Serge Galam

SciencesPo and French National Centre for Scientific Research (CNRS) · CEVIPOF - Centre for Political Research

Starting from a symmetrical multiple-choice individual, I build a sociophysics model of decision-making. Reducing the choices to two and interactions to pairs recovers the Ising model from physics at zero temperature. The associated equilibrium state results from a spontaneous symmetry breaking, with the whole group sharing a unique choice, which i...

Starting from a symmetrical multiple choice individual I build a sociophysics model of decision making. Reducing the choices to two and interactions to pairs recover the Ising model from physics at zero temperature. The associated equilibrium state is a spontaneous symmetry breaking with the whole group sharing a unique choice selected at random. H...

I am deeply moved and honored by this Special Issue of the journal Physics celebrating my seventieth birthday and forty years of sociophysics [...]

A simple model is built to evaluate quantitatively the individual feeling of the passage of time using a sociophysics approach. Given an objective unit of time like the year, I introduce an individualized mirror-subjective counterpart, which is inversely proportional to the number of objective units of time already experienced by a person. An assoc...

To curb the spread of fake news, I propose an alternative to the current trend of implementing coercive measures. This approach would preserve freedom of speech while neutralizing the social impact of fake news. The proposal relies on creating an environment to naturally sequestrate fake news within quite small networks of people. I illustrate the...

We study the Galam majority rule dynamics with contrarian behavior and an oscillating external propaganda in a population of agents that can adopt one of two possible opinions. In an iteration step, a random agent interacts with three other random agents and takes the majority opinion among the agents with probability p(t) (majority behavior) or th...

In this work, we model an individual social career by a finite-size trajectory along a hexagonal lattice moving only forward. At each bifurcation, the individual makes a free-will choice to follow one or the other branch within an uncertain outcome. Considering that those choices are determined by an individual self built from endogenous characteri...

Political polarization is perceived as a threat to democracies. Using the Galam model of opinion dynamics deployed in a five-dimensional parameter space, I show that polarization is the byproduct of an essential hallmark of a vibrant democratic society, namely the open and informal discussions among agents. Indeed, within a homogeneous social commu...

Processing fragments of data collected on a monitored person to find out whether this person is a would-be terrorist (WT) is very challenging. Moreover, the process has proven to be deceptive, with repeated dramatic failures. To address the issue I suggest a mirror simple model to mimic the process at stake. The model considers a collection of grou...

Political polarization is perceived as a threat to democracies. Using the Galam model of opinion dynamics deployed in a five-dimensional parameter space, I show that polarization is the byproduct of an essential hallmark of a vibrant democratic society, namely open and informal discussions among agents. Indeed, within a homogeneous social community...

A new approach to the understanding of sociological collective behaviour, based on the framework of critical phenomena in physics, is presented. The first step consists of constructing a simple mean-behaviour model and applying it to a strike process in a plant. The model comprises only a limited number of parameters characteristic of the plant con...

I review and extend the set of unifying principles, which allow comparing all models of opinion dynamics within one single frame. Within the Global Unifying Frame (GUF), any specific update rule chosen to study opinion dynamics for discrete individual choices is recast into a probabilistic update formula. The associated dynamics is deployed using a...

Defining interdisciplinary physics today requires first a reformulation of what is physics today, which in turn calls for clarifying what makes a physicist. This assessment results from my forty year journey arguing and fighting to build sociophysics. My view on interdisciplinary physics has thus evolved jumping repeatedly to opposite directions be...

Defining interdisciplinary physics today requires first a reformulation of what is physics today, which in turn calls for clarifying what makes a physicist. This assessment results from my 40-year journey arguing and fighting to build sociophysics. My view on interdisciplinary physics has thus evolved jumping repeatedly to opposite directions befor...

I review and extend the set of unifying principles that allow comparing all models of opinion dynamics within one single frame. Within the Global Unifying Frame (GUF), any specific update rule chosen to study opinion dynamics for discrete individual choices is recast into a probabilistic update formula. The associated dynamics is deployed using a g...

