Guillaume Deffuant

• Senior researcher (DR1)
• French National Institute for Agriculture, Food, and Environment (INRAE)

The paper relates virtual dialogues about social simulation, with the implicit reference to Galieo\'s \'dialogues concerning two new sciences\'.

We propose an opinion dynamics model that combines processes of vanity and opinion propagation. The interactions take place between randomly chosen pairs. During an interaction, the agents propagate their opinions about themselves and about other people they know. Moreover, each individual is subject to vanity: if her interlocutor seems to value he...

This chapter studies continuous opinion models with extremists, and we use probability distribution models which approximate the behaviour of agents based models in order to explain their attractor patterns. The probability distribution is defined on a discrete grid in the opinion / uncertainty space. We compute the equations of probability flows b...

Resilience, the capacity for a system to recover from a perturbation so as to keep its properties and functions, is of growing concern to a wide range of environmental systems. The challenge is often to render this concept operational without betraying it, nor diluting its content. The focus here is on building on the viability theory framework of...

We consider a recent model in which agents hold opinions about each other and influence each other’s opinions during random pair interactions. When the opinions are initially close, on the short term, all the opinions tend to increase over time. On the contrary, when the opinions are initially very unequal, the opinions about agents of high status...

This paper studies the bounded confidence model on growing fully-mixed populations. In this model, in addition to the usual opinion clusters, significant secondary clusters of smaller size appear systematically, while those secondary clusters appear erratically and include much fewer agents when the population is fixed. Through simulations, we deri...

Energy dependence is a very important issue on the energy agenda of the Baltic states. The shortage of electric energy has been affected by several factors, which began with the Chernobyl disaster, the closure of Ignalina, and the suspension of the Visagina project. Decisions have been influenced by political situations involving other neighboring...

The bounded confidence model assumes simple continuous opinion dynamics in which agents ignore opinions which are too far from their own. The two initial variants—Hegselmann–Krause (HK) and Deffuant–Weisbuch (DW)—of the model have attracted significant attention since the early 2000s. This paper revisits the version of the HK model applied to a pro...

The widely observed positive bias on self-evaluation is mainly explained by the self-enhancement motivation which minimizes negative feedbacks and emphasizes positive ones. Recent agent based simulations suggest that a positive bias also emerges if the sensitivity to feedbacks decreases when the self-evaluation increases. This paper proposes a simp...

We study the bounded confidence model on a growing population. We compare simulations of the agent model, its version in continuous densities and with the standard influence function or a smoother influence function. We find that the model on a growing population generates bigger secondary clusters and more systematically than when the population i...

Worry over polarization has grown alongside the digital information consumption revolution. Where most scientific work considered user-generated and user-disseminated (i.e.,~Web 2.0) content as the culprit, the potential of purely increased access to information (or Web 1.0) has been largely overlooked. Here, we suggest that the shift to Web 1.0 al...

We consider an opinion dynamics model where, during random pair interactions, each agent modifies her opinions about both agents of the random pair and also about some other agents, chosen randomly. Moreover, each agent belongs to a single group and the opinions within the group are attracted to their average. In simulations starting from neutral o...

In two studies about farming practices, the respondents who are particularly favorable to organic farming tend to have a higher intention to convert their farm to organic when they perceive other farmers as not very favorable to this practice. This intention can be considered as anticonformist, as it is in opposition to the general view of others....

Risks of drought complicate decision-making in grass-based livestock systems. Here, we assessed the pertinence of the stochastic viability framework (SV) for making relevant decisions in a system exposed to climate shocks. SV involves maximizing the probability of satisfying predefined constraints over time through adapted decision-making. We appli...

The framework Topology of Sustainable Management by Heitzig et al. (Earth Syst Dyn 7:21. https://doi.org/10.5194/esd-7-21-2016, 2016) distinguishes qualitatively different regions in state space of dynamical models representing manageable systems with default dynamics. In this paper, we connect the framework to viability theory by defining its main...

We consider a recent model in which agents hold opinions about each other and influence each other's opinions during random pair interactions. When the opinions are initially close, on the short term, all the opinions tend to increase over time. On the contrary, when the opinions are initially very unequal, the opinions about agents of high status...

Attitudes and social norms are key social psychological concepts that have often been considered as independent determinants of human behavior. However, questions about the interplay between the two are somewhat of a blind spot in social psychology. In the present research, we test the hypothesis that when an important change in norms is involved,...

