On Non-Bayesian Social Learning

We study a model of information aggregation and social learning recently proposed by Jadbabaie, Sandroni, and Tahbaz-Salehi, in which individual agents try to learn a correct state of the world by iteratively updating their beliefs using private observations and beliefs of their neighbors. No individual agent's private signal might be informative enough to reveal the unknown state. As a result, agents share their beliefs with others in their social neighborhood to learn from each other. At every time step each agent receives a private signal, and computes a Bayesian posterior as an intermediate belief. The intermediate belief is then averaged with the belief of neighbors to form the individual's belief at next time step. We find a set of minimal sufficient conditions under which the agents will learn the unknown state and reach consensus on their beliefs without any assumption on the private signal structure. The key enabler is a result that shows that using this update, agents will eventually forecast the indefinite future correctly

Distributed Learning from Interactions in Social Networks

We consider a network scenario in which agents can evaluate each other according to a score graph that models some interactions. The goal is to design a distributed protocol, run by the agents, that allows them to learn their unknown state among a finite set of possible values. We propose a Bayesian framework in which scores and states are associated to probabilistic events with unknown parameters and hyperparameters, respectively. We show that each agent can learn its state by means of a local Bayesian classifier and a (centralized) Maximum-Likelihood (ML) estimator of parameter-hyperparameter that combines plain ML and Empirical Bayes approaches. By using tools from graphical models, which allow us to gain insight on conditional dependencies of scores and states, we provide a relaxed probabilistic model that ultimately leads to a parameter-hyperparameter estimator amenable to distributed computation. To highlight the appropriateness of the proposed relaxation, we demonstrate the distributed estimators on a social interaction set-up for user profiling.Comment: This submission is a shorter work (for conference publication) of a more comprehensive paper, already submitted as arXiv:1706.04081 (under review for journal publication). In this short submission only one social set-up is considered and only one of the relaxed estimators is proposed. Moreover, the exhaustive analysis, carried out in the longer manuscript, is completely missing in this versio

Influence of sports drink taste preference on consumption in adult recreational soccer players

Sports drinks provide nutrients that improve athletic performance. This study investigated whether a preference in taste leads to an increased consumption of a sports drink prior to and after an endurance event in athletes. Male amateur soccer players (n=16) first participated in a blind sensory evaluation to determine their taste preference for two (designated as Drink A and Drink B) similarly flavored sports drinks. Subjects were divided into two groups based on their taste preference for either drink. They then participated in 9 soccer matches and were presented with either Drink A, Drink B, or water (3 trials each) before and after matches. Volumes of drinks voluntarily consumed were measured and averaged. Both groups consumed similar amounts of either Drink A or Drink B, before and after matches. Taste preference for a drink did not influence the amount of a sports drink that athletes consumed pre- or post- exercise

Essays on Learning in Social Networks

Over the past few years, online social networks have become nearly ubiquitous, reshaping our social interactions as in no other point in history. The preeminent aspect of this social media revolution is arguably an almost complete transformation of the ways in which we acquire, process, store, and use information. In view of the evolving nature of social networks and their increasing complexity, development of formal models of social learning is imperative for a better understanding of the role of social networks in phenomena such as opinion formation, information aggregation, and coordination. This thesis takes a step in this direction by introducing and analyzing novel models of learning and coordination over networks. In particular, we provide answers to the following questions regarding a group of individuals who interact over a social network: 1) Do repeated communications between individuals with different subjective beliefs and pieces of information about a common true state lead them to eventually reach an agreement? 2) Do the individuals efficiently aggregate through their social interactions the information that is dispersed throughout the society? 3) And if so, how long does it take the individuals to aggregate the dispersed information and reach an agreement? This thesis provides answers to these questions given three different assumptions on the individuals\u27 behavior in response to new information. We start by studying the behavior of a group of individuals who are fully rational and are only concerned with discovering the truth. We show that communications between rational individuals with access to complementary pieces of information eventually direct everyone to discover the truth. Yet in spite of its axiomatic appeal, fully rational agent behavior may not be a realistic assumption when dealing with large societies and complex networks due to the extreme computational complexity of Bayesian inference. Motivated by this observation, we next explore the implications of bounded rationality by introducing biases in the way agents interpret the opinions of others while at the same time maintaining the assumption that agents interpret their private observations rationally. Our analysis yields the result that when faced with overwhelming evidence in favor of the truth even biased agents will eventually learn to discover the truth. We further show that the rate of learning has a simple analytical characterization in terms of the relative entropy of agents\u27 signal structures and their eigenvector centralities and use the characterization to perform comparative analysis. Finally, in the last chapter of the thesis, we introduce and analyze a novel model of opinion formation in which agents not only seek to discover the truth but also have the tendency to act in conformity with the rest of the population. Preference for conformity is relevant in scenarios ranging from participation in popular movements and following fads to trading in stock market. We argue that myopic agents who value conformity do not necessarily fully aggregate the dispersed information; nonetheless, we prove that examples of the failure of information aggregation are rare in a precise sense

