual-level fitness maximization. Although living in modern societies (US and Japan), communal-sharing minds are triggered easily for uncertain resources. Such an operation of mind is adaptive under uncertainty. Evolutionary game analysis is a powerful research tool to understand various micro-macro

dynamics in our societies. 20 Some thought experiment: Two imaginary commentators Promising conclusion, but any limitations in the current communal-sharing model? Two imaginary commentators A behavioral ecologist A comparative institutional economist 21 Behavioral ecologist

An interesting talk. Methodologically sound and theoretically coherent with work in behavioral ecology. One critical question Given your model, why dont chimps (or other social animals) engage in communal sharing? They may have the same adaptive problem of uncertainty-reduction in food supply, but no primates other than humans have a broad food-sharing system. What elements in your model limit its scope just to humans? Some sophisticated cognitive mechanisms are assumed in your model? 22 A comparative institutional economist I

like your talk, but share the concern with the behavioral ecologist. Technological and ecological factors may not be the sole determinants in the selection of a (social) equilibrium; historical and social factors may also matter. Otherwise, norms are nothing but a mechanical transformation of technological and ecological characteristics (Aoki, 2001, p.50) 23 What do these (imaginary) criticisms imply? My model: Communal-sharing norm as evoked by the local ecological conditions

High variance (uncertainty) in meat supply Group-living: no privacy Behavioral ecologist: Chimps and other social animals may have the same local ecological condition. Then, why dont they have the communal-sharing norm? Do they lack sophisticated cognitive mechanisms? What exactly are these mechanisms? Comparative institutional economist: Just a mechanical transformation of ecological characteristics into a norm? Specific historical and social factors leading to the norm? Any role of beliefs?

24 Evoked culture vs. Epidemiological culture Tooby Evoked culture: Culture triggered by local circum stances; Shared local conditions lead to within-gr oup behavioral similarities and between-group be havioral differences. & Cosmides (1992) Local ecological conditions evoke culture. Epidemiological culture: Culture maintained by c onstructing shared representations.

Traditional conceptualization of culture (transmitted c ulture) in social sciences (e.g., Sperber, 1996) 25 (contd) Evolutionary psychologists tend to emphasize the role of evoked culture in human societies. However, in the evoked culture, cultural beliefs, in principle, do not play a unique, independent role from behavior. Beliefs are just psychological counterparts (reflections) of the adaptive behavior in the local environment, and might even be argued as a redundant concept. However, cultural beliefs matter!

Chimps vs. humans (re. cultural capacities) Social/historical changes 26 Challenges! So, real challenge is to go beyond the evoked culture and theoretically incorporate the epidemiological (transmitted) culture into the adaptive perspective. Cross-fertilization among different disciplines is essential.

Psychology Evolutionary anthropology Economics (comparative institutional analysis) Game-theoretic framework (including evolutionary and repeated game approaches) provides a common platform. 27 References

Aoki, M. (2001). Toward a comparative institutional analysis. MIT Press. Axelrod, R. (1986). An evolutionary approach to norms. American Political Science Review, 80, 10951111. Axerlod, R. (1984). The evolution of cooperation. Basic books. Boyd, R., & Richerson, P.J. (1985). Culture and the evolutionary process. U. Chicago Press. Boyd, R., & Richerson, P.J. (1996). Why culture is common, but cultural evolution is rare. Proceedings of the British Academy, 88, 77-93. Cialdini, R. B., & Trost, M. R. (1998). Social influence: Social norms, conformity, and compliance. In D. T. Gilbert, S. T. Fiske, & G. Lindzey (Eds.), The handbook of social psychology (4th ed., Vol. 2, pp. 151-192). McGraw-Hill. Foley, R. (1987). Another unique species: Patterns in human evolutionary ecology. Academic Press.

Kameda, T., & Nakanishi, D. (2002). Cost-benefit analysis of social/cultural learning in a non-stationary uncertain environment. Evolution and Human Behavior, 23, 373-393. Kameda, T., & Nakanishi, D. (2003). Does social/cultural learning increase human adaptability? Rogerss question revisited. Evolution and Human Behavior, 4, 242-260. Kameda, T., Takezawa, M., & Hastie, R. (2003). The logic of social sharing: An evolutionary game analysis of adaptive norm development. Personality and Social Psychology Review, 7, 2-19. Kameda, T., Takezawa, M., Tindale, R. S., & Smith, C. (2002). Social sharing and risk reduction: Exploring a computational algorithm for the psychology of windfall gains. Evolution and Human Behavior, 23, 11-33. Kaplan, H., & Hill, K. (1985). Food sharing among Ache foragers: Tests of explanatory hypotheses. Current Anthropology, 26, 223-246. Maynard Smith, J. (1982). Evolution and the theory of games. Cambridge U. Press. Sperbar, D. (1996). Explaining culture: A naturalistic approach. Blackwell. Tooby, J., & Cosmides, L. (1992). The psychological foundations of culture. In J.H.Barkow, L.Cosmides, & J.Tooby (Eds.), The adapted mind: Evolutionary psychology and the generation of mind (pp.19136). Oxford U. Press. 28 Yamagishi, T. (1986). The provision of a sanctioning system as a public good. Journal of Personality and Social Psychology, 50, 110-116.

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