Abstract Integrated assessment models (IAMs) are commonly used by decision makers in order to derive climate policies. IAMs are currently based on climate‐economics interactions, whereas the role of social system has been highlighted to be of prime importance on the implementation of climate policies. Beyond existing IAMs, we argue that it is there...

We propose an agent-based model leading to a decrease or an increase of hostility between agents after a major cultural threat such as a terrorist attack. The model is inspired from the Terror Management Theory and the Social Judgement Theory. An agent has a cultural identity defined through its acceptance segments about each of three different cul...

“Original survey script”. (PDF)

“Code book of the survey”. (PDF)

This is a text file which can be opened as a table, or a csv file. The variables are: identifier of the participant, region of France, age, gender, attitude toward Christians, attitude toward Muslims, attitude toward areligious, religion, religion (others), time of beginning of the survey, time of end of the survey. (TXT)

One Health (OH), EcoHealth (EH), and Planetary Health (PH) share an interest in transdisciplinary efforts that bring together scientists, citizens, government and private sectors to implement contextualized actions that promote adaptive health management across human, animal and ecosystem interfaces. A key operational element underlying these Integ...

The Intergovernmental Panel on Climate Change anticipates increasing extreme rain events in the 21st century, leading to more frequent floods and more phosphorus transported into lakes, enhancing the risk of their eutrophication. This paper reports research assessing this risk on Lake Bourget in France, by coupling a statistical estimation of annua...

We consider a simple model of agents modifying their opinion about themselves and about the others during random pair interactions. Two unexpected patterns emerge: (1) without gossips, starting from zero, agents' opinions tend to grow and stabilize on average at a positive value; (2) when introducing gossips, this pattern is inverted; the opinions...

Bitcoin-otc is a peer to peer, over-the-counter marketplace for trading with bitcoin crypto-currency. To mitigate the risks of the unsupervised exchanges, the establishment of a reliable reputation systems is needed: for this reason, a web of trust is implemented on the website. The availability of all the historic of the users interaction data mak...

We aim to study through an agent-based model the cultural conditions leading to a decrease or an increase of discrimination between groups after a major cultural threat such as a terrorist attack. We propose an agent-based model of cultural dynamics inspired from the social psychological theories. An agent has a cultural identity comprised of the m...

Bitcoin-otc is a peer to peer (over-the-counter) marketplace for trading with bit- coin crypto-currency. To mitigate the risks of the p2p unsupervised exchanges, the establishment of a reliable reputation systems is needed: for this reason, a web of trust is implemented on the website. The availability of all the historic of the users interaction d...

1 Abstract This study aims to better understand why farmers do not convert to organic farming by studying decision trajectories in a dynamic agent‐based model. In this model, an agent's decision on transitioning to organic is based on the comparison between satisfaction with its current situation and potential satisfaction with an alternative farmi...

Questions Many Western European and North American countries are experiencing a strong reforestation since two centuries due to agricultural abandonment. Other land use changes, such as urbanization, can simultaneously trigger forest erosion. In this context of habitat turnover, forest understorey plant dynamics depends on the balance between immig...

Previous analyses of the regional distribution of forest plants have revealed that some species have a biased distribution towards either ancient or recent forest patches. It has been therefore proposed to classify forest plant species according to their affinity for ancient or recent patches. In this contribution, we aimed at providing a dynamical...

In 1997, Robert Axelrod wondered in a highly influential paper “If people tend to become more alike in their beliefs, attitudes, and behavior when they interact, why do not all such differences eventually disappear?” Axelrod’s question highlighted an ongoing quest for formal theoretical answers joined by researchers from a wide range of disciplines...

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 star...

In order to define a paradigm of sustainability for human development and our co-evolution with the earth system, Rockstr\"om et al. [58] introduced Planetary boundaries with superseding refinements by Steffen et al. [66]. They are a set of planetary-scale thresholds whose transgression may be catastrophic for the earth system. The question of thei...

We propose a hybrid microsimulation and agent-based model of mobility integrating migration and residential mobility. We tested it on the evolution of the population of the Cantal, a French “département” with 150,000 inhabitants. We calibrated it using various data sources from 1990 to 2006, and tested its predictions on other data of the same peri...

