Papers by Guillaume Deffuant
ArXiv, 2017
This paper proposes a new method which approximates a classification function separating a $d$ di... more This paper proposes a new method which approximates a classification function separating a $d$ dimensional compact set into two parts. The approach starts by estimating the intersection between the classification boundary and the edges of a regular grid covering the compact set. Then it builds a classification surface made of recursive simplex stars (resistars) defined in the grid cubes containing such boundary points. A first variant, the simple resistar (s-resistar) defines a single star of simplices which share the barycentre of the cube boundary points and include stars of simplices defined similarly in cube facets, and so on recursively until a face boundary points define a single simplex. This definition is simple and easy to apply when the dimensionality increases. However, s-resistars sometimes "glue" together surfaces that should be separated and this deteriorates the local classification performance. The second variant, the multi-boundary resistar (or m-resistar)...
1990 IJCNN International Joint Conference on Neural Networks, 1990
Neural Computation, 1995
The perceptron membrane is a new connectionist model that aims at solving discrimination (classif... more The perceptron membrane is a new connectionist model that aims at solving discrimination (classification) problems with piecewise linear surfaces. The discrimination surfaces of perceptron membranes are defined by the union of convex polyhedrons. Starting from only one ...
European Journal of Operational Research, 1980
This paper investigates a basic model simulating empathy. The model is abstracted from recent a... more This paper investigates a basic model simulating empathy. The model is abstracted from recent advances in neurobiology, such as the discovery of mirror neurons or of neurons coding for both visual recog-nition and connected action plans. In a very simplified ...
Socionomics rely on a "copernician" move: events in society are not the cause of change... more Socionomics rely on a "copernician" move: events in society are not the cause of changes of social mood, this is the opposite. Take the Enron bankruptcy for instance. Many observers thought that the Enron scandal frightened the investors which drove the market down. But a closer ...
La these deux grandes parties. La premiere expose le cadre conceptuel dans lequel nous proposons ... more La these deux grandes parties. La premiere expose le cadre conceptuel dans lequel nous proposons de concevoir l'apprentissage et l'adaptation des systemes artificiels, illustre par la description de systemes connexionnistes standards. La deuxieme decrit un modele connexionniste nouveau, les membranes de perceptrons, inspire par le cadre conceptuel presente dans la premiere partie. Le cadre conceptuel est etabli a l'aide de deux eclairages simultanes. Le plus iomportant est celui de f. Varela, dont le point de vue de l'autonomie fournit une reference fondamentale pour les sciences de la cognition. L'autre vient des theories statistiques et probabilistes de l'apprentissage artificiel. Ce double eclairage permet d'etablir un mode de description general de l'apprentissage et de suggerer des directions possibles pour l'amelioration des systemes existants. Les membranes de perceptrons qui font l'objet de la deuixieme grande partie de ce document constituent une tentative d'amelioration de ces modeles. La structure particuliere des membranes de perceptrons leur permet d'engendrer une grande richesses de formes possibles a l'aide de composants simples (derives du perceptron). Nous etudions ensuite les differentes solutions possibles pour donner a ces objets des capacites d'adaptation passive sous l'action d'un environnement, ainsi que des dynamiques d'evolution structurelles. Ce document se termine par la presentation d'un certain nombre d'exemples de simulation effectuees sur station de travail. Les problemes abordes sont la classification automatique, l'appoximation de fonctions, et le controle de processus.
Mémoire d'habilitation à diriger des …, 2004
Ecole doctorale SPI de l'université Blaise Pascal de Clermont-Ferrand Mémoire d'Habilit... more Ecole doctorale SPI de l'université Blaise Pascal de Clermont-Ferrand Mémoire d'Habilitation à Diriger des Recherches Modéliser des systèmes complexes : quelques pistes pour relever le défi Guillaume DEFFUANT Soutenance le 3 Mars 2004 Jury : MJ Ferber MA Quilliot ...
