Rainer Hegselmann - Academia.edu (original) (raw)

Papers by Rainer Hegselmann

Journal of Artificial Societies and Social Simulation, Dec 31, 2022

In the bounded confidence model (BC-model) (Hegselmann & Krause 2002), period by period, all agen... more In the bounded confidence model (BC-model) (Hegselmann & Krause 2002), period by period, all agents average over all opinions that are no further away from their actual opinion than a given distance ϵ, i.e., their 'bound of confidence'. With the benefit of hindsight, it is clear that we completely overlooked a crucial feature of our model back in 2002. That is for increasing values of ϵ, our analysis suggested smooth transitions in model behaviour. However, the transitions are in fact wild, chaotic and non-monotonic-as described by Jan Lorenz (2006). The most dramatic example of these effects is a consensus that breaks down for larger values of ϵ. The core of this article is a fundamentally new approach to the analysis of the BC-model. This new approach makes the non-monotonicities unmissable. To understand this approach, we start with the question: how many different BC processes can we initiate with any given start distribution? The answer to this question is almost certainly for all possible start distributions and certainly in all cases analysed here, it is always a finite number of ϵ-values that make a difference for the processes we start. Moreover, there is an algorithm that finds, for any start distribution, the complete list of ϵ-values that make a difference. Using this list, we can then go directly through all the possible BC-processes given the start distribution. We can therefore check them for non-monotonicity of any kind, and will be able to find them all. This good news comes however with bad news. That is the algorithm that inevitably and without exception finds all the ϵ-values that matter requires exact arithmetics, without any rounding and without even the slightest rounding error. As a consequence, we have to abandon the usual floating-point arithmetic used in today's computers and programming languages. What we need to use instead is absolutely exact fractional arithmetic with integers of arbitrary length. This numerical approach is feasible on all modern computers. The new analytical approach and results are likely to have implications for many applications of the BC-model.

ObjectivesWe measured attitudes towards “immunity passports” in the context of COVID-19 of a larg... more ObjectivesWe measured attitudes towards “immunity passports” in the context of COVID-19 of a large sample of scientists. Consensus of scientists’ opinions on a different aspect of immunity passports was assessed.MethodsWe designed and implemented a survey to capture what scientists from around the world and different scientific background think about immunity certification. The survey was sent to the corresponding authors of scholarly articles published in the last five years in the top 20-ranked journals in each of the 27 subject areas between May and June 2020. Responses from 12,738 scientists were captured, and their distribution was tabulated by participants in health science and other fields. Consensus of responses was calculated using a variant of Shannon Entropy, made suitable for the ordinal response variables.ResultsHalf of the scientists surveyed, regardless of academic background agree that a potential immunity passport program will be good for public health (50.2%) and t...

Neue Realitäten. Herausforderung der Philosophie, 1995

Wirtschaftsethische Perspektiven II., 2021

Advances in the Sociology of Trust and Cooperation, 2020

In the bounded confidence model agents update their opinions by averaging over all opinions that ... more In the bounded confidence model agents update their opinions by averaging over all opinions that are not too far away from their own opinion. The article gives a precise definition of the basic model, offers several interpretations of the model, and introduces two simple extensions that allow to analyze polarization and radicalization. The basic model and its two extensions are seemingly simple. But the simplicity is deceptive. Lots of counterintuitive effects come as a surprise. Additionally, the article demonstrates that in terms of explanatory understanding of mechanisms, it makes a lot of sense to work with deterministic idealizations of random start distributions. 9.1 Introduction The so-called bounded confidence model (BC model) spells out a simple idea: In their ongoing exchange of opinions, individuals (or agents) take seriously those others whose opinions are not too far removed from their own. The core of this article are two extensions of the basic BC model. The first extension (Section 9.2) introduces a bias of the type: "Leftists listen more to the left, rightists listen more to the right." We show how, given the bias, strongly polarized camps of radicalized agents can evolve endogenously. In the second extension (Section 9.3) a group of radicals enters the field. Different from normal agents, the radicals simply stick to their radical opinionno other view is taken seriously. We analyze how normal agents that take seriously opinions that are not to far removed from their own opinion, may or may not become radical. This article also has a methodological objective. I want to demonstrate that the following is a fruitful approach: First, we initialise all our opinion dynamics with the same, constant start distribution. It is a very special, namely representative start distribution: it idealizes deterministically high numbers of random start distributions. Second, in tiny steps, a selected parameter is varied. Then, by direct comparisons of single runs of the system, we try to get an understanding of the dynamics. In contrast to laboratory experiments, such an approach is easy to implement with the help

Begegnungen mit Hans Albert, 2018

Geboren 1950, habe ich in den 60er Jahren mit dem Lesen, Denken und ersten Schreibversuchen begon... more Geboren 1950, habe ich in den 60er Jahren mit dem Lesen, Denken und ersten Schreibversuchen begonnen. In einer Arbeiterfamilie mit einem katholischen Vater und einer protestantischen Mutter aufwachsend, wurde ich zunachst sehr katholisch gepragt. Genauer gesagt, im Alter von zwolf, dreizehn oder auch vierzehn Jahren war ich ein katholischer Fundamentalist.

