Stockholms universitet

Fredrik JanssonForskare

Om mig

Researcher in Cultural Evolution
Senior Lecturer in Applied Mathematics

I study human behaviour and its effects on society through mathematics, experiments and simulations. I am currently focusing on issues related to interrelationships between cultural traits, group formation, homophily, segregation and norm change, and am generally interested in issues related to cultural evolution.


Cultural evolution

I am interested in the mechanisms that shape and change human culture, broadly defined as socially learned behaviour. Culture is subject to an evolutionary process: there is variation, it is replicated between individuals and cultural traits have different rates of survival. I have studied the spread of popular traits through turnover rates on toplists, the emergence of Creole languages, and democratic transitions.

Cultural systems

Many phenomena in cultural evolution cannot be explained unless we consider the interdependence between traits. For example, traits vary in compatibility, which should influence their transmission. The belief in Shiva is harder to spread if potential recipients already believe in a monotheistic god. Structural dependencies have the consequence that existing traits influence the acquisition of new traits, and can even provide a mechanistic explanation to the transmission process itself. We use formal modelling to describe cultural systems and agent-based simulations to illustrate the usefulness of this approach for identifying and explaining important properties of cultural evolution and selection biases.

Groups and cooperation

Group membership may be defined through ethnicity, common language, shared preferences or any aggregation of people with some defining characteristics, and leads to widespread phenomena such as ingroup favouritism and polarisation of opinions and attitudes. Previous experiments have shown that these effects can be triggered by even completely arbitrary distinctions between groups. Through game theory and behavioural experiments, I have studied what are possible mechanisms behind group discrimination, and what means there are to increase cooperation between groups.


Groups tend to cluster in society, such that people of similar background end up going to the same schools, workplaces and live in certain neighbourhoods, separated from other groups, with the result of reproducing social inequalities. I have worked on inferring propensities for social ties among immigrants in school based on data on educational choices; simulating residential segregation; surveying people’s attitudes towards ethnically diverse workplaces; and investigated how segregation and polarisation can be mutually reinforcing through social influence.

Norm change and moral values

I am currently conducting experiments on how changes in norms and attitudes can be predicted from the moral foundations of individuals. Previous research on moral foundations has shown that moral judgements are generally based on a limited number of categories. While individuals vary in which categories are important to them, some of these categories are important to almost everyone, and thus seem to drive moral norm change in society.

Democratic transitions

Using data on political institutions, I have examined general patterns for democratic transitions, and was recently involved in a large project on identifying sequences of democratisation processes.


I urval från Stockholms universitets publikationsdatabas

  • A systems approach to cultural evolution

    2019. Andrew Buskell, Magnus Enquist, Fredrik Jansson. Palgrave Communications 5


    A widely accepted view in the cultural evolutionary literature is that culture forms a dynamic system of elements (or 'traits') linked together by a variety of relationships. Despite this, large families of models within the cultural evolutionary literature tend to represent only a small number of traits, or traits without interrelationships. As such, these models may be unable to capture complex dynamics resulting from multiple interrelated traits. Here we put forward a systems approach to cultural evolutionary research-one that explicitly represents numerous cultural traits and their relationships to one another. Basing our discussion on simple graph-based models, we examine the implications of the systems approach in four domains: (i) the cultural evolution of decision rules ('filters') and their influence on the distribution of cultural traits in a population; (ii) the contingency and stochasticity of system trajectories through a structured state space; (iii) how trait interrelationships can modulate rates of cultural change; and (iv) how trait interrelationships can contribute to understandings of inter-group differences in realised traits. We suggest that the preliminary results presented here should inspire greater attention to the role of multiple interrelated traits on cultural evolution, and should motivate attempts to formalise the rich body of analyses and hypotheses within the humanities and social science literatures.

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  • The connection between moral positions and moral arguments drives opinion change

    2019. Pontus Strimling (et al.).


    Liberals and conservatives often take opposing positions on moral issues. But what makes a moral position liberal or conservative? Why does public opinion tend to become more liberal over time? And why does public opinion change especially fast on certain issues, such as gay rights? We offer an explanation based on how different positions connect with different kinds of moral arguments. Based on a formal model of opinion dynamics, we predicted that positions better connected to harm and fairness arguments will be more popular among liberals and will become more popular over time among liberals and conservatives. Finally, the speed of this trend will be faster the better the position connects to harm and fairness arguments. These predictions all held with high accuracy in 44years of polling on moral opinions. The model explains the connection between ideology and moral opinions, and generates precise predictions for future opinion change.

