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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 – – – 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: – – – – – polarization of opinion riots & revolutions panics emergence of norms market crashes – – – – – 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 – – 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