# Andre C. R. MartinsUniversity of São Paulo | USP · School of Arts, Sciences and Humanities

Andre C. R. Martins

PhD in Physics

## About

57

Publications

5,030

Reads

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1,023

Citations

Citations since 2016

Introduction

Andre C. R. Martins currently works at the School of Arts, Sciences and Humanities, University of São Paulo. Andre does research in Opinion Dynamics, Evolutionary Biology, Induction problems, and Theoretical Physics. Their most recent publication is 'Network generation and evolution based on spatial and opinion dynamics components'.

Additional affiliations

August 2010 - August 2011

March 2009 - present

February 2005 - present

**Independent Researcher**

Position

- Universidade de São Paulo

Education

March 1991 - October 1996

**Independent Researcher**

Field of study

- Physics

## Publications

Publications (57)

The question of why we age is a fundamental one. It is about who we are, and it also might have critical practical aspects as we try to find ways to age slower. Or to not age at all. Different reasons point at distinct strategies for the research of anti-ageing drugs. While the main reason why biological systems work as they do is evolution, for qu...

There are many ways we can not know. Even in systems that we created ourselves, as, for example, systems in mathematical logic, Go\"edel and Tarski's theorems impose limits on what we can know. As we try to speak of the real world, things get even harder. We want to compare the results of our mathematical theories to observations, and that means th...

There are several opinion dynamics models where extremism is defined as part of their characteristics. However, the way extremism is implemented in each model does not correspond to equivalent definitions. While some models focus on one aspect of the problem, others focus on different characteristics. This paper shows how each model only captures p...

It has been observed people tend to have opinions that are far more internally consistent than it would be reasonable to expect. Here, we study how that observation might emerge from changing how agents trust the opinions of their peers in a model for opinion dynamics with multiple issues. A previous Bayesian inspired opinion model for continuous o...

Here, I study how to obtain an opinion dynamics model for the case where there are M possible discrete choices and there is a need to model how strong each agent choice is. The new model is obtained as an extension of the Continuous Opinions and Discrete Actions (CODA) model. Technical difficulties with the choice of proper variables for a simple m...

It has been observed people tend to have opinions that are far more internally consistent than it would be reasonable to expect. Here, we study how that observation might emerge from changing how agents trust the opinions of their peers in a model for opinion dynamics with multiple issues. A previous Bayesian inspired opinion model for continuous o...

In this paper, a model for a spatial network evolution based on a Metropolis simulation using an energy function that depends both on the distance between the nodes and the stated preferences is studied. The agents influence their network neighbors using the CODA model, where each agent has a preference between two options based on its probabilisti...

Here, I study how to obtain an opinion dynamics model for the case where there are $M$ possible discrete choices and there is need to model how strong each agent choice is. The new model is obtained as an extension of the Continuous Opinions and Discrete Actions (CODA) model. Technical difficulties with the choice of proper variables for a simple m...

In this paper, a model for a spatial network evolution based on a Metropolis simulation is presented. The model uses an energy function that depends both on the distance between the nodes and the stated preferences. The agents influence their network neighbors opinions using the CODA model. That means each agent has a preference between two options...

Introduction
Most interventions aiming to promote leisure-time physical activity (LTPA) at population level showed small or null effects. Approaching the problem from a systems science perspective may shed light on the reasons for these results. We developed an agent-based model to explore how the interactions between psychological attributes and b...

Despite the increasing body of evidences on the factors influencing leisure-time physical activity, our understanding of the mechanisms and interactions that lead to the formation and evolution of population patterns is still limited. Moreover, most frameworks in this field fail to capture dynamic processes. Our aim was to create a dynamic conceptu...

Evaluating theories in physics used to be easy. Our theories provided very distinct predictions. Experimental accuracy was so small that worrying about epistemological problems was not necessary. That is no longer the case. The underdeterminacy problem between string theory and the standard model for current possible experimental energies is one ex...

When statisticians quarrel about hypothesis testing, the debate usually focus on which method is the correct one. The fundamental question of whether we should test hypothesis at all tends to be forgotten. This lack of debate has its roots on our desire to have ideas we believe and defend. But cognitive experiments have been showing that, when we d...

We believe, in the sense of supporting ideas and considering them correct
while dismissing doubts about them. We take sides about ideas and theories as
if that was the right thing to do. And yet, from a rational point of view, this
type of support and belief is not justifiable at all. The best we can hope when
describing the real world, as far as w...

