Agent Zero: Toward Neurocognitive Foundations for Generative Social Science (Princeton Studies in Complexity) - Hardcover

Epstein, Joshua M.

Hardcover

ISBN 10: 0691158886 ISBN 13: 9780691158884

Verlag: Princeton University Press, 2014

Inhaltsangabe

The Final Volume of the Groundbreaking Trilogy on Agent-Based Modeling

In this pioneering synthesis, Joshua Epstein introduces a new theoretical entity: Agent_Zero. This software individual, or "agent," is endowed with distinct emotional/affective, cognitive/deliberative, and social modules. Grounded in contemporary neuroscience, these internal components interact to generate observed, often far-from-rational, individual behavior. When multiple agents of this new type move and interact spatially, they collectively generate an astonishing range of dynamics spanning the fields of social conflict, psychology, public health, law, network science, and economics.

Epstein weaves a computational tapestry with threads from Plato, Hume, Darwin, Pavlov, Smith, Tolstoy, Marx, James, and Dostoevsky, among others. This transformative synthesis of social philosophy, cognitive neuroscience, and agent-based modeling will fascinate scholars and students of every stripe. Epstein's computer programs are provided in the book or on its Princeton University Press website, along with movies of his "computational parables.?

Agent_Zero is a signal departure in what it includes (e.g., a new synthesis of neurally grounded internal modules), what it eschews (e.g., standard behavioral imitation), the phenomena it generates (from genocide to financial panic), and the modeling arsenal it offers the scientific community.

For generative social science, Agent_Zero presents a groundbreaking vision and the tools to realize it.

Über diesen Titel

Über die Autorin bzw. den Autor

Joshua M. Epstein directs the Center for Advanced Modeling at The Johns Hopkins University, where he is a professor in the Department of Emergency Medicine with joint appointments in the Departments of Applied Mathematics, Economics, International Health, Environmental Health Sciences, Biostatistics, Civil Engineering, and the Institute for Computational Medicine. He is also an external professor at the Santa Fe Institute. This volume forms a trilogy on agent-based modeling, with Growing Artificial Societies: Social Science from the Bottom Up (MIT), with coauthor Robert Axtell, and Generative Social Science: Studies in Agent-Based Computational Modeling (Princeton).

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"Agent Zero offers a solution to some of social science's great puzzles. Its behavioral basis is the interplay of emotion, cognition, and network contagion effects. It elegantly explains why so many human actions are so manifestly dysfunctional, and why some are downright evil."--George Akerlof, Nobel Laureate in Economics

"Rarely has a book stimulated me intellectually as much as this one. Particularly exciting is the incorporation of agents who feel (affect) and deliberate, as well as influence one another through social interaction. Epstein is a brilliantly creative scholar and the range of applications showcased here is stunning. In sum, this is a pathbreaking book."--Paul Slovic, University of Oregon

"Joshua Epstein proposes a parsimonious but powerful model of individual behavior that can generate an extraordinary range of group behaviors, including mob violence, manias and financial panics, rebellions, network dynamics, and a host of other complex social phenomena. This is a highly original, beautifully conceived, and important book."--Peyton Young, University of Oxford

"In social science generally and most notably in economics, the rational actor model has long been the benchmark for policy analysis and institutional design. Epstein now offers a worthy alternative:Agent_Zero, a mathematically and computationally tractable agent whose inner workings are grounded in neuroscience. Much like you and me,Agent_Zero is influenced by emotion, reason, and social pressures. Epstein demonstrates that collections of Agent Zeros perform amazingly like real groups, teams, and societies and can therefore serve as the fundamental building blocks for what he calls Generative Social Science. The rational actor now has a true competitor. Agent_Zero is a major advance."--Scott Page, University of Michigan

"This is social science based on how our brains actually work. Epstein's computerized 'agents' can feel passion and fear, and can influence each other emotionally. And when they interact, we see many of the realities of social life, from the dynamics of juries to racist violence to Arab springs. A remarkable and original piece of work."--W. Brian Arthur, Santa Fe Institute

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"Agent Zero offers a solution to some of social science's great puzzles. Its behavioral basis is the interplay of emotion, cognition, and network contagion effects. It elegantly explains why so many human actions are so manifestly dysfunctional, and why some are downright evil."--George Akerlof, Nobel Laureate in Economics

