http://www.mdpi.com/journal/games/special_issues/soc-net-form/ Dear Colleagues, Research on (social) networks and network formation is well-established in the community of sociologists. During the past decade an increasing number of economists, especially game theorists, became interested in this topic as well. Regarding networking decisions as strategic decisions that are made by participants in a well defined non-cooperative game, opened a novel approach to network formation. Meanwhile, substantial empirical evidence has been accumulated emphasizing the important role of social and economic networks in real world economies. Famous examples of network effects can be found in job search, granting of credits, welfare participation or even in traffic control. Given the increasing importance of network research in social sciences, the journal Games will publish a Special Issue devoted to this topic. Reviews and original papers are welcome. Topics that touch upon the strategic aspect of network formation are appropriate for this special issue. Contributions from different disciplines besides economics (like, for example, sociology, natural sciences) are welcome. Prof. Dr. Siegfried K. Berninghaus Guest Editor {snippet name="submission_info"} http://www.mdpi.com/2073-4336/1/4/422/ In this note we introduce different levels of decay in the Goyal, Galeotti and Kamphorst (GGK) insider-outsider model of network formation. First, we deal with situations where the amount of decay is sufficiently low to avoid superfluous connections in strict Nash networks and we examine the architectures of strict Nash networks. We show that centrality and small diameter are robust features of strict Nash networks. Then, we study the Nash and efficient networks when the decay vanishes. http://www.mdpi.com/2073-4336/1/4/422/ Wed, 20 Oct 2010 00:00:00 CEST Games 2010-10-20 1 4 Article 422 437 2073-4336 The Insider-Outsider Model Reexamined 2010-10-20 doi: 10.3390/g1040422 Pascal Billand Christophe Bravard Sudipta Sarangi http://www.mdpi.com/2073-4336/1/4/438/ We study social learning in a large population of agents who only observe the actions taken by their neighbours. Agents have to choose one, out of two, reversible actions, each optimal in one, out of two, unknown states of the world. Each agent chooses rationally, on the basis of private information and of the observation of his neighbours’ actions. Agents can repeatedly update their choices at revision opportunities that they receive in a random sequential order. We show that if agents receive equally informative signals and observe both neighbours, then actions converge exponentially fast to a configuration where some agents are permanently wrong. In contrast, if agents are unequally informed (in that some agents receive a perfectly informative signal and others are uninformed) and observe one neighbour only, then everyone will eventually choose the correct action. Convergence, however, obtains very slowly, at rate √t. http://www.mdpi.com/2073-4336/1/4/438/ Wed, 20 Oct 2010 00:00:00 CEST Games 2010-10-20 1 4 Article 438 458 2073-4336 Bayesian Social Learning with Local Interactions 2010-10-20 doi: 10.3390/g1040438 Antonio Guarino Antonella Ianni http://www.mdpi.com/2073-4336/1/4/395/ This paper focuses on the dynamic aspects of individual behavior affected by its social embedding, either at large (society-wide norms or averages) or at a local neighborhood. The emphasis is on how initial conditions can affect the long run outcome and to derive, discuss and apply the conditions for such thresholds. For this purpose, intertemporal social pressure (from peers, from norms, or from fashions) is modelled in two different ways: (i) individual benefit is influenced by the possession of a stock (in the application: weight) and the society wide average, and (ii) individual benefits depend on a norm that follows its own motion, of course driven by agents’ behavior. The topical issue of obesity serves as motivation and corresponding models and examples are presented and analyzed. http://www.mdpi.com/2073-4336/1/4/395/ Wed, 13 Oct 2010 00:00:00 CEST Games 2010-10-13 1 4 Article 395 414 2073-4336 Modelling Social Dynamics (of Obesity) and Thresholds 2010-10-13 doi: 10.3390/g1040395 Franz Wirl Gustav Feichtinger http://www.mdpi.com/2073-4336/1/4/357/ If actors want to reach a particular goal, they are often better off forming collaborative relations and investing together rather than investing separately. We study the coordination and cooperation problems that might hinder successful collaboration in a dynamic network setting. We develop an experiment in which coordination problems are mainly due to finding partners for collaboration, while cooperation problems arise at the investment levels of partners who have already agreed to collaborate. The results show that as costs of forming links increase, groups succeed less often in solving the coordination problem. Still, if subjects are able to solve the coordination