Denis Phan

Sorbonne University | UPMC · Groupe d’Etudes des Méthodes de l’Analyse Sociologique de la Sorbonne (GEMASS)

70 000 years ago, Homo sapiens left Africa to colonize the world. 6,000 years ago, he founded the first cities. Today, in the era of city networks, he is creating increasingly wide and complex metropolitan regions. From prehistory to the era of metropolises, man has occupied the earth's space in an infinite variety of ways, under the influence of a...

Cognitive Economics considers booth individual (cognitivist) and collective (evolutionists) point of view. Agent-Based Modeling (ABM) simulated by Multi-Agent System (MAS) allows us to integrate these two approaches. MAS is a complex interactive system, whose properties are generic: what kind of explanation can we expect from an ABM? Our argumentat...

L’économie cognitive considère les points de vue individuel (cognitiviste) et collectif (évolutionniste). La Modélisation à Base d’Agents (ABM) simulée par Système Multi-Agents (SMA) permet d’intégrer ces deux approches. Un SMA est un système complexe interactif, dont les propriétés sont génériques. Quel type d’explication attendre d’un ABM ? L’arg...

The causal power of structures in analytical sociologists’ agent-based models brings into question methodological individualism. We defend that (1) from an explanatory point of view, the syntactic properties of models require semantic conditions of interpretation drawn from a conceptual research framework; (2) in such a framework, social/relational...

The on-line English version of this Chapter is available here : https://books.openedition.org/pufr/19740 Le chapitre un dresse un bref état des différentes manières dont les « transitions » sont abordées dans la littérature, tant du point de vue des sciences de la nature que des sciences sociales. Dans ce Chapitre, les aspects théoriques ont été p...

Diversity and complementarity of multi-agent models in the social sciences Multi-agent systems have been used for fifteen years to simulate the dynamics of social phenomena. They help conceptualize interactions between an organized set of agents and to explore the structures that emerge through the formalization of complex situations where heteroge...

Multi-agent systems have been used for fifteen years to simulate the dynamics of social phenomena. They help conceptualize interactions between an organized set of agents and to explore the structures that emerge through the formalization of complex situations where heterogeneous agents operate at various levels. This paper presents and discusses a...

En philosophie, l’ontologie étudie ce qui pourrait exister : le type et la structure des objets, les propriétés, évènements, processus et relations. En ingénierie des connaissances, c’est la spécification de la conceptualisation d’un domaine de savoir. Ce domaine concerne ici la modélisation à base d’agents (ABM) pour les sciences de l’homme et de...

L'objectif de cette contribution est de montrer comment l'activité de définition d'une ontologie en vue d'une modélisation par Système Multi Agent (SMA) peut faire avancer le dialogue interdisciplinaire sur une question de sciences sociales et jeter les bases d'une comparaison systématique entre les connaissances produites par différentes disciplin...

Les marchés de biens 16.1. Introduction : ce qu'apporte la modélisation agent à l'étude des marchés Alors que le marché est l'objet d'étude central des économistes, peu d'auteurs se sont penchés sur sa définition, comme le soulignent par exemple [HOG 88] ou [AUE 90]. « Pour expliquer cette carence De Vroey [VRO 90] souligne que nombre des développe...

Dans ce chapitre, nous présentons tout d'abord quelques cadres conceptuels pour aborder la question du marché. Ceux-ci proviennent principalement, mais non exclusivement du discours des économistes. Il s'agit en particulier d'introduire des points de vue qui permettent de fournir des descriptions positives des échanges marchands dans leur environne...

In this article, we briefly review the models of social interactions concerning the pricing of goods with Bandwagon properties.

Whenever customers' choices (e.g. to buy or not a given good) depend on others choices (cases coined 'positive externalities' or 'bandwagon effect' in the economic literature), the demand may be multiply valued: for a same posted price, there is either a small number of buyers, or a large one -- in which case one says that the customers coordinate....

Descrição Os textos dessa densa obra, escritos por autores nacionais e do exterior, vêm dar fôlego ao campo interdisciplinar e moderno das ciências cognitivas e da filosofia da mente na discussão sobre o tema da representação mental. Tema central da psicologia cognitiva, a representação constitui-se, nos dias de hoje, numa área fronteiriça, inquie...

Résumé En philosophie, l’ontologie est « la science de ce qui est, des types et structures des objets, propriétés, évènements, processus et relations »; En informatique et management des connaissances, une « ontologie » est la spécification de la conceptualisation d’un domaine de connaissance. Pour la simulation multi-agents, le domaine concerne le...

Now that complex Agent-Based Models and computer simulations spread over economics and social sciences - as in most sciences of complex systems -, epistemological puzzles (re)emerge. We introduce new epistemological concepts so as to show to what extent authors are right when they focus on some empirical, instrumental or conceptual significance of...

Agent-Based Models are useful to describe and understand social, economic and spatial systems\' dynamics. But, beside the facilities which this methodology offers, evaluation and comparison of simulation models are sometimes problematic. A rigorous conceptual frame needs to be developed. This is in order to ensure the coherence in the chain linking...

