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News Category: ‘Past Friday Seminars’

CSS SEMINAR – MAY 7 – MOREL

Friday, 7th May: 3.00pm

Can Real Options Be Made A Stand-alone Paradigm? From Risk Neutrality to Swiss Neutrality

Benoit Morel, Associate Teaching Professor
Engineering and Public Policy and Physics
Carnegie Mellon University

Financial option theory has changed the landscape in the pursuit of rigorous way to analyze decisions under uncertainty and risks. The extension to that theory outside of the confines of finances, the so-called “real option theory”, has not yet delivered on its early promises. It has developed into a cacophony of ad hoc approaches. In this talk I want to report on an attempt to ground the paradigm of real options on solid mathematical foundations.

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CSS SEMINAR – MAY 14 – ROOT

Friday, 14th May: 3.00pm

The Sciences of Complexity and Global Governance

Professor Hilton Root
School of Public Policy
George Mason University

Professor Root will be discussing two chapters from his upcoming book. The chapters are “The Co-evoluntionary Dynamics of Globalization” & “The Rise of the Modern State: Gradual Reform or Punctuated Transition.”

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CSS SEMINAR – SEPTEMBER 10 – TSVETOVAT

Friday, September 10: 3:00pm

Strategies for Successful Study for the PhD in Computational Social Science

Professor Maksim Tsvetovat
Computational Social Science

On Friday, September 10, Professor Max Tsvetovat, Director of Graduate Studies, will discuss strategies for successful study for the Ph.D. in Computational Social Science. After that there will be a discussion of open extramural funding opportunities relevant to computational social science, with the possible self-organization of coalitions around the most fertile ones.

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CSS SEMINAR – SEPTEMBER 17 – LATEK and RIZI

Friday, September 17: 3:00pm

Merging Remote Sensing Data and Population Surveys in Large, Empirical Multiagent Models: The Case of the Afghan Drug Industry

Maciek M. Latek, CSS PhD Candidate
Seyed M.M. Rizi, CSS PhD Candidate

On Friday, September 17, Maciej Latek and Seyed Rizi will present “Merging Remote Sensing Data and Population Surveys in Large, Empirical Multiagent Models: The Case of the Afghan Drug Industry” a project they have been working on with Armando Geller, Research Faculty.

Links between licit and illicit economies fuel processes of conflict in countries mired in irregular warfare. However, it is often infeasible to gather demographic and economic data in the war zone that illuminate such links. Combining remote sensing data with local surveys offers an alternative to direct data collection. We present and validate an implementation of such an approach in order to recover an agentized household representation of the rural population in Afghanistan where poppy cultivation and opium trafficking have in influenced the course of the current conflict significantly.

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CSS SEMINAR – OCTOBER 8 – ABDUKADIROV

Friday, October 8: 3:00pm

Emergence of Political Parties during Democratic Transitions: An Agent-based Approach

Sherzod Abdukadirov, PhD Candidate
School of Public Policy
George Mason University

In order to model possible scenarios of political liberalization it is important to explore what political parties are likely to emerge in the case of transition. The impact of the institutional design and underlying social structure on the emerging party system is particularly crucial. Therefore, this research focuses on the following broad questions: (1) the types of parties likely to emerge in a given society under different institutional designs; (2) probability of a fundamentalist party coming to power; (3) the level of volatility of the party system. The research utilizes agent-based modeling approach.

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CSS SEMINAR – OCTOBER 15 – SCOTT

Friday, October 15: 3:00pm

Strategic Adaptation in Spatial Evolutionary Games

Steve Scott, PhD Student
Department of Computational Social Science
George Mason University

Evolutionary Game Theory (EGT) has been used in the natural sciences to study population dynamics and in the social sciences for the study of group behaviors. Evolutionary game theory is based on the concept that the proportional distribution of the various types in the population will converge to a long-term steady state based on the greater reproductive success of individuals having higher fitness in the population. Spatial evolutionary game theory uses the classical evolutionary game theory concepts to govern population dynamics, but uses spatial constraints to limit interactions between agents based on their location.

Classical EGT models make certain simplifying assumptions, such as complete random mixing among members of the population, infinite population sizes, and no mutation. This study relaxes these assumptions and investigates a combination of two extensions to classical EGT – the use of spatially explicit representation to localize agent interaction, and several methods for modifying agent strategy preferences over time. The model considers the effect of synchronous versus asynchronous strategy updating, the use of pure strategy versus mixed strategy profiles, the effect of neighborhood size on strategic adaptation, and the effect of local versus neighborhood influences on strategic adaptation in a Particle Swarm Optimization (PSO) environment.

A spatial agent-based model is used in which a set of stationary agents interact with nearby agents in a repeated-play Prisoner’s Dilemma game in order to explore the tension between cooperative and competitive strategy adaptation over time. Agents play the game with their neighbors, and decide whether to pursue a cooperative or competitive strategy based on a comparison of their own payoff with the payoffs of their neighbors, adopting the strategy that yields the best outcome. The population strategy preferences change over time as the strategy preferences of many individual neighborhoods emerge.

The modeling results indicate that the population strategy preference between cooperation and competition in populations using mixed strategies is markedly different from populations using only pure strategies. In addition, the results show that population preferences for cooperation and competition are sensitive to neighborhood size. Finally, when comparing the effects of local influence versus neighborhood influence in a PSO environment, the effect of the neighborhood strategy choice appears to be much more significant than the effect of the local strategy choice or the interaction between the local and neighborhood effects. The results are of interest in the study of the strategic adaptation of population preferences over time, especially in spatially constrained environments.