We study the effect of probabilistic distortions to the local majority rules used in the Galam model of opinion dynamics and bottom-up hierarchical voting. A different probability for a flip against the local majority within the discussion group is associated with each ratio of majority/minority. The cases of groups of sizes 3 and 5 are investigate...

We propose a contagion model to describe the evolution of the political voting trends in Brazil after the dictatorship from 1985 to nowadays. We consider a fully-connected population divided in two voting groups, left and right. Each group includes three kinds of agents, sensitives, inflexibles and radicals. While sensitives may shift their left or...

We study the conditions of propagation of an initial emergent practice qualified as extremist within a population adept at a practice perceived as moderate, whether political, societal, or religious. The extremist practice is carried by an initial ultraminority of radicals (R) dispersed among conventionals (C) who are the overwhelming majority in t...

We propose a model to describe the evolution of the political voting trends in Brazil after the dictatorship from 1985 to nowadays. We consider a population divided in two voting groups, left and right. Each group includes three kinds of agents, sensitives, inflexibles and radicals. While sensitives may shift their left or right voting, inflexibles...

We study the conditions of propagation of an initial emergent practice qualified as extremist within a population adept at a practice perceived as moderate, whether political, societal or religious. The extremist practice is carried by an initially ultra-minority of Radicals (R) dispersed among Conventionals (C) who are the overwhelming majority in...

We study the effect of local distortions to the majority rule on the dynamics of opinions using an extension of the Galam model. At each iteration of the local updates of opinion, the new model accounts for different probabilities of a local flip against the local majority as a function of the ratio of majority / minority within the discussing grou...

This paper predicting Trump victory has been submitted before the election and revised after, allowing to add a Foreword and Node Added in Revision to discuss in details the causes of the failure of the prediction. In 2016, Trump was unanimously seen as the loser in the November 8 election. In contrast, using a model of opinion dynamics I have been...

A universal formula is shown to predict the dynamics of public opinion including eventual sudden and unexpected outbreaks of minority opinions within a generic parameter space of five dimensions. The formula is obtained by combining and extending several components of the Galam model of opinion dynamics, otherwise treated separately, into one singl...

In 2016, Trump was unanimously seen as the loser in the November 8 election. In contrast, using a model of opinion dynamics I have been developing for a few decades within the framework of sociophysics, I predicted his victory against all odds. According to the model, the winning paradoxical martingale of 2016, has been Trump capability to activate...

A universal formula is shown to predict the dynamics of public opinion including eventual sudden and unexpected outbreaks of minority opinions within a generic parameter space of five dimensions. The formula is obtained combining and extending several components of Galam model of opinion dynamics, otherwise treated separately, into one single updat...

The dynamics of rumor spreading is investigated using a model with three kinds of agents who are, respectively, the Seeds, the Agnostics, and the Others. While Seeds are the ones who start spreading the rumor being adamantly convinced of its truth, Agnostics reject any kind of rumor and do not believe in conspiracy theories. In between, the Others...

A fair assignment of credit for multi-authored publications is a long-standing issue in scientometrics. In the calculation of the h-index, for instance, all co-authors receive equal credit for a given publication, independent of a given author’s contribution to the work or of the total number of co-authors. Several attempts have been made to distri...

En 2016 les victoires du Brexit et de Trump ont porté un coup sérieux à la capacité prédictive de la plupart des analystes, experts et sondeurs qui ne les avaient pas prévues. Ces votes ont été des événements imprévus qui ne figuraient pas parmi la liste des possibles. Le même type de phénomène soudain et imprévu s’est produit avec le mouvement des...

Asymmetry in contrarian behavior is investigated within the Galam model of opinion dynamics using update groups of size 3 with two competing opinions A and B. Denoting x and y the respective proportions of A and B contrarians, four schemes of implementations are studied. The first scheme activates contrarians after each series of updates with proba...

