First-authored publications

2023

1. Modelling the role of environmental circumscription in the evolution of inequality

   Cedric Perret, and Thomas E. Currie

   Philosophical Transactions of the Royal Society B: Biological Sciences, Jun 2023

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   Circumscription theory proposes that complex hierarchical societies emerged in areas surrounded by barriers to dispersal, e.g. mountains or seas. This theory has been widely influential but the lack of formal modelling has resulted in theoretical and empirical challenges. This theory shares parallels with reproductive skew models from evolutionary ecology where inequality depends on the capacity of subordinates to escape from despotic leaders. Building on these similarities, we extend reproductive skew models to simulate the concurrent evolution of inequality in many connected groups. Our results show that cost of migration does not directly limit inequality in the long term, but it does control the rate of increase in inequality. Second, we show that levels of inequality can be reduced if there are random errors made by dominants, as these lead to variations that propagate between polities. Third, our model clarifies the concept of circumscription by relating it to geographical features: the size of a region and the connectivity between polities. Overall, our model helps clarify some issues about how migration may affect inequality. We discuss our results in the light of anthropological and archaeological evidence and present the future extensions required to build towards a complete model of circumscription theory. This article is part of the theme issue ‘Evolutionary ecology of inequality’.

2022

1. An investigation of the role of leadership in consensus decision-making

   Cedric Perret, and Simon T. Powers

   Journal of Theoretical Biology, Jun 2022

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   Leadership is a widespread phenomena in social organisms and it is recognised to facilitate coordination between individuals. While the role of leadership in group foraging or swarm movement is well understood, it is not clear if leaders would also benefit more complex forms of coordination. In particular, a number of organisms coordinate by consensus decision-making, where individuals explicitly communicate their opinions until they converge toward a common decision. Taking inspiration from physical sciences, we extend a consensus formation model to integrate leaders, which we define by three traits: persuasiveness, talkativeness, and stubbornness. We use numerical simulations to investigate the effect of the number of leaders and their characteristics on the time a group spends to reach consensus, and the bias in the final decision. We show that having a minority of influential individuals (leaders) and a majority of influenceable individuals (followers) reduces the time to reach consensus, but biases the decision towards the preferences of the leaders. This effect emerges solely from the differences in individuals’ personality traits, with the most determinant trait being the talkativeness of the individuals. Overall, we provide a comprehensive investigation of the effects of leaders and their traits on consensus decision-making.

2021

1. The evolution of moral rules in a model of indirect reciprocity with private assessment

   Cedric Perret, Marcus Krellner, and The Anh Han

   Scientific Reports, Dec 2021

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   Moral rules allow humans to cooperate by indirect reciprocity. Yet, it is not clear which moral rules best implement indirect reciprocity and are favoured by natural selection. Previous studies either considered only public assessment, where individuals are deemed good or bad by all others, or compared a subset of possible strategies. Here we fill this gap by identifying which rules are evolutionary stable strategies (ESS) among all possible moral rules while considering private assessment. We develop an analytical model describing the frequency of long-term cooperation, determining when a strategy can be invaded by another. We show that there are numerous ESSs in absence of errors, which however cease to exist when errors are present. We identify the underlying properties of cooperative ESSs. Overall, this paper provides a first exhaustive evolutionary invasion analysis of moral rules considering private assessment. Moreover, this model is extendable to incorporate higher-order rules and other processes.

2020

1. From disorganized equality to efficient hierarchy: how group size drives the evolution of hierarchy in human societies

   Cedric Perret, Emma Hart, and Simon T. Powers

   Proceedings of the Royal Society B: Biological Sciences, Jun 2020

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   A manifest trend is that larger and more productive human groups shift from distributed to centralized decision-making. Voluntary theories propose that human groups shift to hierarchy to limit scalar stress, i.e. the increase in cost of organization as a group grows. Yet, this hypothesis lacks a mechanistic model to investigate the organizational advantage of hierarchy and its role on its evolution. To fill this gap, we describe social organization by the distribution of individuals’ capacity to influence others. We then integrate this formalization into models of social dynamics and evolutionary dynamics. First, our results demonstrate that hierarchy strongly reduces scalar stress, and that this benefit can emerge solely because leaders and followers differ in their capacity to influence others. Second, the model demonstrates that this benefit can be sufficient to drive the evolution of leader and follower behaviours and ultimately, the transition from small egalitarian to large hierarchical groups.