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...

Abstract Population turnover is necessary for progressive evolution. In the context of a niche with fixed carrying capacity, aging contributes to the rate of population turnover. Theoretically, a population in which death is programmed on a fixed schedule can evolve more rapidly than one in which population turnover is left to a random death rate....

The article discusses the behavioral aspects that affect the entrepreneurs’ decision making under the Knightian uncertainty approach. Since the profit arising from entrepreneurial activity represents the reward of an immeasurable and subjective risk, it has been hypothesized that innovative entrepreneurs have excessive optimism and confidence, whic...

A model for the joint evolution of opinions and how much the agents
trust each other is presented, using the framework of the Continuous
Opinions and Discrete Actions (CODA) model. Instead of a fixed
probability that the other agents will decide in the favor of the best
choice, each agent considers that other agents might be one of two
types: trust...

A model for Opinion Particles, based on Bayesian-inspired models of Opinion
Dynamics such as the CODA model is presented. By extending the discrete time
characteristic of those models to continuous time, a theory for the movement of
opinion particles is obtained, based only on inference ideas. This will allow
inertia to be obtained as a consequence...

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...

Opinion Dynamics tries to model how different opinions spread in a
society. At this point, the existing models lack a common theoretical
basis. In this article, I propose to use a decision-theoretic framework,
based on the updating of subjective probabilities, as that basis. We
will see we get a basic tool for a better understanding of the
interact...

In this Chapter, I will explore the use of modeling in order to understand
how Science works. I will discuss the modeling of scientific communities,
providing a general, non-comprehensive overview of existing models, with a
focus on the use of the tools of Agent-Based Modeling and Opinion Dynamics. A
special attention will be paid to models inspire...

Opinion Dynamics models can be, for most of them, divided between discrete
and continuous. They are used in different circumstances and the relationship
between them is not clear. Here we will explore the relationship between a
model where choices are discrete but opinions are a continuous function (the
Continuous Opinions and Discrete Actions, COD...

Science is a fundamental human activity and we trust its results because it has several error-correcting mechanisms. It is subject to experimental tests that are replicated by independent parts. Given the huge amount of information available and the information asymetry between producers and users of knowledge, scientists have to rely on the report...

Understanding why we age is a long-lived open problem in evolutionary biology. Aging is prejudicial to the individual, and evolutionary forces should prevent it, but many species show signs of senescence as individuals age. Here, I will propose a model for aging based on assumptions that are compatible with evolutionary theory: i) competition is be...

The recent claim that the exit probability (EP) of a slightly modified version of the Sznadj model is a continuous function of the initial magnetization is questioned. This result has been obtained analytically and confirmed by Monte Carlo simulations, simultaneously and independently by two different groups (EPL, 82 (2008) 18006; 18007). It stands...

The recent claim that the exit probability (EP) of a slightly modified version of the Sznadj model is a continuous function of the initial magnetization is questioned. This result has been obtained analytically and confirmed by Monte Carlo simulations, simultaneously and independently by two different groups (EPL, 82 (2008) 18006; 18007). It stands...

The dynamics of a one dimensional Ising spin system is investigated using three families of local update rules, the Galam majority rules, Glauber inflow influences and Sznadj outflow drives. Given an initial density p of up spins the probability to reach a final state with all spins up is calculated exactly for each choice. The various formulas are...

We study the dynamics of the adoption of new products by agents with continuous opinions and discrete actions (CODA). The model is such that the refusal in adopting a new idea or product is increasingly weighted by neighbor agents as evidence against the product. Under these rules, we study the distribution of adoption times and the final proportio...

The Random Parameter model was proposed to explain the structure of the covariance matrix in problems where most, but not all, of the eigenvalues of the covariance matrix can be explained by Random Matrix Theory. In this article, we explore the scaling properties of the model, as observed in the multifractal structure of the simulated time series....

Modeling the conditions for the emergence of extremism is a very important problem, with clear applications for describing the interaction among individuals. Traditional models either are not suited for the task, as in the case of discrete models, or, like Bounded Confidence models, are built with rules that make opinions tend to a common ground be...