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  • What games support the evolution of an ingroup bias?

    2015. Fredrik Jansson. Journal of Theoretical Biology 373, 100-110


    There is an increasing wealth of models trying to explain the evolution of group discrimination and an ingroup bias. This paper sets out to systematically investigate the most fundamental assumption in these models: in what kind of situations do the interactions take place? What strategic structures – games – support the evolution of an ingroup bias? More specically, the aim here is to find the prerequisites for when a bias also with respect to minimal groups – arbitrarily defined groups void of group-specific qualities – is selected for, and which cannot be ascribed to kin selection.

    Through analyses and simulations of minimal models of two-person games, this paper indicates that only some games are conducive to the evolution of ingroup favouritism. In particular, this class does not contain the prisoners’ dilemma, but it does contain anti-co-ordination and co-ordination games. Contrasting to the prisoners’ dilemma, these are games where it is not a matter of whether to behave altruistically, but rather one of predicting what the other person will be doing, and where I would benefit from you knowing my intentions.

    In anti-co-ordination games, on average, not only will agents discriminate between groups, but also in such a way that their choices maximise the sum of the available payoffs towards the ingroup more often than towards the outgroup. And in co-ordination games, even if agents do manage to co-ordinate with the whole population, they are more likely to co-ordinate on the socially optimal equilibrium within their group. Simulations show that this occurs most often in games where there is a component of risk-taking, and thus trust, involved. A typical such game is the stag hunt or assurance game.

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  • Modeling the Evolution of Creoles

    2015. Fredrik Jansson, Mikael Parkvall, Pontus Strimling. Language Dynamics and Change 5 (1), 1-51


    Various theories have been proposed regarding the origin of creole languages. Describing a process where only the end result is documented involves several methodological difficulties. In this paper we try to address some of the issues by using a novel mathematical model together with detailed empirical data on the origin and structure of Mauritian Creole. Our main focus is on whether Mauritian Creole may have originated only from a mutual desire to communicate, without a target language or prestige bias. Our conclusions are affirmative. With a confirmation bias towards learning from successful communication, the model predicts Mauritian Creole better than any of the input languages, including the lexifier French, thus providing a compelling and specific hypothetical model of how creoles emerge. The results also show that it may be possible for a creole to develop quickly after first contact, and that it was created mostly from material found in the input languages, but without inheriting their morphology.

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  • Social consensus influences ethnic diversity preferences

    2018. Fredrik Jansson, Moa Bursell. Social influence 13 (4), 192-208


    There is widespread segregation between workplaces along ethnic lines. We expand upon previous research on segregation and social influence by testing the effect of the latter on personal diversity preferences, specifically in employees' selection into hypothetical workplaces. In a survey study with 364 European American respondents in three waves, participants complied with social consensus preferences for either more or less workplace diversity. The new preference was sufficiently internalized to be retained largely unaltered a week later. Simulations suggest a self-reinforcing effect, where accurate social consensus information may be sufficient to change preferences. Given that initial choices were polarized, perceived social consensus can vary highly between people in society, and influencing this perception may feed back into greater acceptance of minorities.

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  • Diversity preferences among employees and ethnoracial workplace segregation

    2018. Moa Bursell, Fredrik Jansson. Social Science Research 74, 62-76


    Ethno-racial workplace segregation increases already existing ethno-racial inequality. While previous research has identified discriminatory employers as drivers of workplace segregation, this study addresses the role of the employees. Sociological and social psychological theory suggest that people prefer to surround themselves with people who positively confirm their social identity or who contribute with higher group status. Through web-based surveys, we measure employee attitudes and preferences concerning ethno-racial workplace diversity, to what extent they differ by ethnicity/race, and if they contain intersectional patterns. Thereafter, we use simulation models to analyze the consequences for workplace segregation that these preferences would have, if realized. The main survey results showed that all ethno-racial groups favored their own in-group as colleagues, especially European Americans. As a secondary choice, the respondents preferred the out-group with the highest labor market status. Intersectional patterns were identified, as minority women were preferred as colleagues over minority men. Our simulation model, based on the results of two surveys on stated vs. indirectly revealed preferences, showed that employee preferences were at best not diverse enough to desegregate workplaces. When based on the most common preferences (i.e. excluding a few outliers), the simulations even suggested that these preferences can cause segregation. We relate these findings to Schelling's model of segregation.