problem, they invest in a suboptimal way in the network good. It is mostly found that if cooperation is successful in terms of investment, it is due to subjects being able to monitor how much their partners invest. Moreover, subjects deal better with the coordination and cooperation problems as they gain experience. http://www.mdpi.com/2073-4336/1/4/357/ Tue, 28 Sep 2010 00:00:00 CEST Games 2010-09-28 1 4 Article 357 380 2073-4336 Coordination and Cooperation Problems in Network Good Production 2010-09-28 doi: 10.3390/g1040357 Antonie Knigge Vincent Buskens http://www.mdpi.com/2073-4336/1/3/317/ Human social networks reshape continuously, as individuals forge new contacts while abandoning existing ones. Simultaneously, individuals adapt their behavior, leading to an intricate interplay been network evolution and behavior evolution. Here, we review a framework, called Active Linking, which allows an analytical treatment of such a co-evolutionary dynamics. Using this framework we showed that an increase in the number of ways of responding to adverse interactions leads an overall increase of cooperation, which is here extended to all two-player social dilemmas. In addition, we discuss the role of the selection pressure in these results. http://www.mdpi.com/2073-4336/1/3/317/ Fri, 17 Sep 2010 00:00:00 CEST Games 2010-09-17 1 3 Article 317 337 2073-4336 Coevolution of Cooperation, Response to Adverse Social Ties and Network Structure 2010-09-17 doi: 10.3390/g1030317 Sven Van Segbroeck Francisco C. Santos Jorge M. Pacheco Tom Lenaerts http://www.mdpi.com/2073-4336/1/3/262/ We analyze dynamic local interaction in population games where the local interaction structure (modeled as a graph) can change over time: A stochastic process generates a random sequence of graphs. This contrasts with models where the initial interaction structure (represented by a deterministic graph or the realization of a random graph) cannot change over time. http://www.mdpi.com/2073-4336/1/3/262/ Tue, 10 Aug 2010 00:00:00 CEST Games 2010-08-10 1 3 Article 262 285 2073-4336 Local Interaction on Random Graphs 2010-08-10 doi: 10.3390/g1030262 Siegfried Berninghaus Hans Haller http://www.mdpi.com/2073-4336/1/3/242/ We propose a model in which agents of a population interacting according to a network of contacts play games of coordination with each other and can also dynamically break and redirect links to neighbors if they are unsatisfied. As a result, there is co-evolution of strategies in the population and of the graph that represents the network of contacts. We apply the model to the class of pure and general coordination games. For pure coordination games, the networks co-evolve towards the polarization of different strategies. In the case of general coordination games our results show that the possibility of refusing neighbors and choosing different partners increases the success rate of the Pareto-dominant equilibrium. http://www.mdpi.com/2073-4336/1/3/242/ Thu, 29 Jul 2010 00:00:00 CEST Games 2010-07-29 1 3 Article 242 261 2073-4336 Coordination Games on Dynamical Networks 2010-07-29 doi: 10.3390/g1030242 Marco Tomassini Enea Pestelacci http://www.mdpi.com/2073-4336/1/3/226/ We study the stability of social and economic networks when players are farsighted. We first provide an algorithm that characterizes the unique pairwise and groupwise farsightedly stable set of networks under the componentwise egalitarian allocation rule. We then show that this set coincides with the unique groupwise myopically stable set of networks but not with the unique pairwise myopically stable set of networks. We conclude that, if groupwise deviations are allowed then whether players are farsighted or myopic does not matter; if players are farsighted then whether players are allowed to deviate in pairs only or in groups does not matter. http://www.mdpi.com/2073-4336/1/3/226/ Thu, 22 Jul 2010 00:00:00 CEST Games 2010-07-22 1 3 Article 226 241 2073-4336 A Characterization of Farsightedly Stable Networks 2010-07-22 doi: 10.3390/g1030226 Gilles Grandjean Ana Mauleon Vincent Vannetelbosch http://www.mdpi.com/2073-4336/1/2/103/ I study the speed of the evolutionary process on small heterogeneous graphs using the Hawk-Dove game. The graphs are based on empirical observation data of grooming interactions in 81 primate groups. Analytic results for the star graph have revealed that irregular graphs can slow down the evolutionary process by increasing the mean time to absorption. Here I show that the same effects can be found for graphs representing natural animal populations which are much less heterogeneous than star graphs. Degree variance has proven to be a good predictor for the mean time to absorption also for these graphs. http://www.mdpi.com/2073-4336/1/2/103/ Thu, 06 May 2010 00:00:00 CEST Games 2010-05-06 1 2 Article 103 116 2073-4336 The ‘Hawk-Dove’ Game and the Speed of the Evolutionary Process in Small Heterogeneous Populations 2010-05-06 doi: 10.3390/g1020103 Voelkl