Asymmetry in contrarian behavior is investigated within the Galam model of opinion dynamics using update groups of size 3 with two competing opinions A and B. Denoting $x$ and $y$ the respective proportions of A and B contrarians, four schemes of implementations are studied. First scheme activates contrarians after each series of updates with proba...

A fair assignment of credit for multi-authored publications is a long-standing issue in scientometrics. In the calculation of the $h$-index, for instance, all co-authors receive equal credit for a given publication, independent of a given author's contribution to the work or of the total number of co-authors. Several attempts have been made to dist...

The dynamics of fake news and rumor spreading is investigated using a model with three kinds of agents who are respectively the Seeds, the Agnostics and the Others. While Seeds are the ones who start spreading the rumor being adamantly convinced of its truth, Agnostics reject any kind of rumor and do not believe in conspiracy theories. In between,...

Sudden and unexpected disruptive phenomena like current French "gilets jaunes" movement, Arab springs, Trump and Brexit victories, put at stake the feasibility of their eventual forecasting. Here we claim that such unpredictable social events are indeed predictable, provided one can build the opinion landscape to identify the underlying dynamics. W...

I revisit the 2017 French Presidential election which opposed the far right National Front candidate Marine Le Pen against the center candidate Emmanuel Macron. While voting intentions for Le Pen stuck below 50% and polls kept predicting her failure, I warned on the emergence of a novel phenomenon I defined as unavowed abstention, which could sudde...

We introduce a model of temporal evolution of political opinions which amounts to a dynamical extension of Galam model in which the number of inflexibles are treated as dynamical variables. We find that the critical value of inflexibles in the original Galam model now turns into a fixed point of the system whose stability controls the phase traject...

Processus de radicalisation, effet seuil, rapport science et religion, place des réseaux sociaux, place des controverses dans la structuration de l'opinion publique, impact des outils institutionnels pour lutter contre la radicalisation, distinction radicalisation politique et religieuse : tels sont les thèmes abordés dans ce double entretien.

This chapter shows that a referendum, whatever the issue at stake, is a mechanism to turn our prejudices and fears into rational choices. To predict the outcome requires identifying the prejudices and fears which are prominent at the moment the referendum takes place. The question of identifying which are the leading active beliefs and prejudices i...

Text-mining analysis can describe evolutions of data, even big data, but between two points many curves can join them depending on the dynamics of the process. If statistics approximation can produce error estimation with tendencies, how modelling of dynamics opinion can produce networks estimations from the data ? This paper studies this research...

The Trump phenomenon is argued to depart from current populist rise in Europe. According to a model of opinion dynamics from sociophysics the machinery of Trump’s amazing success obeys well-defined counter-intuitive rules. Therefore, his success was in principle predictable from the start. The model uses local majority rule arguments and obeys a th...

Ranges of differentiated abstention are shown to reverse an "exact" poll estimate on voting day allowing the minority candidate to win the election. In a two-candidate competition A and B with voting intentions at $I_a$, $I_b=1-I_a$ and respective turnout at $x$ and $y$, there exists a critical value $I_{ac}$ for which $I_{ac}<I_a<\frac{1}{2}$ yiel...

An alternative voting scheme is proposed to fill the democratic gap between a president elected democratically via universal suffrage (deterministic outcome, the actual majority decides), and a president elected by one person randomly selected from the population (probabilistic outcome depending on respective supports). Moving from one voting agent...

The phenomenon of radicalization is investigated within a mixed population composed of core and sensitive subpopulations. The latest includes first to third generation immigrants. Respective ways of life may be partially incompatible. In case of a conflict core agents behave as inflexible about the issue. In contrast, sensitive agents can decide ei...

