What Niche Did Human Cooperativeness Evolve in

The Prisoner’s Dilemma (PD) is widely used to model interaction between unrelated individuals in the study of the evolution of cooperativeness. Many mechanisms have been studied which allow for small founding groups of cooperative individuals to prevail even when all social interaction is characterised as a PD. Here, a brief critical discussion of the role of the PD as the most prominent tool in cooperation research is presented, followed by two new objections to such an exclusive focus on PD-based models. It is highlighted that only 2 of the 726 combinatorially possible strategically unique ordinal 2x2 games have the detrimental characteristics of a PD and that the frequency of PD-type games in a space of games with random payoffs does not exceed about 3.5%. Although this does not compellingly imply that the relevance of PDs is overestimated, in the absence of convergent empirical information about the ancestral human social niche, this finding can be interpreted in favour of a rather neglected answer to the question of how the founding groups of human cooperation themselves came to cooperate: Behavioural and/or psychological mechanisms which evolved for other, possibly more frequent, social interaction situations might have been applied to PD-type dilemmas only later

Social norms of cooperation in small-scale societies

Indirect reciprocity, besides providing a convenient framework to address the evolution of moral systems, offers a simple and plausible explanation for the prevalence of cooperation among unrelated individuals. By helping someone, an individual may increase her/his reputation, which may change the pre-disposition of others to help her/him in the future. This, however, depends on what is reckoned as a good or a bad action, i.e., on the adopted social norm responsible for raising or damaging a reputation. In particular, it remains an open question which social norms are able to foster cooperation in small-scale societies, while enduring the wide plethora of stochastic affects inherent to finite populations. Here we address this problem by studying the stochastic dynamics of cooperation under distinct social norms, showing that the leading norms capable of promoting cooperation depend on the community size. However, only a single norm systematically leads to the highest cooperative standards in small communities. That simple norm dictates that only whoever cooperates with good individuals, and defects against bad ones, deserves a good reputation, a pattern that proves robust to errors, mutations and variations in the intensity of selection.This research was supported by Fundacao para a Ciencia e Tecnologia (FCT) through grants SFRH/BD/94736/2013, PTDC/EEI-SII/5081/2014, PTDC/MAT/STA/3358/2014 and by multi-annual funding of CBMA and INESC-ID (under the projects UID/BIA/04050/2013 and UID/CEC/50021/2013 provided by FCT). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio

The Structure of Mutations and the Evolution of Cooperation

Evolutionary game dynamics in finite populations assumes that all mutations are equally likely, i.e., if there are strategies a single mutation can result in any strategy with probability . However, in biological systems it seems natural that not all mutations can arise from a given state. Certain mutations may be far away, or even be unreachable given the current composition of an evolving population. These distances between strategies (or genotypes) define a topology of mutations that so far has been neglected in evolutionary game theory. In this paper we re-evaluate classic results in the evolution of cooperation departing from the assumption of uniform mutations. We examine two cases: the evolution of reciprocal strategies in a repeated prisoner's dilemma, and the evolution of altruistic punishment in a public goods game. In both cases, alternative but reasonable mutation kernels shift known results in the direction of less cooperation. We therefore show that assuming uniform mutations has a substantial impact on the fate of an evolving population. Our results call for a reassessment of the “model-less” approach to mutations in evolutionary dynamics

Reward and punishment in climate change dilemmas

Mitigating climate change effects involves strategic decisions by individuals that may choose to limit their emissions at a cost. Everyone shares the ensuing benefits and thereby individuals can free ride on the effort of others, which may lead to the tragedy of the commons. For this reason, climate action can be conveniently formulated in terms of Public Goods Dilemmas often assuming that a minimum collective effort is required to ensure any benefit, and that decision-making may be contingent on the risk associated with future losses. Here we investigate the impact of reward and punishment in this type of collective endeavors - coined as collective-risk dilemmas - by means of a dynamic, evolutionary approach. We show that rewards (positive incentives) are essential to initiate cooperation, mostly when the perception of risk is low. On the other hand, we find that sanctions (negative incentives) are instrumental to maintain cooperation. Altogether, our results are gratifying, given the a-priori limitations of effectively implementing sanctions in international agreements. Finally, we show that whenever collective action is most challenging to succeed, the best results are obtained when both rewards and sanctions are synergistically combined into a single policy.This research was supported by Fundacao para a Ciencia e Tecnologia (FCT) through grants PTDC/EEISII/5081/2014 and PTDC/MAT/STA/3358/2014 and by multiannual funding of INESC-ID and CBMA (under the projects UID/CEC/50021/2019 and UID/BIA/04050/2013). F.P.S. acknowledges support from the James S. McDonnell Foundation 21st Century Science Initiative in Understanding Dynamic and Multi-scale Systems Postdoctoral Fellowship Award. All authors declare no competing financial or non-financial interests in relation to the work described