Now that complex Agent-Based Models and computer simulations spread over economics and social sciences - as in most sciences of complex systems -, epistemological puzzles (re)emerge. We introduce new epistemological concepts so as to show to what extent authors are right when they focus on some empirical, instrumental or conceptual significance of...

Moduleco is a "multi-agent" platform, at the crossroads between several disciplines, designed to simulate markets and organisations, social phenomenon and population dynamics. Multi-agent systems are popular in computing science and within the domain of artificial intelligence. Generally, the Agent is defined as referring to a software component wh...

We consider a model of socially interacting individuals that make a binary choice in a context of positive additive endogenous externalities. It encompasses as particular cases several models from the sociology and economics literature. We extend previous results to the case of a general distribution of idiosyncratic preferences, called here Idiosy...

This paper summarizes the effects of social influences in a monopoly market with heterogeneous agents. The market equilibria are presented in the limiting case of global influence. Considering static profit maximization there may exist two different regimes: to sell either to a large fraction of customers at a low price, or to a small fraction of t...

Now that complex Agent-Based Models and computer simulations spread over economics and social sciences-as in most sciences of complex systems-, epistemological puzzles (re)emerge. We introduce new epistemological tools so as to show to what precise extent each author is right when he focuses on some empirical, instrumental or conceptual significanc...

This chapter provides a critical survey of emergence definitions both from a conceptual and formal standpoint. The notions of downward / backward causation and weak / strong emergence are specially discussed, for application to complex social system with cognitive agents. Particular attention is devoted to the formal definitions introduced by (Müll...

The aim of this paper is to stress some ontological and methodological issues for Agent-Based Model (ABM) building, exploration, and evaluation in the Social and Human Sciences. Two particular domain of interest are to compare ABM and simulations (Model To Model) within a given academic field or across different disciplines and to use ontology for...

In this paper we explore the impact of social influence on the equilibria in the simplest model with binary choices. We investigate the interplay between the social influence and individual decision to adopt with global interactions, both analytically in the case of an infinite number and numerically in the case of a finite number of agents. We der...

This chapter provides a critical survey of emergence definitions both from a conceptual and formal standpoint. The notions of downward/backward causation and weak/strong emergence are specially discussed for application to complex social system with cognitive agents. Particular attention is devoted to the formal definitions introduced by Müller (20...

Appendix 1 - Epistemology in a Nutshell: Theory, Model, Simulation and Experiment - Denis Phan, Anne-Françoise Schmid and Franck Varenne

This volume brings together contributions from leading researchers in the field of agent-based modelling and simulation. This approach has grown out of some recent and innovative ideas in the social sciences, computer sciences, life sciences, physics and game theory. It is proving helpful in understanding complexity in many domains. The opportuniti...

We consider a model of socially interacting individuals that make a binary choice in a context of positive additive endogenous externalities. It encompasses as particular cases several models from the sociology and economics literature. We extend previous results to the case of a general distribution of idiosyncratic preferences, called here Idiosy...

In this paper we explore numerically by means of ACE the impact of local social influence on binary choices. The basic model of binary choices with externality presented here (the “GNP model”) is based on Gordon et al. (2005); Nadal et al. (2005); Phan and Pajot (2006) (see Phan and Semeshenko (2007) for an introduction and a review of literature)....

We consider a simple model in which a population of individuals with idiosyncratic willingnesses to pay must choose repeatedly either to buy or not a unit of a single homogeneous good at a given price. Utilities of buyers have positive externalities due to social interactions among customers. If the latter are strong enough, the system has multiple...

The present paper discusses implications for Agent-based Computational Economics (ACE) of a formal definition of emergence introduced by Dessalles, Phan in part I of this work. This exemplification is based on an extension of the model of emergence of classes by Axtell et al. The present paper is an attempt to integrate both downward and upward cau...

This paper illustrates the effects of global or local social influences upon binary choice. Analytical results are summarized and an ACE (Agent based Computational Economics) approach is used to investigate the corresponding mechanisms of interdependence in the case of a coordination problem and finite size effects.

Résumé de Modélisation et simulation multi-agents : applications... La modélisation multi-agents permet de conceptualiser et de simuler un ensemble organisé d'agents en interaction entre eux et avec leur environnement. Dans les Sciences de l'Homme et de la Société (SHS), elle permet de formaliser des situations complexes comportant des échelles (s...

La modélisation multi-agents permet de conceptualiser et de simuler un ensemble organisé d'agents en interaction entre eux et avec leur environnement. Dans les Sciences de l'homme et de la société, elle permet de formaliser des situations complexes comportant des échelles (spatiales, temporelles, organisationnelles) miltiples et des agents hétérogè...

This paper provides a formal definition of emergence, operative in multi-agent framework and which make sense from both a cognitive and an economics point of view. The first part discuses the ontological and epistemic dimension of emergence and provides a complementary set of definitions. Following Bonabeau, Dessalles, emergence is defined as an un...