The substantial turmoil created by both 2000 dot-com crash and 2008 subprime crisis has fueled the belief that the two classical paradigms of economics, which are the invisible hand and the rational agent, are not appropriate to describe market dynamics and should be abandoned at the benefit of alternative new theoretical concepts. At odd with such...

The 2000 dot-com crash and the 2008 subprime crisis have fueled the belief that the two classical paradigms of economics, the invisible hand and the rational agent, are not well appropriate to describe market dynamics and should be abandoned at the benefit of alter- native new theoretical concepts. At odd with such a view, using a simple model of c...

We study the relations between strategies in game theory and the conformity. The latter is a behavior deemed relevant in social psychology and, as shown in several works, it strongly influences many social dynamics. We consider a population of agents that evolves in accordance with a payoff matrix which embodies two main strategies: cooperation and...

We revisit the deduction of the exit probability of the one dimensional Sznajd model through the Kirkwood approximation [F. Slanina et al., Europhys. Lett. 82, 18006 (2008)]. This approximation is peculiar in that in spite of the agreement with simulation results [F. Slanina et al., Europhys. Lett. 82, 18006 (2008), R. Lambiotte and S. Redner, Euro...

The Sznajd model is a spin model, inspired by sociophysics, where 2 aligned spins influence a neighbouring spin to change its orientation. A bit of controversy arised in the literature recently about the properties of its one dimensional case, namely the exit probability, the probability that the system ends up in the "all spins up" state as a func...

The phenomenon of radicalization is investigated within an heterogeneous population composed of a core subpopulation, sharing a way of life locally rooted, and a recently immigrated subpopulation of different origins with ways of life which can be partly in conflict with the local one. While core agents are embedded in the country prominent culture...

According to the classic Galam model of opinion dynamics, each agent participates at each update of an opinion interaction. While the scheme gives everyone the same chance to influence others, in reality, social activity and influence vary considerably from one agent to another. To account for such a feature, we introduce a new individual attribute...

Most models of opinion dynamics are threshold-like. For two competing opinions the dynamics is one-dimensional and the associated opinion flow is shaped by at least two attractors separated by a tipping threshold, not necessarily located at 50 %. Initial supports are thus instrumental to determine the final debate outcome. In contrast, the absence...

We propose a novel approach framed in terms of information theory and entropy to tackle the issue of conspiracy theories propagation. We start with the report of an event (such as 9/11 terroristic attack) represented as a series of individual strings of information denoted respectively by two-state variable E i = ±1, i = 1,. .. , N. Assigning E i v...

We review a model of sociophysics which deals with democratic voting in bottom up hierarchical systems. The connection to the original physical model and technics are outlined underlining both the similarities and the di®erences. Emphasis is put on the numerous novel and counterintuitive results obtained with respect to the associated social and po...

We review a model of sociophysics which deals with democratic voting in bottom up hierarchical systems. The connexion to the original physical model and technics are outlined underlining both the similarities and the differences. Emphasis is put on the numerous novel and counterintuitive results obtained with respect to the associated social and po...

The methodological approach proposed here combines textual statistical analysis and agent-based simulations. The controversy concerning the unusual disappearance of pollinating bees (Apis mellifera) covered in the French press over a period of 13 years was chosen to describe the different stages of this heuristic framework. First, the articles are...

Recent years have witnessed the increasing interest of physicists, mathematicians and computer scientists for socio-economic systems. In our view, the many reasons behind this can be summarized by observing that traditional approaches to disciplines as sociology and economics have dramatically shown their limitations.

The Ising ferromagnetic model on a square lattice is revisited using the Galam unifying frame (GUF), set to investigate two-state opinion-dynamics models. When combined with Metropolis dynamics, an unexpected intermediate "dis/order" regime is found with the coexistence of two attractors associated, respectively, to an ordered and a disordered phas...

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The emergence and spreading of “extreme opinions” are studied in networks with agents sharing mild opinions. The turning extreme shift is driven by social group meetings. The extremization process is apprehended according to the social psychology phenomenon of group polarization and illustrated in the case of terrorism. In particular the focus is o...