This chapter studies a model of agents having an opinion about each other agent and about themselves. During dyadic meetings, the agents change their opinion about themselves and about their interlocutor in the direction of a noisy perception of the opinions of their interlocutor. Moreover highly valued agents are more influential. This model produ...

Using the bounded-confidence model, with fixed uncertainties and extremists, we investigate how resilient the moderate mean opinion of a population is to the arrival in it of a new group of agents, when the energy of the opinion of this group (extremeness × group size) is varied. We say moderate mean opinion is resilient when, even though it may be...

We propose a hybrid microsimulation and agent-based model of mobility integrating migration and residential mobility. We tested it on the evolution of the population of the Cantal, a French “département” with 150,000 inhabitants. We calibrated it using various data sources from 1990 to 2006, and tested its predictions on other data of the same peri...

This paper studies a model of agents having an opinion about each other agent and about themselves. During dyadic meetings, the agents change their opinion about themselves and about their interlocutor in the direction of a noisy perception of the opinions of their interlocutor. Moreover highly valued agents are more influential. This model produce...

Time-variant reliability analysis aims at assessing the probability of failure of a time-variant system within a given time horizon. We illustrate in this paper the computation of the reliability kernel which is the set of initial states for which the probability of failure remains under a threshold within the considered time horizon. This paper su...

Computing a viability kernel consumes time and memory resources which increase exponentially with the dimension of the problem. This curse of dimensionality strongly limits the applicability of this approach, otherwise promising. We report here an attempt to tackle this problem with Graphics Processing Units (GPU). We design and implement a version...

Community dynamics is influenced by multiple ecological processes such as environmental spatiotemporal variation, competition between individuals and demographic stochasticity. Quantifying the respective influence of these various processes and making predictions on community dynamics require the use of a dynamical framework encompassing these vari...

The bounded confidence model and its variants applied to moderate and extremist agents exhibit three types of attractors: central clusters, double extreme and single extreme clusters. These attractors are observed when the models include a dynamics on the uncertainties tending to decrease the moderate uncertainties when interacting with extremists....

This work proposes to address a lack of conceptual consensus surrounding the concept of vulnerability, by fostering a minimal definition as a measure of potential future harm, and by basing it on a stochastic controlled dynamical system framework. Harm is defined as a normative judgment on a trajectory. Considering all the possible trajectories fro...

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 o...

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 pa...

We propose an hybrid microsimulation and agent-based model of mobility integrating migration and residential mobility. We tested it on the evolution of the population of the Cantal, a French " département " with 150,000 inhabitants. We calibrated it using various data sources from 1990 to 2006, and tested its predictions on other data of the same p...

Nous distinguons trois visions de la complexité afin de clarifier les contours de la recherche dans ce domaine. Nous utilisons le démon de Laplace comme référence pour présenter ces visions. La vision 1 brise le rêve du démon de Laplace en identifiant des systèmes particuliers qui lui résistent en mathématiques, physique et informatique. La vision...

In this paper we propose a modern version of Laplace’s Demon that helps us unfold the notion of complexity into three visions revealing axes of difference and complementarity. The first vision concerns systems in mathematics, logics and physics which overthrow the illusion of past forms of predictability while opening the way to new concepts such a...

The goal of this paper is twofold: (1) to show that time-variant reliability and a branch of control theory called stochastic viability address similar problems with different points of view, and (2) to demonstrate the relevance of concepts and methods from stochastic viability in reliability problems.nOn the one hand, reliability aims at evaluatin...

Background and Aims Simple models of herbaceous plant growth based on optimal partitioning theory predict, at steady state, an isometric relationship between shoot and root biomass during plant ontogeny, i.e. a constant root–shoot ratio. This prediction has received mixed empirical support, suggesting either that optimal partitioning is too coarse...

Within the context of ongoing environmental changes, the life history of diadromous fish represents a real potential for exploring and colonizing new environments due to high potential dispersal abilities. The use of dynamic approaches to assess how these species will respond to climate change is a challenging issue and mechanistic models able to i...

During the PRIMA European project, we conceived a conceptual model dedicated to the study of the evolution of the European Rural Areas in terms of demography and occupation of their populations. This is a hybrid agent-microsimulation model considering inhabitants as the basic elements composing in households. On the other hand, municipalities are t...

