Conventions spreading in open-ended systems

We introduce a simple open-ended model that describes the emergence of a shared vocabulary. The ordering transition toward consensus is generated only by an agreement mechanism. This interaction defines a finite and small number of states, despite each individual having the ability to invent an unlimited number of new words. The existence of a phase transition is studied by analyzing the convergence times, the cognitive efforts of the agents and the scaling behavior in memory and timeComment: 11 pages, 5 figure

Sharp transition towards shared vocabularies in multi-agent systems

What processes can explain how very large populations are able to converge on the use of a particular word or grammatical construction without global coordination? Answering this question helps to understand why new language constructs usually propagate along an S-shaped curve with a rather sudden transition towards global agreement. It also helps to analyze and design new technologies that support or orchestrate self-organizing communication systems, such as recent social tagging systems for the web. The article introduces and studies a microscopic model of communicating autonomous agents performing language games without any central control. We show that the system undergoes a disorder/order transition, going trough a sharp symmetry breaking process to reach a shared set of conventions. Before the transition, the system builds up non-trivial scale-invariant correlations, for instance in the distribution of competing synonyms, which display a Zipf-like law. These correlations make the system ready for the transition towards shared conventions, which, observed on the time-scale of collective behaviors, becomes sharper and sharper with system size. This surprising result not only explains why human language can scale up to very large populations but also suggests ways to optimize artificial semiotic dynamics.Comment: 12 pages, 4 figure

Complex systems approach to language games

The mechanisms leading language conventions to be socially accepted and adopted by a group are object of an intense debate. The issue can be of course addressed by different points of view, and recently also complex system science has started to contribute, mainly by means of computer simulations and analytical approaches. In this paper we study a very simple multi-agent model of convention spreading and investigate some of the crucial aspects of its dynamics, resorting, whenever possible, to quantitative analytic methods. In particular, the model is able to account for the emergence of global consensus out of local (pairwise) interactions. In this regard, a key question concerns the role of the size of the population. We investigate in detail how the cognitive efforts of the agents in terms of memory and the convergence time scale with the number of agents. We also point out the existence of an hidden timescale ruling a fundamental aspect of the dynamics, and we discuss the nature of the convergence process

Citizen noise pollution monitoring

Trabajo presentado a la 10th Annual International Conference on Digital Government Research: Social Networks: Making Connections between Citizens, Data and Government, celebrada en Puebla (México) del 17 al 21 de mayo de 2009.In this paper we present a new approach to monitor noise pollution involving citizens and built upon the notions of participatory sensing and citizen science. We enable citizens to measure their personal exposure to noise in their everyday environment by using GPS-equipped mobile phones as noise sensors. The geo-localised measures and user-generated meta-data can be automatically sent and shared online with the public to contribute to the collective noise mapping of cities. Our prototype, called NoiseTube, can be found online.This work was partially supported by the EU under contract IST- 34721 (TAGora). The TAGora project is funded by the Future and Emerging Technologies program (IST-FET) of the European Commission. Matthias Stevens is a Research Assistant of the Fund for Scientific Research, Flanders (Aspirant van het Fonds Wetenschappelijk Onderzoek - Vlaanderen).Peer reviewe

Self-organizing communication in language games

From the point of view of semiotic dynamics language is an evolving complex dynamical system. In this perspective, unrevealing the mechanisms that allow for the birth of shared conventions is a major issue. Here we describe a very simple model in which agents negotiate conventions and reach a global agreement without any intervention from the outside. In particular we focus on the possibility of predicting on which of the several competing conventions the agreement is reached. We find from simulations that early created conventions are favored in the competition process and this advantage can be quantified. Beyond the specific results presented here, we think that this paper provides an example of a new way of investigating language features where simple models allow for the investigation of precise problems and, possibly, for analytical approaches

In-depth analysis of the Naming Game dynamics: the homogeneous mixing case

Language emergence and evolution has recently gained growing attention through multi-agent models and mathematical frameworks to study their behavior. Here we investigate further the Naming Game, a model able to account for the emergence of a shared vocabulary of form-meaning associations through social/cultural learning. Due to the simplicity of both the structure of the agents and their interaction rules, the dynamics of this model can be analyzed in great detail using numerical simulations and analytical arguments. This paper first reviews some existing results and then presents a new overall understanding.Comment: 30 pages, 19 figures (few in reduced definition). In press in IJMP

Consensus formation on adaptive networks

The structure of a network can significantly influence the properties of the dynamical processes which take place on them. While many studies have been devoted to this influence, much less attention has been devoted to the interplay and feedback mechanisms between dynamical processes and network topology on adaptive networks. Adaptive rewiring of links can happen in real life systems such as acquaintance networks where people are more likely to maintain a social connection if their views and values are similar. In our study, we consider different variants of a model for consensus formation. Our investigations reveal that the adaptation of the network topology fosters cluster formation by enhancing communication between agents of similar opinion, though it also promotes the division of these clusters. The temporal behavior is also strongly affected by adaptivity: while, on static networks, it is influenced by percolation properties, on adaptive networks, both the early and late time evolution of the system are determined by the rewiring process. The investigation of a variant of the model reveals that the scenarios of transitions between consensus and polarized states are more robust on adaptive networks.Comment: 11 pages, 14 figure

A new single nephron model of focal and segmental glomerulosclerosis in the Munich-Wistar rat

A new single nephron model of focal and segmental glomerulosclerosis in the Munich-Wistar rat. The hypothesis that damage to the visceral epithelial cell plays a central role in the pathogenesis of focal and segmental glomerulosclerosis was tested by injecting saponin solutions of increasing concentration (0.1, 0.3, 0.6 and 1.0 mg/ml) in Bowman's space of superficial glomeruli in the Munich-Wistar rat. The microinjections were performed both with and without intermittent clamping of the renal vessels during two minutes. After 8 to 14 days the injected glomeruli were examined by light microscopy. The injected glomeruli were classified as, normal (NL), showing visceral epithelial cell damage (VECD), showing focal and segmental glomerulosclerosis (FSGS) or showing global sclerosis (GS). Swelling and intracellular vacuolation of the visceral epithelial cells (VEC) were considered as VECD. FSGS-lesions were seen most frequently in the glomeruli injected with 10 nl of a saponin solution with a concentration higher than 0.3 mg/ml. In view of the light microscopic lesions four glomeruli in a 0 mg/ml, the 0.1 mg/ml and the 0.6 mg/ml saponin groups were examined after 40 minutes with transmission electron microscopy (TEM) to evaluate the selectivity of the lesions. In the 0 and 0.1 mg/ml group only occasional limited fusion of the foot processes of the podocytes was seen. In the 0.6 mg/ml group segmental lysis of the VEC without ultrastructural damage to the capillary basement membrane or the endothelial and mesangial cells was seen. It is concluded that it is possible to induce direct segmental lysis of the visceral epithelial cells in a single glomerulus, and that this damage to the visceral epithelial cells is related to the development of focal and segmental glomerulosclerosis