Culture-area relation in Axelrod's model for culture dissemination

Axelrod's model for culture dissemination offers a nontrivial answer to the question of why there is cultural diversity given that people's beliefs have a tendency to become more similar to each other's as people interact repeatedly. The answer depends on the two control parameters of the model, namely, the number $F$ of cultural features that characterize each agent, and the number $q$ of traits that each feature can take on, as well as on the size $A$ of the territory or, equivalently, on the number of interacting agents. Here we investigate the dependence of the number $C$ of distinct coexisting cultures on the area $A$ in Axelrod's model -- the culture-area relationship -- through extensive Monte Carlo simulations. We find a non-monotonous culture-area relation, for which the number of cultures decreases when the area grows beyond a certain size, provided that $q$ is smaller than a threshold value $q_c = q_c (F)$ and $F \geq 3$. In the limit of infinite area, this threshold value signals the onset of a discontinuous transition between a globalized regime marked by a uniform culture (C=1), and a completely polarized regime where all $C = q^F$ possible cultures coexist. Otherwise the culture-area relation exhibits the typical behavior of the species-area relation, i.e., a monotonically increasing curve the slope of which is steep at first and steadily levels off at some maximum diversity value

Opinion dynamics on interacting networks: Media competition and social influence

The inner dynamics of the multiple actors of the informations systems - i.e, T.V., newspapers, blogs, social network platforms, - play a fundamental role on the evolution of the public opinion. Coherently with the recent history of the information system (from few main stream media to the massive diffusion of socio-technical system), in this work we investigate how main stream media signed interaction might shape the opinion space. In particular we focus on how different size (in the number of media) and interaction patterns of the information system may affect collective debates and thus the opinions' distribution. We introduce a sophisticated computational model of opinion dynamics which accounts for the coexistence of media and gossip as separated mechanisms and for their feedback loops. The model accounts also for the effect of the media communication patterns by considering both the simple case where each medium mimics the behavior of the most successful one (to maximize the audience) and the case where there is polarization and thus competition among media memes. We show that plurality and competition within information sources lead to stable configurations where several and distant cultures coexist

Multi-Agenten-Modelle

Multi-Agenten-Modellierung ist eine Form der Computermodellierung die darauf abzielt zu erklären, wie soziale Phänomene aus dem komplexen Zusammenspiel interdependenter Individuen entstehen. Der vorliegende Beitrag gibt eine kurze Einführung in die Grundlagen sozialwissenschaftlicher Multi-Agenten-Modellierung. Wir besprechen dabei wichtige Modellierungsentscheidungen und Modellierungsalternativen. Am Anwendungsbeispiel der Erklärung von Meinungsdiversität wird illustriert, wie Simulationsexperimente mit einem Multi-Agenten-Modell und inhaltliche sozialwissenschaftliche Theoriebildung aufeinander bezogen werden können. Auf Basis der Programmiersprache NetLogo legen die Autoren das Modell als einfaches Beispielprogramm vor. Abschließend werden methodologische Prinzipien und Probleme der Multi-Agenten-Modellierung besprochen und Hinweise auf weiterführende Literatur gegeben