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CSS SEMINAR – OCTOBER 22 – STONE

Friday, October 22 3:00 p.m.

Quorum Sensing in Bacteria

Steve Stone, JD (Yale)
M.Ed. Student
George Mason University

Quorum sensing refers to the ability of bacteria to detect the presence of other bacteria. When a “quorum” of nearby bacteria is detected, genes coding for group behaviors may be up-regulated, causing the bacterium to switch lifestyles — e.g., from a free-swimming “planktonic” form, to a colonial form living as, e.g., (1) a sessile biofilm, (2) an aggressive “swarming” colony attacking an infected host, or (3) in one well-studied case, a colony of symbiotic bacteria producing light to assist in camouflaging a small squid.

The general mechanism of quorum sensing may be summarized as follows:

Each bacterium secretes chemical signals called “autoinducers” into the local aqueous environment. When detected in sufficient concentration these signaling molecules indicate the presence of a critical mass of nearby bacteria. The detection of a threshold level of autoinducer molecules triggers a conformational change in a receptor protein, opening a DNA binding domain on the receptor protein that then binds to the promoter region for an “operon” — a cluster of genes coding for a group of related proteins. The proteins coded for by the up-regulated operon are essential to the expression of group behaviors such as launching an attack against a host organism or forming a
biofilm — behaviors would be ineffective and wasteful if undertaken by a single bacterium.

Quorum sensing can involve either a particular species of bacteria, or generic signaling that is recognized and responded to across many species of bacteria. An example of the latter
is the formation of films of bacteria on our teeth each night.

Quorum sensing enables very small organisms to “band together” to adopt mutually beneficial
adaptive behaviors and use limited resources more efficiently and effectively. It also enables organisms with a small genome to effectively adopt a different phenotype (a different set of
expressed genes) when circumstances (i.e. presence of other bacteria) permit.

Computer modeling of quorum sensing is an active area of research.

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CSS SEMINAR – NOVEMBER 12 – ANDERSON and AKTIPIS

Friday, November 12 – 3:00 p.m.

The Origins of Collective Overvaluation: Irrational exuberance emerges from simple, honest and rational individual behavior

Michael Anderson, PhD
Department of Psychology
Franklin & Marshall College

C. Athena Aktipis, PhD
Department of Ecology and Evolutionary Biology
University of Arizona

The generation of value bubbles is an inherently psychological and social process, where information sharing and individual decisions can affect representations of value. Bubbles occur in many domains, from the stock market, to the runway, to the laboratories of science. Here we seek to understand how psychological and social processes lead
representations (i.e., expectations) of value to become divorced from the inherent value, using asset bubbles as an
example. Using an agent-based model we explore whether a simple switching rule can generate irrational exuberance, and systematically explore how communication between decision makers influences the speed and intensity of overvaluation. We show that rational and simple individual level rules combined with honest information sharing are sufficient to generate the collective overvaluation characteristic of irrational exuberance. Further, our results demonstrate that simple noise in the exchange of value information leads to rapidly increasing expectations about value, even when no one is engaged in exaggerating their expectations for the assets they own.

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CSS SEMINAR – DECEMBER 3 – AXTELL

Friday, December 3 – 3:00 p.m.

Endogenous Macroeconomic Fluctuations from Purely Microeconomic Phenomena in a Model with 150 Million Agents

Robert Axtell, Chair
Department of Computational Social Science
George Mason University

ABSTRACT: Conventional macroeconomic models have microeconomic specifications in which the agents (workers, firms, consumers) who make up the economy are assumed to be in general equilibrium. As a result, the only sources of dynamics in such model economies are external shocks. These shocks are treated as stochastic, ostensibly outside the bounds of normal economic theorizing. However, a wide-range of economic downturns and financial crises appear to have no external cause, but rather seem to be due to processes internal to their underlying economies. Here we show that a microeconomic model, written at the level of individual economic agents, can endogenously produce macroeconomic dynamics that closely resemble those of modern macroeconomies: idiosyncratic business cycles, waves of involuntary unemployment, irregular exponential growth, spontaneous firm birth and death, job turnover, skew income distributions, fluctuating prices, power law distributions of firm sizes, heavy-tailed firm growth rates, and inflation. The model is built from millions of software agents and realized computationally. Agents work in team production environments, are paid wages, migrate between firms based on job opportunities, and start new firms when they perceive it advantageous to do so. Prices are local and fluctuate endogenously. Consumers seek utility by purchasing goods from firms. Firms come and go based on sales and profitability. Microeconomic equilibria exist but are dynamically unstable. No macroeconomic specifications of any kind are employed in the model. Overall, aggregate structure emerges endogenously from the bottom up, through the interactions of the purposive agents. Specifically, the aggregate economy expands with fluctuations about a steady-state growth rate while the agent level is always out of equilibrium. As the economy grows the fluctuations decay in a peculiar way that is consistent with empirical data.

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CSS SEMINAR – DECEMBER 10 – ORMEROD

Friday, December 10 – 3:00 p.m.

Paul Ormerod
Volterra Consulting

Paul Ormerod of Volterra Consulting will be discussing various topics they have been working on including models of binge drinking and related social phenomena.

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