Individual and global adaptation in networks

Annales d'Economie et de …, 2007

the paper first introduces a general dynamic setup that embodies abstract formulations of the following two forces: (a) homophily, i.e. the idea that networking is favored by similarity in behavior; (b) conformity, i.e. the pressure towards similar behavior induced by interaction. this general framework is then specialized into three alternative directions, corresponding to different specific manifestations of those two forces. For each such particularization of the general model, we find that (i) sharp transitions, (ii) hysteresis, and (iii) equilibrium multiplicity are salient characteristics of the long-run social dynamics. since features (i)-(iii) are often reported for a variety of social (network) phenomena where (a)-(b) play an important role, we sugget that the former may indeed be the result of some common mechanism at work that relies on the interplay of the latter.

2006

The role of individual choice in the evolution of social complexity. -Ann. Zool. Fennici 44: 58-69.

eprint arXiv:1110.0376, 2011

Previous work has shown that species interacting in an ecosystem and actors transacting in an economic context may have notable similarities in behavior. However, the specific mechanism that may underlie similarities in nature and human systems has not been analyzed. Building on stochastic food-web models, we propose a parsimonious bipartite-cooperation model that reproduces the key features of mutualistic networks - degree distribution, nestedness and modularity -- for both ecological networks and socio-economic networks. Our analysis uses two diverse networks. Mutually-beneficial interactions between plants and their pollinators, and cooperative economic exchanges between designers and their contractors. We find that these mutualistic networks share a key hierarchical ordering of their members, along with an exponential constraint in the number and type of partners they can cooperate with. We use our model to show that slight changes in the interaction constraints can produce either extremely nested or random structures, revealing that these constraints play a key role in the evolution of mutualistic networks. This could also encourage a new systematic approach to study the functional and structural properties of networks. The surprising correspondence across mutualistic networks suggests their broadly representativeness and their potential role in the productive organization of exchange systems, both ecological and social.

This paper studies a social game where agents choose their partners as well as their actions.

Complexity, 2002

Working Papers contain accounts of scientific work of the author(s) and do not necessarily represent the views of the Santa Fe Institute. We accept papers intended for publication in peer-reviewed journals or proceedings volumes, but not papers that have already appeared in print. Except for papers by our external faculty, papers must be based on work done at SFI, inspired by an invited visit to or collaboration at SFI, or funded by an SFI grant. ©NOTICE: This working paper is included by permission of the contributing author(s) as a means to ensure timely distribution of the scholarly and technical work on a non-commercial basis. Copyright and all rights therein are maintained by the author(s). It is understood that all persons copying this information will adhere to the terms and constraints invoked by each author's copyright. These works may be reposted only with the explicit permission of the copyright holder.

Proceedings …, 2003

We develop analytical and computational models to study the conditions for the stability of a population consisting of agents with heterogeneous preferences. The analytical models that utilize an indirect evolutionary approach show that the ability to detect others' types is critical for the evolution of reciprocal preferences. The computational models of this paper incorporate agents' memories and endogenously built social networks into the evolutionary dynamics. The simulations based on the computational models show that the strength of the social network is a critical factor for the success of nonselfish preferences. A fully heterogeneous population consisting of egoists, reciprocators, and altruists can be stable for a range of parameter conditions.

2006

Journal of Public Economics, 2005

This paper reports on an experimental investigation of the evolution of networks and the individual decision making processes that guide it. Since there is no history of experimental work on network formation, part of the paper is devoted to the formulation of problems that can be examined experimentally. The results are that networks, composed of decentralized decision makers, are capable of overcoming complex coordination and learning problems and converge to stationary con…gurations. While stationarity is frequently observed, such an achievement is not guaranteed and when it doesn't occur signi…cant and persistent ine¢ciencies can result. The models of equilibration based on the principle of Nash stability are more reliable than models based on the alternative principles of e¢ciency seeking or focalness of the network con…guration. However, individual decision making within networks is not in accordance with the simple decision rule of Nash best response. Instead we observe complicated strategies that appear to trade o¤ short term pro…ts in order to signal to, and teach, other agents the strategies required for long term pro…t maximization. ¤ The …nancial support of the Laboratory of Experimental Economics and Political Science at Caltech is gratefully acknowledged.

Frontiers in physiology, 2017

We introduce a form of Self-Organized Criticality (SOC) inspired by the new generation of evolutionary game theory, which ranges from physiology to sociology. The single individuals are the nodes of a composite network, equivalent to two interacting subnetworks, one leading to strategy choices made by the individuals under the influence of the choices of their nearest neighbors and the other measuring the Prisoner's Dilemma Game payoffs of these choices. The interaction between the two networks is established by making the imitation strength K increase or decrease according to whether the last two payoffs increase or decrease upon increasing or decreasing K. Although each of these imitation strengths is selected selfishly, and independently of the others as well, the social system spontaneously evolves toward the state of cooperation. Criticality is signaled by temporal complexity, namely the occurrence of non-Poisson renewal events, the time intervals between two consecutive cr...