1.1 First of all, we would like to thank the journalists, Gero von Randow, from FASZ and Isabelle... more 1.1 First of all, we would like to thank the journalists, Gero von Randow, from FASZ and Isabelle Cuchet from Courrier International for their interest in our work, as well as Klaus Troitzsch for the translation. The precise description of our model in a large audience newspaper, ...
arXiv (Cornell University), Oct 8, 2004
We consider the phenomenon of opinion shift to the extreme reported in the social psychology lite... more We consider the phenomenon of opinion shift to the extreme reported in the social psychology literature. We argue that a good candidate to model this phenomenon can be a new variant of the bounded confidence (BC) model, the smooth BC model which we propose in this paper. This model considers individuals with a continuous opinion and an uncertainty. Individuals interact by random pairs, and attract each other's opinion proportionally to a Gaussian function of the distance between their opinions. We first show that this model presents a shift to the extreme when we introduce extremists (very convinced individuals with extreme opinions) in the population, even if there is the same number of extremists located at each extreme. This behaviour is similar to the one already identified with other versions of BC model. Then we propose a modification of the smooth BC model to account for the social psychology data and theories related to this phenomenon. The modification is based on the hypothesis of perspective taking (empathy) in the context of consensus seeking.
International audienceIn the Leviathan model, agents form opinions about each other. During dyadi... more International audienceIn the Leviathan model, agents form opinions about each other. During dyadic meetings, they directly influence each other, or talk about peers through gossip. Speakers highly valued by their listeners are more influential. Moreover, they are subject to a vanity process; if an agent feels undervalued, then he decreases his opinion about the despising agent and on the contrary he increases his opinion about a compliment-giver agent. This model produces several different patterns depending on the parameter values, but the average opinion is always negative whatever the emerging pattern. As a consequence, the gossips tend to be mostly negative. Since this is not in complete accordance with the social-psychology literature indicating that both mostly negative and positive gossip can be observed, we investigate the changes to operate to obtain also mostly positive gossips. We found that when the vanity process is less triggered by agents held in low esteem, the avera...
Physica A: Statistical Mechanics and its Applications
• We aim at explaining patterns generated by an already published model in which agents discuss a... more • We aim at explaining patterns generated by an already published model in which agents discuss and modify their opinions about each other and about themselves; • We derive a mathematical approximation of the average change of the opinions for a random interaction and we assess its accuracy;
Advances in Intelligent Systems and Computing, 2017
This paper studies a simplified version of the Leviathan model, without gossip and vanity process... more This paper studies a simplified version of the Leviathan model, without gossip and vanity processes. During dyadic meetings, the agents change their opinion about themselves and about their interlocutor. Speakers highly valued by their listeners are more influential. Only due to the asymmetry of the influence function, the model produces several patterns depending on the parameter values, some of which not yet identified in the first Leviathan model study. In particular, in some cases the leaders have a high opinion of other leaders whereas in other cases they have a low one.
Edward Elgar Publishing eBooks, 2002
An agent-based model of innovation diffusion, targeted on the diffusion of agri-environmental mea... more An agent-based model of innovation diffusion, targeted on the diffusion of agri-environmental measures, is presented. An economic and static perspective on the conversion to organic farming in the French department of Allier, using data from 1996, is presented. The agent-based ...
Species can respond to climate change by tracking appropriate environmental conditions in space, ... more Species can respond to climate change by tracking appropriate environmental conditions in space, resulting in a range shift. Species Distribution Models (SDMs) can help forecast such range shift responses. For few species, both correlative and mechanistic SDMs were built, but allis shad (Alosa alosa), an endangered anadromous fish species, is one of them. The main purpose of this study was to provide a framework for joint analyses of correlative and mechanistic SDMs projections in order to strengthen conservation measures for spe-cies of conservation concern. Guidelines for joint representation and subsequent interpreta-tion of models outputs were defined and applied. The present joint analysis was based on the novel mechanistic model GR3D (Global Repositioning Dynamics of Diadromous fish Distribution) which was parameterized on allis shad and then used to predict its future distri-bution along the European Atlantic coast under different climate change scenarios (RCP 4.5 and RCP 8.5...
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Papers by Guillaume Deffuant