Statius Silvae 4. 9: Libertas Decembris?

published or submitted for publicatio

Cascades of Failure and Extinction in Evolving Complex Systems

There is empirical evidence from a range of disciplines that as the connectivity of a network increases, we observe an increase in the average fitness of the system. But at the same time, there is an increase in the proportion of failure/extinction events which are extremely large. The probability of observing an extreme event remains very low, but it is markedly higher than in the system with lower degrees of connectivity. We are therefore concerned with systems whose properties are not static but which evolve dynamically over time. The focus in this paper, motivated by the empirical examples, is on networks in which the robustness or fragility of the vertices is not given, but which themselves evolve over time We give examples from complex systems such as outages in the US power grid, the robustness properties of cell biology networks, and trade links and the propagation of both currency crises and disease. We consider systems which are populated by agents which are heterogeneous in terms of their fitness for survival. The agents are connected on a network, which evolves over time. In each period agents take self-interested decisions to increase their fitness for survival to form alliances which increase the connectivity of the network. The network is subjected to external negative shocks both with respect to the size of the shock and the spatial impact of the shock. We examine the size/frequency distribution of extinctions and how this distribution evolves as the connectivity of the network grows. The results are robust with respect to the choice of statistical distribution of the shocks. The model is deliberately kept as parsimonious and simple as possible, and refrains from incorporating features such as increasing returns and externalities arising from preferential attachment which might bias the model in the direction of having the empirically observed features of many real world networks. The model still generates results consistent with the empirical evidence: increasing the number of connections causes an increase in the average fitness of agents, yet at the same time makes the system as whole more vulnerable to catastrophic failure/extinction events on an near-global scale.Agent-Based Model; Connectivity; Complex Systems; Networks

Innovation and Reduction in Contemporary Qualitative Methods: The Case of Conceptual Coupling, Activity-Type Pairs and Auto-Ethnography

During the course of this paper we mobilise an ideal typical framework that identifies three waves of reduction within contemporary qualitative inquiry as they relate to key aspects of the sociological tradition. The paper begins with a consideration of one of sociology\'s key questions; namely how is social organisation possible? The paper aims to demonstrate how this question moves from view as increased specialisation and differentiation in qualitative methodology within sociology and related disciplines results in a fragmentation and decontextualisation of social practices from social orders. Indeed, the extent to which qualitative methods have been detached from sociological principles is considered in relation to the emergence of a reductionist tendency. The paper argues that the first wave is typified by conceptual couplings such as \'discourse and the subject\', \'narrative and experience\', \'space and place\' and the second by \'activity type couplings\' such as \'walking and talking\' and \'making and telling\' and then, finally, the third wave exemplified through auto-ethnography and digital lifelogging. We argue each of these three waves represent a series of steps in qualitative reduction that, whilst representing innovation, need to reconnect with questions of action, order and social organisation as a complex whole as opposed to disparate parts.Social Order, Discourse, Narrative, Mobile Methods, Auto-Ethnography, Reflexivity, Innovation, Qualitative Methods

Spatial Dynamics of Pandemic Influenza in a Massive Artificial Society

EpiSimS is a massive simulation of the movements, activities, and social interactions of individuals in realistic synthetic populations, and of the dynamics of contagious disease spread on the resulting social contact network. This paper describes the assumptions and methodology in the EpiSimS model. It also describes and presents a simulation of the spatial dynamics of pandemic influenza in an artificial society constructed to match the demographics of southern California. As an example of the utility of the massive simulation approach, we demonstrate a strong correlation between local demographic characteristics and pandemic severity, which gives rise to previously unanticipated spatial pandemic hotspots. In particular, the average household size in a census tract is strongly correlated with the clinical attack rate computed by the simulation. Public heath agencies with responsibility for communities having relatively high population per household should expect to be more severely hit by a pandemic.Agent Based Modeling, Computer Simulation, Epidemic Simulation, Public Health Policy

Can Extremism Guarantee Pluralism?

Many models have been proposed to explain the opinion formation in a group of individuals; most of these models study the opinion propagation as the interaction between nodes/agents in a social network. Opinion formation is a very complex process and a realistic model should also take into account the important feedbacks that the opinions of the agents have on the structure of the social networks and on the characteristics of the opinion dynamics. In this paper we will show that associating to different agents different kind of interconnections and different interacting behaviour can lead to interesting scenarios, like the co-existence of several opinion clusters, namely pluralism. In our model agents have opinions uniformly and continuously distributed between two extremes. The social network is formed through a social aggregation mechanism including the segregation process of the extremists that results in many real communities. We show how this process affects opinion dynamics in the whole society. In the opinion evolution we consider the different predisposition of single individuals to interact and to to modify each other's opinions; we associate to each individual a different tolerance threshold, depending on its own opinion: extremists are less willing to interact with individuals with strongly different opinions and to change significantly their ideas. A general result is obtained: when there is no interaction restriction, the opinion always converges to uniformity, but the same is happening whenever a strong segregation process of the extremists occurs. Only when extremists are forming clusters but these clusters keep interacting with the rest of the society, the survival of a wide opinion range is guaranteed.Extremists, Segregation, Opinion Dynamics

