2014 Graduate Workshop in Complexity and Computational Social Science
Each student began a research project during the two-week
workshop. Below are brief descriptions of these various projects.
These projects will form the basis for dissertation chapters and/or
Christoph Aymanns, Mathematics, Oxford (firstname.lastname@example.org).
Christoph is exploring how assets and short-term funding markets interact to potentially
cause feedback loops that could ignite a financial crisis. In the model, exogenous changes in
asset prices may necessitate the selling off of assets by leveraged borrowers needing
to meet their lender's margin calls. To fully assess the stability of the system, he
analyzes a dynamic model and finds that as market impact grows, destabilizing feedback loops
can emerge leading to fat-tailed and asymmetric (on the loss side) return distributions. As assets
become more interdependent, the tradeoff between contagion and diversification can potentially
enhance the stability of the system.
Uttam Bhat, Physics, Boston U. (email@example.com).
Uttam is analyzing the relationship between weak ties and human migration. He begins by assuming that the
population is distributed across communities according to Zipf's law and that social networks are
created within cities via random graphs and preferential attachment. Anytime someone migrates, they
maintain their previous (but now weakened) ties to their community. Migration occurs by two mechanism in
the model: 1) a small fraction of people migrate according to a traditional gravity-model of migration and
2) migration is also linked to a Poisson process based on a gravity-like model driven by the number
of ties in the target versus the source community.
Cynthia Cors, Wilder School of Government and Public Affairs, Virginia Commonwealth U. (firstname.lastname@example.org).
Cindy wants to understand the supply of primary-care physicians (PCPs) in the medicaid program. The low
rates of reimbursement, the difficulty of the medical conditions, and the scheduling reliability of
medicaid patients often result in PCPs not taking on such patients. She focuses on the role of peer effects
among the PCPs, using a model that was initially developed to track changes in languages, here, repurposed to
track the willingness of PCPs to accept medicaid patients. She finds that, depending on a couple of parameters,
the system can easily fall into one of two attractors, one in which every PCP accepts medicaid
patients and one in which few do.
Matt L. Miller, Psychology, UC Davis (email@example.com).
Matt is developing a model of emerging altruism among foragers. He sets up a system with
foragers who reside in a central-place. Agents in the model must decide whether to forage---an action that comes
with an additional cost but with the potential for food acquisition---and also how much of whatever perishable food
they acquire to personally consume versus leaving at the central-place. Initial findings indicate that as
the potential for food begins to rise above subsistance, sharing begins to emerge with few free riders,
and the system can maintain this state as the food supply increases.
Nate Neligh, Economics, Columbia U. (firstname.lastname@example.org).
Nate is modeling scientific search on a rugged landscape. Researchers develop expertise on parts of
the landscape either by doing original research or learning from others (by paying a price tied to market
forces). The difficulty of acquiring new knowledge is tied to how far away that knowledge is from
an agent's existing expertise. On simple landscapes with limited memory, the system quickly converges to
the researchers closely clustered on good, but not optimal, outcomes, with researchers unwilling to
teach others. As search cost decrease, the system still concentrates the research effort, but this may
be on either high or low performing outcomes. Preliminary results suggest some surprising tradeoffs
between learning and researching incentives.
Paola D'Orazio, Philosophical, Pedagogical and Economic-Quantitative Sciences, U. "G.D'Annunzio" Chieti-Pescara (email@example.com).
Paola is interested in understanding how consumer lending can lead to instability in the economy.
Consumers receive wages and potentially borrow from a bank to support further
consumption based on their past employment experience
and beliefs about their future opportunities. Preliminary results indicate that the system
can result in periodic loan crises where the banking sector calls in consumer loans, result in
Oana Vuculescu, Business and Social Sciences, Aarhus U. (firstname.lastname@example.org).
Oana is intrigued by the diffusion of technological building blocks that can occur during
Agents can either explore around the technologies that they already know or they can acquire, in whole or
in part, the technologies of others.
She finds that there are some ways to organize collective-problem solving that allow individuals to use
"spurious" learning to discover high-quality technologies.
Amy Warren, Anthropology, U. of Missouri (email@example.com).
Amy is refining our understanding of disaggregation in agent-based models. Agent-based
models often incorporate certain degrees of aggregation, for example, using households
as the focal agent rather than the individuals in that household.
She finds that disaggregation can make dramatic changes in the prediction of
these model---for example, fertility rates can vary by a factor of two when
one moves from household to individual agents.
Alex Wood-Doughty, Economics, UC Santa Barbara (firstname.lastname@example.org).
Alex is intrigued about what conditions allow an online community to provide
quality information. In his work, agents have both a quality of knowledge and a fundamental
belief about the right answer. Agents benefit from sharing information when
their beliefs are divergent with the community. His subsequent analysis is
able to tie a couple of core parameters to the expexted amount of sharing in
the community and, ultimately, the likely quality of the answer that
Huanren (Warren) Zhang, Economics, Purdue U. (email@example.com).
Warren is looking at the impact of uncertainty on cooperation. He uses a game-theoretic model
where the players are subject to action errors while playing the Prisoner's Dilemma.
Warren evolves simple computer programs (finite automata) to explore this system, using various metrics
to track the strategic behavior that emerges in the system.
He finds that the system is able to evole high levels of cooperation after an
intitial period of defection. As the degree of uncertainty increases, the
strategies become both more lenient (that is, less likely to react
to defection) and more forgiving after a defection---a result that accords well
with some recent human experiments.
John H. Miller , firstname.lastname@example.org.