Download Consequentialist Models

The Rich Get Richer:
Self-Organizing Inequality and Agent-Based Modeling
Michael W. Macy
Cornell University
CSSI Workshop, Tohoku University
June 13, 2005
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….1
flocking behavior
 flock remains cohesive despite disturbances
 changes direction to avoid obstacles or
pursue a moving target
 appears to be organized by a leader – but
there is none!
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….2
flocking as group process
 flock behavior is highly complex
 but individual behavior is extremely simple:
– separation: avoid collisions
– alignment: match the vectors of neighbors
– cohesion: move toward the center of neighborhood
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….3
implications for social science
 individual human beings and social systems are
both extremely complex
 but flocking demonstrates that complexity of
social systems need not be based on complex
behavior.
 question: can we discover simple rules of local
interaction to explain persistent puzzles of social
life, including the reproduction of inequality?
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….4
how do you make a paperclip chain?
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….5
step one:
buy a nice big box of paperclips
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….6
step two:
open up the box and pour out the clips
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….7
step three:
spread the clips out on the table
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….8
step four:
find a chain and pick it up!
so where did the chain come from?
 Aquinas: God made it
– organization is evidence that there must be an
Organizer
– organization is imposed from the top down
 Descartes: (Discourse on Method, pt.V)
– God has better things to do than make paperclip
chains.
– instead God created the Universe as a self-organizing
system and turned it loose
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….10
most sociologists are Cartesians
 but many still assume inequality is imposed
from above…
–
–
–
–
–
elite theory
theory of the state
class, racial, or patriarchal domination
hegemonic ideology
theories of occupational or class closure, glass
ceilings, etc.
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….11
what if inequality is like a chain of
paperclips?
what can birds and paperclips tell us
about human behavior?
 birds have “bird brains”
 paperclips have no brains at all
 but flocks and chains have emergent properties!
– simple rules of local interaction
– generate complex global patterns
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….13
self-organizing group dynamics
 more like improvisational jazz than a
symphony orchestra
– people compose their “parts” on the fly, but not
just as they please
– but improvisation is badly behaved, highly
nonlinear
 requires a new approach to modeling
– old social science: interactions among variables
– new science of ABC modeling: interactions
among agents
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….14
what is self-organization?
 entropy: tendency toward disorganization
 self-organization:
– transfer of entropy to the environment
– hence, only in open systems, with permeable
boundaries
– characterizes the out-of-equilibrium dynamics of
autopoietic systems.
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….15
an autofactory is not autopoietic
(it is allopoietic)
reorganizes raw
materials and
energy into
autos which then
exit the system.
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….16
autopoietic system
Jupiter’s Great Red Spot is a vortex that has persisted for a much
longer time than the average amount of time any one-gas molecule
has spent within it.
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….17
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….18
examples of self-organization
natural systems
social systems
 hurricanes/tornados
 flocks, swarms, schools,
hives
 consciousness
 evolution
 life





traffic jams
high school cliques
residential segregation
social division of labor
reproduction of classes,
gender roles, etc.?
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….19
social self-organization
 actors are
– autonomous (behavior is internally generated)
– interdependent
 influence one another in response to influence they receive
 consequences of actions depend on actions of others
– embedded (local interaction)
 emergent patterns are dynamically stable
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….20
mechanisms for self-organizing inequality
 assortative mating, homophily, mobility
– Schelling neighborhood segregation
– but with people constantly moving in and out
– shifting boundaries (like Jupiter’s Great Red Spot)
 stable hierarchies
– status expectations, labeling,
– leveled aspirations
 gender differences that are dynamically stable
– Brinton: differential parental investment in Japan
– Ridgeway: self-reinforcing status characteristics
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….21
what is a “social agent”?
 cognitive architecture
– heuristic (norms, habits, rituals, routines, etc.)
– adaptive (learning, evolution)
 social architecture
– autonomous (self-organizing)
– interdependent
– relational (embedded in networks)
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….22
heuristic adaptive autonomous interdependent relational


