An evolutionary game approach to culture: Illustration by an adaptive norm development

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An evolutionary game approach to culture
Illustration by an adaptive norm development

• Tatsuya Kameda (Hokkaido University)
• tkameda_at_let.hokudai.ac.jp
• http//lynx.let.hokudai.ac.jp/members/kameda

CEFOM/21, 2nd Workshop Culture, Norm, and
Evolution Hokkaido University, Aug. 6-8, 2003
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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

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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 social behavior without the
  force of laws. These norms emerge out of
  interaction with others they may or may not be
  stated explicitly, and any sanctions for
  deviating from them come from social networks,
  not the legal system (p.152).
• Socially-shared rules that emerge and are
  sustained through people's autonomous
  interaction, not necessarily with formal
  regulating authorities or forces such as laws

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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
  development in this sense?
• Classic studies on norm development (e.g.,
  Sherif, 1936 Jacobs Campbell, 1961)
  adaptively irrelevant norms
• Social/cultural learning as a general engine for
  norm development, but

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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.

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Illustration Norms about food-sharing 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?

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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 risk-pooling
  group, the variance in food supply decreases
  exponentially.

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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.

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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

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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.

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Applying the evolutionary game analysis to
adaptive norm development

• EGA Does the interaction among given individual
  behavioral/cognitive strategies lead to a stable
  collective state (evolutionary equilibrium)
  where the population is dominated by a single
  strategy (or a set of strategies)?
• Social norm a stable set of socially-shared
  behavioral/cognitive properties (Cialdini
  Trost, 1998)
• EGA is particularly suited for examining adaptive
  norm developments in societies.

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Our model 4 behavioral strategies about sharing
under uncertainty
        When in the non-acquirer role When in the non-acquirer role
        Demanding communal-sharing Granting another acquirers ownership
When in the acquirer role Provisioning as a common property Communal sharer Saint
When in the acquirer role Claiming private ownership Egoist Bourgeois
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Key Question Can communal sharers outperform
other types of members inthe population?
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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?

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Results of a simulation starting with nearly 100
egoists in the population
Stable
Evolvable from nearly zero
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• 2nd-(and higher-) order free-riding? How can
  this issue be solved?

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Communal sharers    
gt
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• However, the infinite regress is blocked.
• The lukewarm members (1st-order free rider)
  quickly acquire behavioral propensity to be less
  reactive (less likely to engage in fighting when
  refused access to the resource) against
  intolerant members (p2), than against non-sharers
  (p1). p1 gt p2
• Lukewarm members p1 is already small. Thus, p2
  is negligible. 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, while effectively
  eliminating the lukewarm members.
• See Kameda, Takezawa Hastie (2003) for details.

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Communal-sharing mind under uncertainty?
Conceptually parallel patterns were also obtained
with American samples (see Kameda, Takezawa,
Tindale, Smith, 2002)
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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.

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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

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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?

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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)

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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?

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Evoked culture vs. Epidemiological culture

• Tooby Cosmides (1992)
• Evoked culture Culture triggered by local
  circumstances Shared local conditions lead to
  within-group behavioral similarities and
  between-group behavioral differences.
• Local ecological conditions evoke culture.
• Epidemiological culture Culture maintained by
  constructing shared representations.
• Traditional conceptualization of culture
  (transmitted culture) in social sciences (e.g.,
  Sperber, 1996)

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(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

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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.

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References

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• Axelrod, R. (1986). An evolutionary approach to
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