We compare a sample-free method proposed by Gargiulo et al. (2010) and a sample-based method proposed by Ye et al. (2009) for generating a synthetic population, organised in households, from various statistics. We generate a reference population for a French region including 1310 municipalities and measure how both methods approximate it from a set...

The increasing integration of technology into our lives has created unprecedented volumes of data on society's everyday behaviour. Such data opens up exciting new opportunities to work towards a quantitative understanding of our complex social systems, within the realms of a new discipline known as Computational Social Science. Against a background...

During the PRIMA European project, we conceived a conceptual model dedicated to the study of the evolution of the European Rural Areas in terms of demography and occupation of their populations. This is a hybrid agent-microsimulation model considering inhabitants as the basic elements composing in households. On the other hand, municipalities are t...

We address the performance of an aquifer system where water is extracted at a given baseline pumping rate under the following conditions: 1) catastrophic events such as saltwater intrusion or pollution can interrupt water extraction, 2) recharge is a stochastic process, and 3) the possibility of management to reduce the pumping rate if necessary is...

A knowledge of the mechanical properties of bacterial biofilms is required to more fully understand the processes of biofilm formation such as initial adhesion or detachment. The main contribution of this paper is to demonstrate the use of homogenization techniques to compute mechanical parameters of Pseudomonas aeruginosa PAO1 biofilms. For this p...

We present a simple stochastic model of lake eutrophication to demonstrate how the mathematical framework of viability theory fosters operational definitions of resilience, vulnerability and adaptive capacity, and then helps understand which response one should bring to environmental changes. The model represents the phosphorus dynamics, given that...

This deals with the response of a coupled human and natural system (CHANS) to a natural hazard by using the concepts of resilience and vulnerability within the mathematical framework of viability theory. This theory applies to time-evolving systems such as CHANS and assumes that their desirable properties can be defined as a subset of their state s...

Meadows and Cliff (2012) failed to replicate the results of Deffuant et al. (2002) and concluded that our paper was wrong. In this note, we show that the conclusions of Meadows and Cliff are due to a wrong computation of indicator y, which was not fully specified in our 2002 paper. In particular, Meadows and Cliff compute indicator y before model c...

In this paper the authors present a semi-automatic method for designing and generating spatial data cubes in order to visualize and analyze the results of simulation models. In the authors approach users choose their fact of analysis, then the system derives automatically a set of possible measures, dimensions of analysis, and generates the corresp...

Nous décrivons un modèle de dynamique d’opinions dans lequel les agents se rencontrent deux à deux de manière aléatoire et font évoluer les opinions qu’ils ont les uns des autres par des mécanismes de vanité et de propagation. Les simulations révèlent une grande richesse de comportements du modèle lorsque les paramètres varient. Nous avons identifi...

Nous décrivons un modèle de dynamique d’opinions dans lequel les agents se rencontrent deux à deux de manière aléatoire et font évoluer les opinions qu’ils ont les uns des autres par des mécanismes de vanité et de propagation. Les simulations révèlent une grande richesse de comportements du modèle lorsque les paramètres varient. Nous avons identifi...

We propose an opinion dynamics model that combines processes of vanity and opinion propagation. The interactions take place between randomly chosen pairs. During an interaction, the agents propagate their opinions about themselves and about other people they know. Moreover, each individual is subject to vanity: if her interlocutor seems to value he...

This position paper proposes a vision for the research activity about sustainability in global environmental change (GEC) taking place in the FuturICT flagship project. This activity will be organised in an “Exploratory”, gathering a core network of European scientists from ICT, social simulation, complex systems, economics, demographics, Earth sys...

The increasing integration of technology into our lives has created unprecedented volumes of data on society’s everyday behaviour. Such data opens up exciting new opportunities to work towards a quantitative understanding of our complex social systems, within the realms of a new discipline known as Computational Social Science. Against a background...

We show that a recently proposed model generates accurate commuting networks on 80 case studies from different regions of the world (Europe and United-States) at different scales (e.g. municipalities, counties, regions). The model takes as input the number of commuters coming in and out of each geographic unit and generates the matrix of commuting...

(ZIP)

The main contribution of this paper is to use homogenization techniques to compute diffusion coefficients from experimental images of microbial biofilms. Our approach requires the analysis of several experimental spatial structures of biofilms in order to derive from them a Representative Volume Element (RVE). Then, we apply a suitable numerical pr...