Coalition forming is investigated among countries, which are coupled with short range interactions, under the influence of externally-set opposing global alliances. The model extends a recent Natural Model of coalition forming inspired from Statistical Physics, where instabilities are a consequence of decentralized maximization of the individual be...

Behavioral finance has become an increasingly important subfield of finance. However the main parts of behavioral finance, prospect theory included, understand financial markets through individual investment behavior. Behavioral finance thereby ignores any interaction between participants. We introduce a socio-financial model that studies the impac...

This study extends classical models of spreading epidemics to describe the phenomenon of contagious public outrage, which eventually leads to the spread of violence following a disclosure of some unpopular political decisions and/or activity. Accordingly, a mathematical model is proposed to simulate from the start, the internal dynamics by which an...

We present in this paper an approximation that is able to give an analytical expression for the exit probability of the $q$-voter model in one dimension. This expression gives a better fit for the more recent data about simulations in large networks, and as such, departs from the expression $\frac{\rho^q}{\rho^q + (1-\rho)^q}$ found in papers that...

This work investigates the effect of the dissolution of a global alliance in a collective of individual countries where the alliance, together with its antagonist counterpart, has previously generated stable coalitions. The model rests on the global alliance model of coalition forming inspired from Statistical Physics. Instabilities are a consequen...

The dynamics of opinion about the controversy of abnormal death of bees is studied among French speaking journalists using a corpus of 1467 articles published in newspapers during the period 1998–2010. From a systematic textual analysis, each article is tagged to either one of three stances to explain the phenomenon, a uni-factor cause, namely the...

This paper starts from methodological issues dealing with sociological and quantitative interpretation of qualitative and discontinued data when analyzing controversies from a large press corpus. Then authors offer a new approach mixing text mining analysis and agent based modeling. The study case dealing with the controversy of abnormal disappeara...

Controversial public debates driven by incomplete scientific data where nobody can claim absolute certainty, due to the current state of scientific knowledge, are studied. To adopt a cautious balanced attitude based on clear but inconclusive data appears to be a lose-out strategy. In contrast overstating arguments with incorrect claims which cannot...

In this report we show the empirical application of our socio-finance model introduced in Andersen,Vrontos, Dellaportas and Galam (2014).

Le 9 janvier 2014, après un long suspense, et de nombreux rebondissements, le Conseil d’État a validé l’interdiction du spectacle de Dieudonné prévu à Nantes le soir même. Cette décision, inattendue pour beaucoup, a donné lieu à des commentaires et arguments sans fin car de nombreux aspects légitimes et contradictoires étaient et restent en jeu. Le...

Controversial public debates driven by incomplete scientific data where nobody can claim absolute certainty, due to the current state of scientific knowledge, are studied. To adopt a cautious balanced attitude based on clear but inconclusive data appears to be a lose-out strategy. In contrast overstating arguments with incorrect claims which cannot...

Coalition forming is investigated among countries, which are coupled with short range interactions, under the influence of external fields produced by the existence of global alliances. The model rests on the natural model of coalition forming inspired from Statistical Physics, where instabilities are a consequence of decentralized maximization of...

This paper reviews a sociophysics two-state model for opinion forming that has proven heuristic power. The dynamics are driven by repeated small-group discussions; within each group, a local majority rule is applied to update the opinions of agents. Iterating the dynamics leads towards one of two opposite attractors at which every agent shares the...

The drastic effect of local alliances in three-party competition is investigated in democratic hierarchical bottom-up voting. The results are obtained analytically using a model which extends a sociophysics frame introduced in 1986 (Galam in J. Math. Phys. 30:426, 1986) and 1990 (Galam in J. Stat. Phys. 61:943, 1990) to study two-party systems and...