In this paper, we study the effects of introducing contrarians in a model of
Opinion Dynamics where the agents have internal continuous opinions, but
exchange information only about a binary choice that is a function of their
continuous opinion, the CODA model. We observe that the hung election scenario
still exists here, but it is weaker and it sh...

Science is a fundamental human activity and we trust its results because it has several error-correcting mechanisms. It is subject to experimental tests that are replicated by independent parts. Given the huge amount of information available, scientists have to rely on the reports of others. This makes it possible for social effects to influence th...

We study opinion dynamics in a population of interacting adaptive agents voting on a set of complex multidimensional issues. We consider agents which can classify issues into for or against. The agents arrive at the opinions about each issue in question using an adaptive algorithm. Adaptation comes from learning and the information for the learning...

Opinion Dynamics lacks a theoretical basis. In this article, I propose to use
a decision-theoretic framework, based on the updating of subjective
probabilities, as that basis. We will see we get a basic tool for a better
understanding of the interaction between the agents in Opinion Dynamics
problems and for creating new models. I will review the f...

Understanding the emergence of extreme opinions and in what kind of environment they might become less extreme is a central theme in our modern globalized society. A model combining continuous opinions and observed discrete actions (CODA) capable of addressing the important issue of measuring how extreme opinions might be has been recently proposed...

Reported results of experiments are usually trustworthy, but some of them might be obtained from errors or deceptive behavior. When an agent only read articles about experimental results and use the articles to update his subjective opinions about different theories, the existence of deception can have severe consequences. An earlier attempt to sol...

In this article, I investigate the use of Bayesian updating rules applied to modeling social agents in the case of continuos opinions models. Given another agent statement about the continuous value of a variable $x$, we will see that interesting dynamics emerge when an agent assigns a likelihood to that value that is a mixture of a Gaussian and a...

The replicator dynamics of players choosing either mixed or pure strategies are usually regarded as equivalent, as long as strategies are played with identical frequencies. In this paper we show that a population of pure strategists can be invaded by mixed strategists in any two-player game with equilibrium coexistence upon the addition of an arbit...

A model where agents show discrete behavior regarding their actions, but have continuous opinions that are updated by interacting with other agents is presented. This new updating rule is applied to both the voter and Sznajd models for interaction between neighbors and its consequences are discussed. The appearance of extremists is naturally observ...

The exact meaning of the noise spectrum of eigenvalues of the correlation matrix is discussed. In order to better understand the possible phenomena behind the observed noise, the spectrum of eigenvalues of the correlation matrix is studied under a model where most of the true eigenvalues are zero and the parameters are non-stationary. The results a...

A parameterization that is a modified version of a previous work is proposed for the returns and correlation matrix of financial time series and its properties are studied. This parameterization allows easy introduction of non-stationarity and it shows several of the characteristics of the true, observed realizations, such as fat tails, volatility...

The exact meaning of the noise spectrum of eigenvalues of the covariance matrix is discussed. In order to better understand the possible phenomena behind the observed noise, the spectrum of eigenvalues of the covariance matrix is studied under a model where most of the true eigenvalues are zero and the parameters are non-stationary. The results are...

In this article, I will show how several observed biases in human probabilistic reasoning can be partially explained as good heuristics for making inferences in an environment where probabilities have uncertainties associated to them. Previous results show that the weight functions and the observed violations of coalescing and stochastic dominance...

I will show that, in the Problem of Old Evidence, unless a rational agent has a property I will call theoretical omniscience (a stronger version of logical omniscience), a problem with non-commutativity of the learning theories follows. Therefore, scientists, when trying to behave as close to rationality as possible, should behave in a way close to...

This article studies what happens when someone tries to decide between two com¬peting ideas simply by reading descriptions of experiments done by others. The agent is modeled as rational person, adopting Bayesian rules and the effect that the possibility that each article might be a deception is analyzed.

Humans make mistakes in our decision-making and probability judgments. While the heuristics used for decision-making have been explained as adaptations that are both efficient and fast, the reasons why people deal with probabilities using the reported biases have not been clear. We will see that some of these biases can be understood as heuristics...

A new evolutionary solution to Prisoner Dilemma situations is proposed in this paper. A specific genetic code may have different phenotypes, meaning different strategies for different individuals carrying that gene. This means that, under the right parameters, it is a good evolutionary solution to create two types of phenotypes with different strat...

## Projects

Project (1)