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  • Pitfalls in Spatial Modelling of Ethnocentrism

    2013. Fredrik Jansson. JASSS 16 (3)


    Ethnocentrism refers to the tendency to behave differently towards strangers based only on whether they belong to the ingroup or the outgroup. It is a widespread phenomenon that can be triggered by arbitrary cues, but the origins of which are not clearly understood. In a recent simulation model by Hammond and Axelrod, an ingroup bias evolves in the prisoners' dilemma game. However, it will be argued here that the model does little to advance our understanding of ethnocentrism. The model assumes a spatial structure in which agents interact only with their immediate neighbourhood, populated mostly by clones, and the marker becomes an approximate cue of whether the partner is one. It will be shown that agents with an ingroup bias are successful compared to unconditional co-operators since they only exclude non-clones, but are outcompeted by less error-prone kin identifiers. Thus, the results of the simulations can be explained by a simple form of kin selection. These findings illustrate how spatial assumptions can alter a model to the extent that it no longer describes the phenomenon under study.

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  • Democratic revolutions as institutional innovation diffusion

    2013. Fredrik Jansson, Patrik Lindenfors, Mikael Sandberg. Technological forecasting & social change 80 (8), 1546-1556


    Recent ‘democratic revolutions’ in Islamic countries call for a re-consideration of transitions to and from democracy. Transitions to democracy have often been considered the outcome of socio-economic modernization and therefore slow and incremental processes. But as a recent study has made clear, in the last century, transitions to democracy have mainly occurred through rapid leaps rather than slow and incremental steps. Here, we therefore apply an innovation and systems perspective and consider transitions to democracy as processes of institutional, and therefore systemic, innovation adoption. We show that transitions to democracy starting before 1900 lasted for an average of 50 years and a median of 56 years, while transitions originating later took an average of 4.6 years and a median of 1.7 years. However, our results indicate that the survival time of democratic regimes is longer in cases where the transition periods have also been longer, suggesting that patience paid in previous democratizations. We identify a critical ‘consolidation-preparing’ transition period of 12 years. Our results also show that in cases where the transitions have not been made directly from autocracy to democracy, there are no main institutional paths towards democracy. Instead, democracy seems reachable from a variety of directions. This is in line with the analogy of diffusion of innovations at the nation systems level, for which assumptions are that potential adopter systems may vary in susceptibility over time. The adoption of the institutions of democracy therefore corresponds to the adoption of a new political communications standard for a nation, in this case the innovation of involving in principle all adult citizens on an equal basis.

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  • Women's rights in democratic transitions

    2017. Yi-ting Wang (et al.). European Journal of Political Research 56 (4), 735-756


    What determines countries’ successful transition to democracy? This article explores the impact of granting civil rights in authoritarian regimes and especially the gendered aspect of this process. It argues that both men's and women's liberal rights are essential conditions for democratisation to take place: providing both women and men rights reduces an inequality that affects half of the population, thus increasing the costs of repression and enabling the formation of women's organising – historically important to spark protests in initial phases of democratisation. This argument is tested empirically using data that cover 173 countries over the years 1900–2012 and contain more nuanced measures than commonly used. Through novel sequence analysis methods, the results suggest that in order to gain electoral democracy a country first needs to furnish civil liberties to both women and men.

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  • Bentley’s conjecture on popularity toplist turnover under random copying

    2010. Kimmo Eriksson, Fredrik Jansson, Jonas Sjöstrand. The Ramanujan journal 23, 371-396


    Bentley et al studied the turnover rate in popularity toplists in a ’random copying’ model of cultural evolution. Based on simulations of a model with population size N, list length ℓ and invention rate μ, they conjectured a remarkably simple formula for the turnover rate: ℓ√μ. Here we study an overlapping generations version of the random copying model, which can be interpreted as a random walk on the integer partitions of the population size. In this model we show that the conjectured formula, after a slight correction, holds asymptotically.