Two models of opinion dynamics are entangled in order to build a more realistic model of inflexibility. The first one is the Galam unifying frame (GUF), which incorporates rational and inflexible agents, and the other one is the Continuous Opinions and Discrete Actions model. While initially in GUF, inflexibility is a fixed given feature of an agen...

The Ising ferromagnetic model on a square lattice is revisited using the Galam Unifying Frame (GUF), set to investigate the dynamics of two-state variable systems within the frame of opinion dynamics. When combined with Metropolis dynamics, an unexpected intermediate "dis/order" phase is found with the coexistence of two attractors associated respe...

The impact of wine experts, wine critics continue influencing the wine market, bloggers of wine lovers suggest personal judgments and give comments on wines they consume. Our work focuses on the impact of wine expert judgments versus the word-to-mouth effect on the dynamics of wine purchasing behavior. We assume the phenomenon is identical to other...

The origins of Sociophysics are discussed from personal testimony. I trace back its history to the late 1970s. The first steps of my 30 years of activities and research to establish and promote the field are reviewed. In particular, the decades long strong opposition from the physics community is emphasized, together with the almost total absence o...

The democratic majority rule voting in democratic bottom-up hierarchical structures is shown to produce under certain conditions dictatorship effects by keeping a minority in power against a huge increase of the opposition. No coercion is necessary, only democratic voting. This result sheds new light in particular on the internal strength of former...

From our current level of investigation of the use of majority rule voting in bottom-up hierarchical structures, we are now in a position to touch on one of the most fascinating features of the “life” of inert matter; the phase transition of a given system from one global organization into another. An example in matter would be going from a liquid...

We are investigating a paradigm of instability in coalition forming among countries, which indeed is intrinsic to any collection of individual groups or other social aggregations. Coalitions among countries are formed by the respective attraction or repulsion caused by the historical bond propensities between the countries, which produced an intric...

The controversy about the cause(s) of abnormal death of bee colonies in France is investigated through an extensive analysis of the french speaking press. A statistical analysis of textual data is first performed on the lexicon used by journalists to describe the facts and to present associated informations during the period 1998-2010. Three states...

The use of bottom-up democratic voting in hierarchical structures was shown to produce some major and unexpected biases which in turn might drive toward the stable establishment of democratic dictatorships. However, this demonstration was performed in the case of two competing parties A and B.

While we have shown up several democratic advantages in the use of bottom-up voting hierarchies, we can now undertake the deconstruction of the “beautiful world of democracy” to account for some very specific and inherent features of human behavior, and in particular, spontaneous wise “cheating.”

Among the numerous topics of social sciences covered by sociophysics, the study of opinion dynamics has become a mainstream of research [1–23]. It is a critical subject since public opinion has become a central issue in modern societies, making the understanding of its underlining mechanisms a major challenge [24–26]. Any progress could have signif...

This overview of my salient models of sociophysics exhibits the potential power of sociophysics with respect to a very large spectrum of social, political, economical, and strategic applications as seen in Fig. 11.1

The analogy, if any, between men and atoms is discussed to single out what can be the contribution from physics to the understanding of human behavior. The basic assumptions of the approach of sociophysics are formulated together with the methodology used to tackle a given problem taken from the social and political worlds [1, 2].

Sociophysics deals with one of the most ancient of human dreams, which is simultaneously its nightmare, i.e., the capability to predict and thus to control human behavior. As is often the case, science fiction creates what science will be able to achieve in the future, preceding in part the reality to come. But while succeeding in embodying some of...

That’s it; we have reached the end point of our journey through the wonderful world of sociophysics, which I hope, you have found beautiful and enlightening. It is time to say goodbye (see Fig. 18.1) but before parting, I would like to reassess the particularities of this book.

Before going to the acknowledgments per se, I would like to pay tribute to the physicists who have been instrumental in my education as a physicist, a very few being adamantly opposed to the very idea of sociophysics and the others being more neutral. I will not disclose their respective names! However, I must confess to their credit that the ones...