"Rarely has a book stimulated me intellectually as much as this one. Particularly exciting is the incorporation of agents who feel (affect) and deliberate, as well as influence one another through social interaction. Epstein is a brilliantly creative scholar and the range of applications showcased here is stunning. In sum, this is a pathbreaking book."--Paul Slovic, University of Oregon

"Joshua Epstein proposes a parsimonious but powerful model of individual behavior that can generate an extraordinary range of group behaviors, including mob violence, manias and financial panics, rebellions, network dynamics, and a host of other complex social phenomena. This is a highly original, beautifully conceived, and important book."--Peyton Young, University of Oxford

"In social science generally and most notably in economics, the rational actor model has long been the benchmark for policy analysis and institutional design. Epstein now offers a worthy alternative:Agent_Zero, a mathematically and computationally tractable agent whose inner workings are grounded in neuroscience. Much like you and me,Agent_Zero is influenced by emotion, reason, and social pressures. Epstein demonstrates that collections of Agent Zeros perform amazingly like real groups, teams, and societies and can therefore serve as the fundamental building blocks for what he calls Generative Social Science. The rational actor now has a true competitor. Agent_Zero is a major advance."--Scott Page, University of Michigan

"This is social science based on how our brains actually work. Epstein's computerized 'agents' can feel passion and fear, and can influence each other emotionally. And when they interact, we see many of the realities of social life, from the dynamics of juries to racist violence to Arab springs. A remarkable and original piece of work."--W. Brian Arthur, Santa Fe Institute

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Agent_Zero

Toward Neurocognitive Foundations for Generative Social Science

By Joshua M. Epstein

PRINCETON UNIVERSITY PRESS

Copyright © 2013 Princeton University Press
All rights reserved.

ISBN: 978-0-691-15888-4

Contents

Foreword, xi, 
Preface, xiii, 
Acknowledgments, xv, 
Introduction, 1, 
Part I. Mathematical Model, 19, 
Part II. Agent-Based Computational Model, 81, 
Part III. Extensions, 107, 
Part IV. Future Research and Conclusion, 181, 
Appendix I. Threshold Imputation Bounds, 195, 
Appendix II. Mathematica Code, 197, 
Appendix III. Agent_Zero NetLogo Source Code, 213, 
Appendix IV. Parameter Settings for Model Runs, 221, 
References, 227, 
Index, 243, 

CHAPTER 1

PART I

Mathematical Model

In this part, we specify explicit mathematical models for the emotional,deliberative, and social components of the Agent_Zero framework. Thesechoices are not cast in stone, and different components should certainly beexplored, as discussed in the Future Research section. First, however, we reviewsome underlying neuroscience of fear and its throne: the amygdala.

This review is worthwhile because the Rescorla-Wagner equations (usedfor the affective model component) do not presuppose that fear acquisition islargely unconscious, while this is a crucially important fact from a social sciencestandpoint, and the amygdala discussion demonstrates that it is a neuroscientificallysound modeling assumption. Also, important evidence of emotionalcontagion comes from fMRI studies of the amygdala, and if we didn'tknow anything about the amygdala, these images would mean very little.

Understanding, then, that unconscious fear acquisition is what we havein mind, we now discuss the elementary neuroscience of fear as prelude tothe famous Rescorla-Wagner equations of conditioning, all en route to ourmore general model of behavior in groups.

I.1. THE PASSIONS: FEAR CONDITIONING

Humans are born with a variety of innate endowments or capacities. Oneof these is the capacity to acquire fear (and other) associations through aprocess of synaptic change in which, as Donald Hebb (1949) presciently putit, "neurons that fire together wire together." That is, after certain pairingsof an initially neutral stimulus (e.g., a tone) and a stimulus that is innatelyaversive (e.g., a shock), the initially neutral stimulus will evoke the sameresponse as the innately aversive stimulus. This associative process—oftentermed conditioning—is generated by synaptic change, or "plasticity." For alucid nontechnical exposition, see LeDoux (2002). We, of course, cannot cutopen a human and observe her fear, but we can intelligently speak of a fearcircuit—a distributed neurochemical computational architecture—whoseproper functioning is of obvious evolutionary value and whose activation isstrongly correlated with physical, autonomic, and other observable symptomsof fear (e.g., freezing). Indeed, LeDoux and others have mapped thefear circuit's operation in considerable detail and have made huge stridesin explaining the observed capacity for associative fear acquisition, retention,and extinction by Hebbian plasticity and long-term potentiation at thecellular-synaptic level (LeDoux, 2002, pp. 79–80).