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  • Procedural priming of a numerical cognitive illusion

    2016. Kimmo Eriksson, Fredrik Jansson. Judgment and decision making 11 (3), 205-212


    A strategy activated in one task may be transferred to subsequent tasks and prevent activation of other strategies that would otherwise come to mind, a mechanism referred to as procedural priming. In a novel application of procedural priming we show that it can make or break cognitive illusions. Our test case is the 1/k illusion, which is based on the same unwarranted mathematical shortcut as the MPG illusion and the time-saving bias. The task is to estimate distances between values of fractions on the form 1/k. Most people given this task intuitively base their estimates on the distances between the denominators (i.e., the reciprocals of the fractions), which may yield very poor estimations of the true distances between the fractions. As expected, the tendency to fall for this illusion is related to cognitive style (Study 1). In order to apply procedural priming we constructed versions of the task in which the illusion is weak, in the sense that most people do not fall for it anymore. We then gave participants both strong illusion and weak illusion versions of the task (Studies 2 and 3). Participants who first did the task in the weak illusion version would often persist with the correct strategy even in the strong illusion version, thus breaking the otherwise strong illusion in the latter task. Conversely, participants who took the strong illusion version first would then often fall for the illusion even in the weak illusion version, thus strengthening the otherwise weak illusion in the latter task.

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  • The cultural evolution of democracy

    2011. Patrik Lindenfors, Fredrik Jansson, Mikael Sandberg. PLoS ONE 6 (11), e28270


    Transitions to democracy are most often considered the outcome of historical modernization processes. Socio-economicchanges, such as increases in per capita GNP, education levels, urbanization and communication, have traditionally been found to be correlates or ‘requisites’ of democratic reform. However, transition times and the number of reform steps havenot been studied comprehensively. Here we show that historically, transitions to democracy have mainly occurred throughrapid leaps rather than slow and incremental transition steps, with a median time from autocracy to democracy of 2.4 years,and overnight in the reverse direction. Our results show that autocracy and democracy have acted as peaks in an evolutionary landscape of possible modes of institutional arrangements. Only scarcely have there been slow incremental transitions. We discuss our results in relation to the application of phylogenetic comparative methods in cultural evolutionand point out that the evolving unit in this system is the institutional arrangement, not the individual country which isinstead better regarded as the ‘host’ for the political system.

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  • Using register data to deduce patterns of social exchange

    2017. Fredrik Jansson. Scandinavian Journal of Public Health 45, 56-61


    This paper presents a novel method for deducting propensities for social exchange between individuals based on the choices they make, and based on factors such as country of origin, sex, school grades and socioeconomic background. The objective here is to disentangle the effect of social ties from the other factors, in order to find patterns of social exchange. This is done through a control-treatment design on analysing available data, where the treatment' is similarity of choices between socially connected individuals, and the control is similarity of choices between non-connected individuals. Structural dependencies are controlled for and effects from different classes are pooled through a mix of methods from network and meta-analysis. The method is demonstrated and tested on Swedish register data on students at upper secondary school. The results show that having similar grades is a predictor of social exchange. Also, previous results from Norwegian data are replicated, showing that students cluster based on country of origin.

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  • Simulating the genesis of Mauritian

    2013. Mikael Parkvall, Fredrik Jansson, Pontus Strimling. Acta Linguistica Hafniensia. International Journal of Structural Linguistics 45 (2), 265-273


    This paper presents a computer simulation of the genesis of Mauritian Creole. The input consists of detailed demographic data and typological information on Mauritian as well as the languages which contributed to its birth. The simulation is deliberately a simplistic one – the idea is to have as few potentially controversial assumptions as possible built into the model, and add additional parameters only to the extent that its output differs from the real-world result. As it turns out, the model generates a language which is highly similar to Mauritian as it is spoken today, and thus, very little “tweaking” seems necessary. Most notably, the model produces the desired result without the postulation of targeted language acquisition, and while one cannot conclude that this was not a part of the creolisation process, our simulation suggests that it is not a necessary assumption.

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