Bayesian Quadratic Network Game Filters

A repeated network game where agents have quadratic utilities that depend on information externalities -- an unknown underlying state -- as well as payoff externalities -- the actions of all other agents in the network -- is considered. Agents play Bayesian Nash Equilibrium strategies with respect to their beliefs on the state of the world and the actions of all other nodes in the network. These beliefs are refined over subsequent stages based on the observed actions of neighboring peers. This paper introduces the Quadratic Network Game (QNG) filter that agents can run locally to update their beliefs, select corresponding optimal actions, and eventually learn a sufficient statistic of the network's state. The QNG filter is demonstrated on a Cournot market competition game and a coordination game to implement navigation of an autonomous team

An assessment of the political will for oil and gas privatisation in Iran.

This study explores issues surrounding the potential for the privatisation of some of Iran’s national institutions. In particular, it addresses the issue of what the determinants of the Iranian policy of privatisation are, in order to ascertain whether there is the political will to privatise the Iranian oil and gas industry. In order to answer this question, this study takes a three-pronged approach which relies on multiple methodologies. It begins by providing a theoretical basis for the determination of privatisation policy. Subsequently, it explores a set of international precedents that bind the possibilities of privatisation policy. It then presents an historical outlook on Iran since World War II in order to build a context for the determinants of privatisation policy in Iran. This historical analysis is based on a political economy framework. Finally, the specific background, legal and institutional framework, and policy-maker perspectives are incorporated into the overall analysis. In this final section, particular attention is paid to the views of Iranian policy-makers that have been gained through personal interviews and questionnaires. Together, these three approaches provide a cumulative understanding of the determinants of privatisation policy in Iran. Based on this general assessment, the study makes specific appraisals of the political will of Iranian policy-makers to privatise the oil and gas industry

Financiamiento de terceros en arbitraje internacional en Irán

The present research focuses on arbitration, which seeks to examine the advantages and disadvantages of third party funding(TPF) and its differences with other forms of financial interference and determines who can act as an investor. The result of this research is that third party funding has disadvantages and advantages that in general, its advantages are dominated due to the difference in volume of funding, and investors in this area can be lawyers, insurance companies or any other person who is not prohibited by law and can be simulated and executed under the Article 10 of civil law.La presente investigación se centra en el arbitraje, que busca examinar las ventajas y desventajas del financiamiento de terceros (TPF) y sus diferencias con otras formas de interferencia financiera y determina quién puede actuar como inversionista. El resultado de esta investigación es que la financiación de terceros tiene desventajas y ventajas que, en general, sus ventajas están dominadas debido a la diferencia en el volumen de financiación, y los inversores en esta área pueden ser abogados, compañías de seguros o cualquier otra persona que no esté prohibida. por ley y puede simularse y ejecutarse de conformidad con el artículo 10 del derecho civil

A Critical Analysis of Lighting and llumination of the Central District of Tehran

This article tries to survey and criticize the quality of lighting and illumination in the central district of Tehran, by comparing it to standard codes. Findings report that the traffic lighting is standard, but illumination of sidewalks and pedestrian areas and cycle paths has many problems. Most of the important buildings of the district are not illuminated properly and lighting them according to their masses and architectural features is needed. In conclusion it has been resulted that there is a distinct need to a master plan for public lighting which, apart from defining general concepts, often put forward designs for specific urban districts and unifies light design in them.This article tries to survey and criticize the quality of lighting and illumination in the central district of Tehran, by comparing it to standard codes. Findings report that the traffic lighting is standard, but illumination of sidewalks and pedestrian areas and cycle paths has many problems. Most of the important buildings of the district are not illuminated properly and lighting them according to their masses and architectural features is needed. In conclusion it has been resulted that there is a distinct need to a master plan for public lighting which, apart from defining general concepts, often put forward designs for specific urban districts and unifies light design in them