The same Hebbian picture is mirrored in the higher-level Rescorla-Wagner(RW) equations, which we shall employ in the affective componentof the model. These operate not at the neuronal level but at the level of theperson, or subject, where certain conditioning stimuli (the bell) become associatedwith specific unconditioned stimuli (the shock) through repeatedpairings. There is certainly an underlying mathematical theory of neuronalfunction (action potentiation and firing), of which the cornerstones are thefamous Hodgkin-Huxley model (Hodgkin and Huxley, 1952) and its relatives,notably the Fitzhugh-Nagamo (Fitzhugh, 1961) model. As suggestedearlier, one can imagine filling in the gap between the cellular-synaptic accountand the high-level RW equations with such intermediate models.This is an important scientific challenge. Here, we attempt only a crudeplausible synthesis of simple emotional, cognitive, and social components.But to begin at the beginning, let us examine some basic features of fear.

Fear Circuitry and the Perils of Fitness

A snake is suddenly thrown in your path. You automatically freeze. Why?From an evolutionary perspective, a reasonable hypothesis is that we freeze(are "scared stiff") because the predators faced by our evolutionary ancestorsused motion detection to home in on prey, and animals (i.e., species)that didn't freeze were wiped out. Animals hard-wired to freeze enjoyeda selective advantage, in other words, and have passed the relevant wiringdown as part of our genetic endowment.

Wiring: The Amygdala in a Nutshell

As LeDoux writes, "The basic wiring plan is simple: it involves the synapticdelivery of information about the outside world to the amygdala, and thecontrol of responses that act back on the world by synaptic outputs of theamygdala. If the amygdala detects something dangerous by its inputs (discussedfurther below) then its outputs are engaged. The result is freezing,changes in blood pressure and heart rate, release of hormones, and lots ofother responses that are either preprogrammed ways of dealing with dangeror are aspects of body physiology that support defensive behaviors." (LeDoux,2002, pp. 8–9). A simple depiction is given in Figure 1 for an auditorythreat stimulus.

Having classified an auditory stimulus as threatening (innately or throughconditioning), the auditory thalamus projects (emits an action potential) tothe lateral amygdala (LA) and auditory cortex, which also projects a morerefined signal to the LA. The central amygdala (CE) then activates varioussystems to produce responses, such as those shown: freezing, increases inblood pressure, and the release of various hormones. (Further responses arediscussed later.)

In somewhat greater detail, the neural mechanism of amygdala inputsand activation, and amygdala output, are conveyed in the diagrams of Figure2. Inputs are depicted in the top, and outputs are shown in the bottomdiagram (Figure 2).

The blue almond-shaped structure here corresponds to stunning micrographsof stained brain slices like the one shown below in Figure 3 (LeDoux,2008).

One essential point is that this architecture supports a critical delay betweenunconscious and conscious responses to stimuli.

Inputs: High Road and Low Road

For example, "auditory inputs reach the lateral amygdala from the auditorythalamus and auditory cortex ... These provide a rapid but impreciseauditory signal to the amygdala. Cortical inputs from the auditory andother sensory systems ... provide the amygdala with a more elaborate representationthan could come from the thalamic inputs. However, becauseadditional synaptic connections are involved, transmission is slower" (Ledoux,2007). Hence, LeDoux (2002) calls these "the low road and the highroad," as depicted in Figure 4.

I instantly freeze at the snake (low road) but then evaluate it as beinga benign garter snake (high road), not a true black mamba, for instance.While the extreme rapidity of the unconscious response is of immenseevolutionary value, we will see that, from a social standpoint, the lag betweenit and conscious appraisal is a decidedly mixed blessing.

Outputs

Continuing, "once the amygdala detects a threat, its outputs lead...

Details zur Ausgabe

• Verlag: Princeton University Press
• Erscheinungsdatum: 2014
• Sprache: Englisch
• ISBN 10: 0691158886
• ISBN 13: 9780691158884
• Einband: Gebundene Ausgabe
• Anzahl der Seiten: 249
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Buchbär; info@buchbaer.de; ; Weberstr. 67; Osnabrück; 49084; Deutschland