We explore the effects of social influence in a simple market model in which a large number of agents face a binary choice: to buy/not to buy a single unit of a product at a price posted by a single seller (monopoly market). We consider the case of positive externalities: an agent is more willing to buy if other agents make the same decision. We co...

In this paper, we consider a discrete choice model where heterogeneous agents are subject to mutual influences. We explore some consequences on the market's behaviour, in the simplest case of a uniform willingness to pay distribution. We exhibit a first-order phase transition in the profit optimization by the monopolist: if the social influence is...

We study social organizations with possible coexistence at equilibrium of cooperating individuals and pure consumers (free-riders). We investigate this polymorphic equilibrium using a game-theoretic approach and a statistical physics analysis of a simple model. The agents face a binary decision problem: whether to contribute or not to the public go...

This paper provides a short introduction to Agent-based Computational Economics (ACE), in order to underline the interest of such an approach in cognitive economics. Section 2 provides a brief bird's eye view of ACE. In section 3, some interesting features of the Santa-Fe Approach to complexity are then introduced by taking simple examples using th...

This Chapter extends some economic models that take advantage of a formalism inspired from statistical mechanics to account for social inuence in individual decisions. Starting with a framework suggested by Durlauf, Blume and Brock, we introduce three classes of models shifting progressively from rational towards adaptive expectations. We discuss t...

This Chapter provides a short introduction to Agent-based Computational Economics (ACE), in order to underline the interest of such an approach in cognitive economics. Section 22.2 provides a brief bird’s eye view of ACE. In section 22.3, some interesting features of the Santa-Fe Approach to complexity are then introduced by taking simple examples...

We use panel data from the National Longitudinal Survey of Youth (NLSY) to examine how body weight changes with age for a cohort moving through early adulthood, to investigate how the age-obesity gradient differs with socioeconomic status (SES) and to study channels for these SES disparities. Our results show first that weight increases with age an...

In this paper, we explore the effects of localised externalities introduced through interaction structures upon the properties of the simplest market model: the discrete choice model with a single homogeneous product and a single seller (the monopoly case). The resulting market is viewed as a complex interactive system with a communication network....

We use panel data from the National Longitudinal Survey of Youth (NLSY) to examine how body weight changes with age for a cohort moving through early adulthood, to investigate how the age-obesity gradient differs with socioeconomic status (SES) and to study channels for these SES disparities. Our results show first that weight increases with age an...

La thèse s'organise autour d'une mise en perspective de travaux " d'économie historique appliquée " publiés ou présentés dans les dix dernières années : six articles publiés dans des revues à comité de lectures, des contribution à des ouvrages collectifs et travaux d'édition, un livre sur l'économie des télécommunications et de l'Internet et divers...

Les logiciels dits "libres" suscitent actuellement un intérêt certain. Les sources de ce succès peuvent être rattachées en particulier aux caractéristiques économiques du logiciel, d'une part, et à l’évolution structurelle de l'industrie informatique, d'autre part. Du point de vue économique, le logiciel possède certains des attributs qui caractéri...

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La notion de service universel pose les questions des fondements économiques s'y rattachant et de son incompatibilité éventuelle avec la notion de service public. L'article commence par examiner l'historique de la notion de service universel (aux États-Unis et au sein de l'Union Européenne) en soulignant les conditions totalement différentes qui on...

Armelle BEUNARDEAU, Denis PHAN, Dix ans de liberalisation des services de telecommunications au Royaume-Uni : un tour d'horizon des changements institutionnels. Les transformations institutionnelles brittaniques comportent deux aspects, dont la logique economique presente quelques elements contradictoires : la volonte affirmee de promouvoir la conc...

The study of Renault's management between the two World Wars point out the following facts: the capital accumulation and growth of sales were limited by a lack of profitability and existing outlets for its range of products. Since 1930, a new resilience to a drop in nominal wages gave a major influence to profit fluctuations towards a trend for pro...

This paper deals with the modeling of the social dimension of artificial societies with cognitive agents. We provide a critical review of the ontological status of collective beliefs in some recent works in game theory, using a heuristic diagrammatic framework, useful for MAS design, called the "4Quadrant". We introduce first a formal presentation...

In this paper, we explore the effects of the introduction of localised externalities through interaction structures upon local and global properties of the simplest mar-ket model: the discrete choice model with a single homogeneous product and a single seller (monopoly). Following Kirman, the resulting market is viewed as a complex interactive syst...

This paper underlines how Object Oriented Programming (OOP) used within an agent-based framework allows one to make explicit in a specific design pattern the cognitive hierarchy between types of agents and makes a family of a model tractable both for programming and for semantic purposes. We also discuss the transposition of tools, methods and conc...

KEYWORDS Agent based computational economics, interaction network structures, critical threshold, symmetry breaking and phase transition, small world, evolutionary games, monopoly market with discrete choice and local externality. ABSTRACT This paper reviews some aspects of complex collective behaviour in an agent-based framework. It examines the e...