2. Predation shapes the impact of cancer on population dynamics and the evolution of cancer resistance

   Cedric Perret, Cindy Gidoin, Beata Ujvari, and 2 more authors

   Evolutionary Applications, Jun 2020

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   Cancer is a widespread disease that affects most of the metazoans. However, cancer development is a slow process and, long before causing the death of the individual, may weaken organisms’ capacities and impair their interactions with other species. Yet, the impact of cancer development on biotic interactions, and over the dynamics of the whole ecosystem, is still largely unexplored. As well, the feedback of altered biotic interactions on the evolution of resistance against cancer in the context of community ecology has not been investigated. From this new perspective, we theoretically investigate how cancer can challenge expected interaction outcomes in a predator–prey model system, and how, in return, these altered interaction outcomes could affect evolution of resistance mechanism against cancer. First, we demonstrate a clear difference between prey and predator vulnerability to cancer, with cancer having a limited impact on prey populations. Second, we show that biotic interactions can surprisingly lead to a null or positive effect of cancer on population densities. Finally, our evolutionary analysis sheds light on how biotic interactions can lead to diverse resistance levels in predator populations. While its role in ecosystems is mostly unknown, we demonstrate that cancer in wildlife is an important ecological and evolutionary force to consider.

2019

1. Being a leader or being the leader: The evolution of institutionalised hierarchy

   Cedric Perret, Emma Hart, and Simon T. Powers

   In , Jul 2019

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   Abstract. Human social hierarchy has the unique characteristic of existing in two forms. Firstly, as an informal hierarchy where leaders and followers are implicitly defined by their personal characteristics, and secondly, as an institutional hierarchy where leaders and followers are explicitly appointed by group decision. Although both forms can reduce the time spent in organising collective tasks, institutional hierarchy imposes additional costs. It is therefore natural to question why it emerges at all. The key difference lies in the fact that institutions can create hierarchy with only a single leader, which is unlikely to occur in unregulated informal hierarchy. To investigate if this difference can affect group decision-making and explain the evolution of institutional hierarchy, we first build an opinion-formation model that simulates group decision making. We show that in comparison to informal hierarchy, a single-leader hierarchy reduces (i) the time a group spends to reach consensus, (ii) the variation in consensus time, and (iii) the rate of increase in consensus time as group size increases. We then use this model to simulate the cost of organising a collective action which produces resources, and integrate this into an evolutionary model where individuals can choose between informal or institutional hierarchy. Our results demonstrate that groups evolve preferences towards institutional hierarchy, despite the cost of creating an institution, as it provides a greater organisational advantage which is less affected by group size and inequality.

2018

1. Can justice be fair when it is blind? How social network structures can promote or prevent the evolution of despotism

   Cedric Perret, Simon T. Powers, Jeremy Pitt, and 1 more author

   In , Jul 2018

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Co-authored publications

2023

1. The Cultural Evolution of Sociopolitical Organization: Examining how evolutionary processes acting at different scales have shaped history’s broadest patterns

   Thomas E. Currie, and Cedric Perret

   In The Oxford Handbook of Cultural Evolution, 2023
2. Playing the political game: the coevolution of institutions with group size and political inequality

   Simon T. Powers, Cedric Perret, and Thomas E. Currie

   Philosophical Transactions of the Royal Society B: Biological Sciences, Jun 2023

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   All societies need to form institutional rules to regulate their social interactions. These specify what actions individuals should take in particular situations, and what sanctions will apply if individuals violate these rules. However, forming these institutional rules involves playing a political game—a process of negotiation between individuals that is costly and time-consuming. Intuitively, this cost should be expected to increase as a group becomes larger, which could then select for a transition to hierarchy to keep the cost of playing the political game down as group size increases. However, previous work has lacked a mechanistic yet general model of political games that could formalize this argument and test the conditions under which it holds. We address this by formalizing the political game using a standard consensus formation model. We show that the increasing cost of forming a consensus over institutional rules selects for a transition from egalitarian to hierarchical organization over a wide range of conditions. Playing a political game to form institutional rules in this way captures and unites a previously disparate set of voluntary theories for hierarchy formation, and can explain why the increasing group size in the Neolithic would lead to strong political inequality. This article is part of the theme issue ‘Evolutionary ecology of inequality’.

3. Social diversity reduces the complexity and cost of fostering fairness

   Theodor Cimpeanu, Alessandro Di Stefano, Cedric Perret, and 1 more author

   Chaos, Solitons & Fractals, Feb 2023

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   Institutions and investors are constantly faced with the challenge of appropriately distributing endowments. No budget is limitless and optimising overall spending without sacrificing positive outcomes has been approached and resolved using several heuristics. To date, prior works have failed to consider how to encourage fairness in a population where social diversity is ubiquitous, and in which investors can only partially observe the population. Herein, by incorporating social diversity in the Ultimatum game through heterogeneous graphs, we investigate the effects of several interference mechanisms which assume incomplete information and flexible standards of fairness. We quantify the role of diversity and show how it reduces the need for information gathering, allowing us to relax a strict, costly interference process. Furthermore, we find that the influence of certain individuals, expressed by different network centrality measures, can be exploited to further reduce spending if minimal fairness requirements are lowered. Our results indicate that diversity changes and opens up novel mechanisms available to institutions wishing to promote fairness. Overall, our analysis provides novel insights to guide institutional policies in socially diverse complex systems.