ODD Updated

An update to Volker Grimm and colleagues\' Overview, Design concepts and Details (ODD) protocol for documenting individual and agent based models (I/ABM) has recently been published in Ecological Modelling. This renames the \'State variables and scales\' element to \'Entities, state variables and scales\', and the \'Input\' element to \'Input data\', introduces two new Design concepts (\'Basic principles\' and \'Learning\'), and renames another (\'Fitness\' is now generalised to \'Objectives\'). The Design concepts element can now also be shortened such that it is not required to include any design concept that is irrelevant to the model, and expanded to include new design concepts more appropriate to the model being described. Other clarifications of intentions in the original protocol have been made.ODD, Individual Based Models, Agent Based Models, Replication, Documentation

It Pays to Be Popular: a Study of Civilian Assistance and Guerilla Warfare

This paper presents a study into the benefits imparted by friendly civilian populaces in assisting peacekeepers to conduct operations under the threat of guerrilla warfare. In this study, civilians report observed insurgent activity to peacekeepers with varying levels of enthusiasm depending on the reputation of the peacekeepers with the local populace. A simulation model is developed using an agent-based approach and a statistically significant number of Monte Carlo simulations conducted to measure the success of the peacekeeping operations and the benefits of civilian assistance.Peacekeeping, Insurgency, Agent-Based

For an Integrated Approach to Agent-Based Modeling of Science

The goal of this paper is to provide a sketch of what an agent-based model of the scientific process could be. It is argued that such a model should be constructed with normative claims in mind: i.e. that it should be useful for scientific policy making. In our tentative model, agents are researchers producing ideas that are points on an epistemic landscape. We are interested in our agents finding the best possible ideas. Our agents are interested in acquiring credit from their peers, which they can do by writing papers that are going to get cited by other scientists. They can also share their ideas with collaborators and students, which will help them eventually get cited. The model is designed to answer questions about the effect that different possible behaviors have on both the individual scientists and the scientific community as a whole.Agent-Based Models, Science Dynamics, Social Networks, Scientometrics, Evolutionary Computation

A Survey of Agent-Based Modeling Practices (January 1998 to July 2008)

In the 1990s, Agent-Based Modeling (ABM) began gaining popularity and represents a departure from the more classical simulation approaches. This departure, its recent development and its increasing application by non-traditional simulation disciplines indicates the need to continuously assess the current state of ABM and identify opportunities for improvement. To begin to satisfy this need, we surveyed and collected data from 279 articles from 92 unique publication outlets in which the authors had constructed and analyzed an agent-based model. From this large data set we establish the current practice of ABM in terms of year of publication, field of study, simulation software used, purpose of the simulation, acceptable validation criteria, validation techniques and complete description of the simulation. Based on the current practice we discuss six improvements needed to advance ABM as an analysis tool. These improvements include the development of ABM specific tools that are independent of software, the development of ABM as an independent discipline with a common language that extends across domains, the establishment of expectations for ABM that match their intended purposes, the requirement of complete descriptions of the simulation so others can independently replicate the results, the requirement that all models be completely validated and the development and application of statistical and non-statistical validation techniques specifically for ABM.Agent-Based Modeling, Survey, Current Practices, Simulation Validation, Simulation Purpose

Socio-Cultural Risk? Reporting on a Qualitative Study with Female Street-Based Sex Workers

Risk narratives are of increasing importance in contemporary social life in that they help in understanding and anticipating the shifts that characterise our late modern landscape. Our qualitative research explores risk as it relates to violence toward street-based sex workers in a suburban Australian setting. Female street-based sex workers represent a highly stigmatised and marginalised group. International studies report that they experience high levels of sexual violence perpetrated by male clients and our empirical work with street-based sex workers in Adelaide, South Australia concurs with this finding. Despite many creative and specialized skills workers reported drawing upon to minimise the risk of violence to themselves, we argue that a socio-cultural lens is vital to viewing risk in this context. We argue that in order to effect change, risk must be disembedded from increasingly individualized discourses, since it is through the personalisation of risk that violence becomes legitimised as an occupational hazard in street-based sex work.Sex Work, Prostitution, Risk, Gender, Gendered Violence, Socio-Cultural Risk Theory, Disembedding Risk