“human beings viewed as behaving systems,
are quite simple” (Simon 1998)
behavior based on “rules of thumb” (norms,
conventions, rituals, routines, moral and social habits)
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….23
heuristic

population learning alters frequency distribution
across individuals
–
–
–

adaptive autonomous interdependent relational
evolutionary selection (survival and reproduction)
imitation (role modeling, conformity)
social influence (instruction, persuasion, suggestion)
individual learning alters probability distribution
within individuals
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–
–
reinforcement (behavioral propensities, attitudes)
bayesian updating (beliefs)
back-propagation of error in artificial neural networks
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….24
heuristic adaptive
autonomous interdependent relational
like self-organizing flocks and paperclip chains,
global patterns emerge spontaneously out of local
interaction
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….25
heuristic adaptive autonomous


interdependent relational
behavioral interdependence: agents influence
others in response to the influence that they
receive (persuasion, sanctioning, and imitation)
strategic interdependence: the consequences of
each agent’s decisions depend in part on the
choices of others (as in the prisoner’s dilemma)
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….26
heuristic adaptive autonomous interdependent

relational
group dynamics depend on network
properties
–
–
–
–
density
clustering (short cycles)
hubs, bridge ties (“small worlds”)
elective ties (dynamic networks)
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….27
applications of ABC models
 local interactions generate familiar but enigmatic global
patterns that may appear unexpected and then just as
dramatically disappear:
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–
–
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polarization of opinion
riots & revolutions
panics
emergence of norms
market crashes
–
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ethnic segregation & conflict
collective behavior
collapse of social trust
fads
feeding frenzies
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….28
Schelling’s Tipping Model
 an interesting and important puzzle:
– after 1964 housing discrimination was illegal
– since 1950 racial prejudice has declined
– yet neighborhoods remain highly segregated
 Schelling hypothesized that segregation:
– does not need to be imposed (top-down)
– does not reflect preferences (bottom-up)
– self-organizes through dynamic interaction
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….29
an agent
based
model of
the
emperor’s
new clothes
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….30
naked emperor’s are easy to find…

feigned allegiance
–
–
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adulation of an incoherent scholar
enthusiasm for a despised regime
peer pressure for self-destructive behaviors
–
–

drug or alcohol consumption (to be “cool”)
Kuran: Indian caste system
witch hunts
–
–

exposing “collaborators” to avoid exposure
homophobic violence to affirm masculinity
common theme: self-organizing status inequality
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….31
easy to find but hard to explain
 easy to explain why people succumb to peer
pressure.
 but why do they put public pressure on others to
comply with norms they privately oppose?
 to find out, we modeled the Andersen fable using
adaptive agents who influence one another in
response to the influence they receive.
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….32
a formal model of the Andersen fable
 agents make two decisions:
– whether or not to admire the Emperor
(“compliance”)
– whether to pressure others to do so as well
(“enforcement”)
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….33
how agents decide to comply
 “true believers” comply out of conviction
 “posers” comply if local pressure exceeds
conviction
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….34
why agents enforce
 “true believers” enforce their convictions
 “posers”
– fear exposure as approval-seeking imposters
– use enforcement to signal sincerity of convictions
 fanaticism of the new recruit to prove conviction
 “closet” deviants who persecute others to avoid
suspicion
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….35
what do we learn?
 parochial populations are highly vulnerable
 very unlikely in networks characteristic of
pluralistic societies
 the key people in these cascades:
– not those who are highly influential
 they start the cascade but do not sustain it
 critical role is played by those who are easily influenced!
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….36
why not use game theory instead?
 striking similarities
– global properties emerge from local interaction
– among strategically interdependent but autonomous
actors
 compared to natural language
– both are less nuanced
– but more rigorous
 an explicit logical structure whose validity can be tested
unequivocally
 ABC models are as rigorous as axiomatic theory
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….37
mathematical tractability imposes
limitations
 discourages complex or dynamic networks
– either a complete graph (hence a small N)
– or a random graph (no clustering, no hubs)
 applies to games played by game theorists
– perfect rationality
– complete information
– unlimited calculating ability
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….38
complexity from simple behaviors
 analytical and game theoretic models
– heroic assumptions about cognitive capacities
– social order is simplified as an equilibrium
 agent-based models reverse this.
– Agents follow simple rules that evolve through
experience
 observational and reinforcement learning
 imitation of “role models”
 competitive selection pressures
– population dynamics are highly complex
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….39
advantages of agent modeling
 identification of equilibrium says nothing about
–
–
–
–
probability that each equilibrium will obtain
path into or out of equilibrium
system behavior far from equilibrium
“Emperor’s New Clothes”
 unpopular norms are a global equilibrium
 but can agents get there from a random start?
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….40
a final thought to take home …
 is “self-organizing inequality” blaming the
victim?
 is it fatalistic?
 by identifying the mechanisms that underlie
emergent hierarchies, can we discover how to
make vicious circles turn virtuous?
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….41
END
The Rich Get Richer::Self-Organizing Inequality and Agent-Based Modeling………..…CSSI Workshop .…. June 13, 2005….42