2021

1. The cultural evolution and ecology of institutions

   Thomas E. Currie, Marco Campenni, Adam Flitton, and 4 more authors

   Philosophical Transactions of the Royal Society B: Biological Sciences, Jul 2021

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   Human societies are structured by what we refer to as ‘institutions’, which are socially created and culturally inherited proscriptions on behaviour that define roles and set expectations about social interactions. The study of institutions in several social science fields has provided many important insights that have not been fully appreciated in the evolutionary human sciences. However, such research has often lacked a shared understanding of general processes of change that shape institutional diversity across space and time. We argue that evolutionary theory can provide a useful framework for synthesizing information from different disciplines to address issues such as how and why institutions change over time, how institutional rules co-evolve with other culturally inherited traits, and the role that ecological factors might play in shaping institutional diversity. We argue that we can gain important insights by applying cultural evolutionary thinking to the study of institutions, but that we also need to expand and adapt our approaches to better handle the ways that institutions work, and how they might change over time. In this paper, we illustrate our approach by describing macro-scale empirical comparative analyses that demonstrate how evolutionary theory can be used to generate and test hypotheses about the processes that have shaped some of the major patterns we see in institutional diversity over time and across the world today. We then go on to discuss how we might usefully develop micro-scale models of institutional change by adapting concepts from game theory and agent-based modelling. We end by considering current challenges and areas for future research, and the potential implications for other areas of study and real-world applications. This article is part of the theme issue ‘Foundations of cultural evolution’.

2. When to (or not to) trust intelligent machines: Insights from an evolutionary game theory analysis of trust in repeated games

   The Anh Han, Cedric Perret, and Simon T. Powers

   Cognitive Systems Research, Aug 2021

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   The actions of intelligent agents, such as chatbots, recommender systems, and virtual assistants are typically not fully transparent to the user. Consequently, users take the risk that such agents act in ways opposed to the users’ preferences or goals. It is often argued that people use trust as a cognitive shortcut to reduce the complexity of such interactions. Here we formalise this by using the methods of evolutionary game theory to study the viability of trust-based strategies in repeated games. These are reciprocal strategies that cooperate as long as the other player is observed to be cooperating. Unlike classic reciprocal strategies, once mutual cooperation has been observed for a threshold number of rounds they stop checking their co-player’s behaviour every round, and instead only check it with some probability. By doing so, they reduce the opportunity cost of verifying whether the action of their co-player was actually cooperative. We demonstrate that these trust-based strategies can outcompete strategies that are always conditional, such as Tit-for-Tat, when the opportunity cost is non-negligible. We argue that this cost is likely to be greater when the interaction is between people and intelligent agents, because of the reduced transparency of the agent. Consequently, we expect people to use trust-based strategies more frequently in interactions with intelligent agents. Our results provide new, important insights into the design of mechanisms for facilitating interactions between humans and intelligent agents, where trust is an essential factor.

3. Cost-efficient interventions for promoting fairness in the ultimatum game

   Theodor Cimpeanu, Cedric Perret, and The Anh Han

   Knowledge-Based Systems, Dec 2021

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   Institutions and investors face the constant challenge of making accurate decisions and predictions regarding how best they should distribute their endowments. The problem of achieving an optimal outcome at a minimal cost has been extensively studied and resolved using several heuristics. However, these works usually failed to address how an external party can target different types of fair behaviour or do not take into account how limited information can shape this complex interplay. Here, we consider the Ultimatum game in a spatial setting and propose a hierarchy of interference mechanisms based on the amount of information available to an external decision-maker and desired standards of fairness. Our analysis reveals that monitoring the population at a macroscopic level requires more strict information gathering in order to obtain an optimal outcome and that local observations can mediate this requirement. Moreover, we identify the conditions which must be met for an individual to be eligible for investment in order to avoid unnecessary spending. We further explore the effects of varying mutation or behavioural exploration rates on the choice of investment strategy and total accumulated costs to the investor. Overall, our analysis provides new insights about efficient heuristics for cost-efficient promotion of fairness in societies. Finally, we discuss the differences between our findings and previous work done on cooperation dilemmas and present our suggestions for promoting fairness as an external decision-maker.

2018

1. Trusting intelligent machines: Deepening trust within socio-technical systems

   Peter Andras, Lukas Esterle, Michael Guckert, and 7 more authors

   IEEE Technology and Society Magazine, Dec 2018