We use a minimum requirement approach to derive the number of jobs in proximity services per inhabitant in French rural municipalities. We first classify the municipalities according to their time distance to the municipality where the inhabitants go the most frequently to get services (called MFM). For each set corresponding to a range of time dis...

This paper examines the multidimensional modeling of a data warehouse for simulation results. Environmental dynamics modeling is used to study complex scenarios like urbanization, climate change and deforestation while allowing decision makers to understand and predict the evolution of the environment in response to potential value changes in a lar...

This article describes Simexplorer, a computer framework for managing simulation experiments and, to some extent, the scientific quality of the modelling process. An information system, included in the framework, insures the traceability of the experiments and their reproducibility and thus contributes to the modelling process quality management. M...

This paper explores the dynamics of attitude change in two dimensions resulting from social interaction. We add a rejection mechanism into the 2D bounded confidence (BC) model proposed by Deffuant et al. (2001). Individuals are characterized by two-dimensional continuous attitudes, each associated with an uncertainty u, supposed constant in this fi...

Approximate Bayesian computation (ABC) is a family of computational techniques in Bayesian statistics. These techniques allow to fi t a model to data without relying on the computation of the model likelihood. They instead require to simulate a large number of times the model to be fi tted. A number of re finements to the original rejection-based A...

In many industrial applications, bacteria are cultivated in mixed bioreactors filled with water and fed with nutrients. Depending on the reactor configuration and operating conditions, bacteria can either be grown as planktonic freely floating cells or attached to available surfaces forming a thin layer with a complex spatial structure called biofi...

The previous chapter presents different views of resilience, starting from Holling’s conceptual definition of “ecological resilience”: the capacity of a system to absorb “disturbance and reorganize while undergoing change so as to still retain essentially the same function, structure, identity, and feedbacks” (Walker et al. 2004). In this chapter,...

In Chap.2, we presented the definition of resilience based on viability theory (Martin 2004), and we argued that this definition is more general than the equilibrium based definition, and fits better the usual meaning of resilience. Several chapters illustrate this approach on individual based models (language dynamics, bacteria, savanna). In each...

Savanna ecosystems cover a substantial percentage of Earth’s land surface area and are economically and socially important (Scholes and Archer 1997; Sankaran et al. 2005; Bond 2008). In addition to harbouring considerable biodiversity, savannas are used extensively by humans, primarily as grazing lands for cattle (Scholes and Archer 1997; Vetter 20...

The study of language dynamics has been addressed from at least three different perspectives: language evolution (or how the structure of language evolves), language cognition (or the way in which the human brain processes linguistic knowledge), and language competition (or the dynamics of language use in multilingual communities). The latter is th...

In a problem of target hitting, the capture basin at cost c is the set of states that can reach the target with a cost lower or equal than c, without breaking the viability constraints. The boundary of a c-capture basin is the c-contour of the problem value function. In this paper, we propose a new algorithm that solves target hitting problems, by...

We propose a new approach to solve target hitting problems, that iteratively approximates capture basins at successive times, using a machine learning algorithm trained on points of a grid with boolean labels. We consider two variants of the approximation (from inside and from outside), and we state the conditions on the machine learning procedure...

In this paper, we present a semi-automatic SOLAP approach specially dedicated to the analysis of spatial model simulation results. We illustrate it on demographic and economic data of rural municipalities resulting from a model developed in the context of the European project PRIMA.

One common characteristic of a complex system is its ability to withstand major disturbances and the capacity to rebuild itself. Understanding how such systems demonstrate resilience by absorbing or recovering from major external perturbations requires both quantitative foundations and a multidisciplinary view of the topic. This book demonstrates h...

We propose to compare discrete and continuous time implementations of a simple birth-death individual-based model (IBM) to analytically de-rived expression of the mean and variance of the population size. Our results show that the discrete time implementation underestimate the variance, especially when increasing the size of the timestep.

Bacteria growth, detachment and surface-associated motility are re-congnized to play an important role in microbial biofilm formation. In this paper we we investigate using an individual-based model how these processes interplay to yield complex biofilm spatial patterns.

In this paper, we present a semi-automatic SOLAP approach specially dedicated to the analysis of spatial model simulation results. We illustrate it on demographic and economic data of rural municipalities resulting from a model developed in the context of the european project PRIMA.