Artificial Intelligence, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Deutsches Jahrbuch Philosophie, 2011

Kyklos, 2020

SUMMARYA pandemic is not only a biological event and a public health disaster, but it also genera... more SUMMARYA pandemic is not only a biological event and a public health disaster, but it also generates impacts that are worth understanding from economic, societal, historical, and cultural perspectives. In this contribution, we argue that as the disease spreads, we are able to harness a valuable key resource: people who have immunity to coronavirus. This vital resource must be effectively employed, it must be certified, it must be searched for, it must be found, and it may even be actively produced. We discuss why this needs to be done and how this can be achieved. Our arguments not only apply to the current pandemic but also to any future rapidly spreading, infectious disease epidemics. In addition, we argue for high awareness of a major secondary, nonbiological crisis arising from the side effects of societal and economic pandemic reactions to actual or imagined health risks. There is a risk that the impacts of the secondary crisis could outweigh that of the biological event.

The American Mathematical Monthly, 2019

During the last several years opinion dynamics, in particular the question of a consensus, have b... more During the last several years opinion dynamics, in particular the question of a consensus, have been studied by many researchers across various disciplines, ranging from physics, computer science, and electrical engineering to biology, economics, and sociology. Considering the mathematical analysis, the framework of multiagent systems has proven to be very useful. This article explores convergence behavior of d-dimensional multiagent systems x(t + 1) = A(t)x(t) with particular emphasis on opinion dynamics under bounded confidence. Conditions are given that guarantee geometrically fast convergence to consensus, sharpening in particular a well-known theorem on Markov chains. A crucial condition to get consensus is what we call the principle of the third agent. In case overall consensus is not reachable, the process of fragmentation is analyzed and partial consensus among agents is proven given certain assumptions. Using these assumptions, the principle of the third agent holds for subgroups of agents.

Journal of Artificial Societies and Social Simulation, 2017

The Journal of Mathematical Sociology (JMS) started in 1971. The second issue contained its most ... more The Journal of Mathematical Sociology (JMS) started in 1971. The second issue contained its most cited article: Thomas C. Schelling, "Dynamic Models of Segregation". In that article, Schelling presented a family of models, one of which became a canonical model. To date it is called the Schelling model-an eponym that affixes the inventor's name to the invention, one of the highest forms of scientific recognition. In the very first issue of JMS, James Minoru Sakoda published an article entitled "The Checkerboard Model of Social Interaction". Sakoda's article more or less went unrecognized. Yet, a careful comparison demonstrates that in a certain sense the Schelling model is just an instance of Sakoda's model. A precursor of that model was already part of Sakoda's 1949 dissertation submitted to the University of California at Berkeley. A substantial amount of evidence indicates that in the 1970s Sakoda was well known and recognized as a computational social scientist, whereas Schelling was an unknown in the field. A generation later, the pattern of recognition almost completely reversed: Sakoda had become the unknown, while Schelling was the well-known inventor of the pioneering Schelling model. This article explains this puzzling pattern of recognition. Technical and social factors play a decisive role. Some contrafactual historical reflection suggests that the final result was not inevitable.

Journal of Artificial Societies and Social Simulation, 2012

Beiträge zur Geschichte und Wirkung des Wiener Kreises

RAINER HEGsELMANN Die Korrespondenz zwischen Otto Neurath und Rudolf Carnap aus den Jahren 1934 b... more RAINER HEGsELMANN Die Korrespondenz zwischen Otto Neurath und Rudolf Carnap aus den Jahren 1934 bis 1945— Ein vorläufiger Bericht' Der hier behandelte Teil des Briefwechsels zwischen Neurath und Carnap setzt ein im März 1934, 2 also zu einer Zeit, wo Neurath ...

Festschrift für Franz von Kutschera

The article describes a radically simplifying model of opinion formation processes. The model abs... more The article describes a radically simplifying model of opinion formation processes. The model abstracts away almost everything. A very common reaction to such an approach is the objection that important factors are not included. The article anticipates ten objections of this type and tries to show how to cope with them without giving up the radically simplifying approach. The strategies that we use can be summarized to a certain heuristics. Following the principles of this heuristics will often allow at least a partial qualitative understanding of real world phenomena. In many areas we probably cannot hope for more. * Die hier vorgestellten Resultate beruhen auf gemeinsamer Forschung und entsprechend vielen Diskussionen mit Ulrich Krause (Universität Bremen). An vielen Stellen wird auf die Arbeit Hegselmann und Krause 2002 sowie Hegselmann und Krause 2004 zurückgegriffen. Insgesamt ist der Artikel eine überarbeitete deutsche Fassung von Hegselmann 2004.