Co-evolutionary dynamics of collective action with signaling for a quorum

Collective signaling for a quorum is found in a wide range of organisms that face collective action problems whose successful solution requires the participation of some quorum of the individuals present. These range from humans, to social insects, to bacteria. The mechanisms involved, the quorum required, and the size of the group may vary. Here we address the general question of the evolution of collective signaling at a high level of abstraction. We investigate the evolutionary dynamics of a population engaging in a signaling N-person game theoretic model. Parameter settings allow for loners and cheaters, and for costly or costless signals. We find a rich dynamics, showing how natural selection, operating on a population of individuals endowed with the simplest strategies, is able to evolve a costly signaling system that allows individuals to respond appropriately to different states of Nature. Signaling robustly promotes cooperative collective action, in particular when coordinated action is most needed and difficult to achieve. Two different signaling systems may emerge depending on Nature's most prevalent states.Funding: This research was supported by FEDER through POFC - COMPETE, FCT-Portugal through grants SFRH/BD/86465/2012, PTDC/MAT/122897/2010, EXPL/EEI-SII/2556/2013, and by multi-annual funding of CMAF-UL, CBMA-UM and INESC-ID (under the projects PEst-OE/BIA/UI4050/2014 and UID/CEC/50021/2013) provided by FCT-Portugal, and by Fundacao Calouste Gulbenkian through the "Stimulus to Research" program for young researchers. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio

Effects of a Suggestion Based Intervention on Human Cooperation in the Stag Hunt Game

Cooperation has been one of the most foundational aspect of human society and is frequently studied via use of “The Stag Hunt” which has been used to tease out factors which may influence cooperation. The present study is the first study to attempt to influence human cooperation by means of positive imagery. Participants included 33 males and 72 females) who listened to either an a 7-minute audio designed to encourage them to trust others or an audio designed to encourage them to trust themselves. Participants played 40 rounds of the Stag Hunt game. The total number of times the participant played stag was recorded. An independent-samples t-test found a significant difference in the scores for the trust others (M= 21.47, SD=3.28) and the trust self (M=19.82, SD=3.92) conditions. This suggests guided imagery tasks may influence cooperation

Communication and cooperation in wild chimpanzees (Pan troglodytes schweinfurthii)

Comparisons between animal and human communication are invaluable for understanding the evolution of language and, as our closest living relatives, chimpanzees can provide particularly important insights into this. Here I examined unimodal (UM) and multimodal (MM) communication in wild chimpanzees, in an integrated manner. I found that although MM signals were produced infrequently, and at lower rates compared to captivity, the vast majority of adult and sub-adult individuals did freely combine vocal, gestural and facial signals to produce MM signals. A total of 48 free MM signal combinations were observed, incorporating a wide range of different signal types from different modalities. Focusing on one specific vocalgestural MM signal, I found that MM combinations and UM gestural signals were more successful in eliciting responses compared to UM vocal signals. To investigate signal function more systematically I focused on one common grooming gesture, the big loud scratch (BLS), and tested several competing functional hypotheses. I found little evidence to support the hypotheses that this signal operates as an attention-getter, or as a referential signal. In contrast, my data suggested that in this community of chimpanzees, the BLS facilitates the negotiation of roles within a grooming bout. Groomers used BLSs to request grooming during grooming bouts and the BLS seemed to show willingness to groom, both to initiate a grooming bout, and potentially during a bout when groomees intend to start grooming their partner. Finally, to explore the theoretical link between the evolution of communication and cooperation I tested whether, on an individual level, there was a positive relationship between communicativeness and cooperativeness in chimpanzees. In contrast to theoretical predictions, I found a significantly negative relationship between these two domains, indicating that more communicative chimpanzees were less cooperative. I explore several potential explanations for this highly unexpected finding

Emergence and self-organization of cooperation

Tese de Doutoramento em Ciências Especialidade em FísicaThis dissertation reports the main work I developed during my Ph.D. program. It contains my contributions to the field of population dynamics and a study of a global problem of cooperation. Evolutionary game theory (EGT) and stochastic population dynamics have proven to be powerful tools to describe frequency-dependent dynamics in evolutionary biology. More recently, EGT has become increasingly popular in the study of social settings and conflict resolution among humans, calling for an extension of the initial framework towards the boundless complexity of human reasoning. Here, I discuss the necessity of introducing different levels of rationality and prospective strategies, proving under which circumstances the equations that govern both rational and rationally-bounded players coincide. Moreover, since decision-making often relies in a continuum of possible options, I propose a novel equation to describe the evolution of populations with a continuum of strategies, analyzing why and when we can discretize the sets of possible strategies. Finally, when finite populations and stochastic effects are considered, the increasing population size or increasing number of individual configurations rapidly renders the analysis of stationary states prohibitive. Here, I also discuss a novel framework that allows us to define a hierarchy of approximations to the stationary distribution of any population dynamics described by a Markov process, overcoming the limitations of existing approaches. These results and methods are general in the sense that they are applicable to the study of different dilemmas and their respective gametheoretical representation. In the last part of this dissertation, I focus on problems related with global coordination for the preservation of a common good, such as climate change governance. Indeed, preventing global warming requires overall cooperation. Contributions will depend on uncertainty of future losses, which plays a key role in decision-making. Here, I discuss an evolutionary game theoretical model – and its stochastic dynamics in finite populations – in which decisions within small groups under high risk and stringent requirements toward success are shown to significantly raise the chances of coordinating to save the planet’s climate. This result calls for a decentralized or polycentric way of coordinating efforts to tame the planet’s climate. I further discuss whether a polycentric structure of multiple small-scale sanctioning institutions provides a viable solution to solve global dilemmas. Such structure is shown to help deterring non-cooperative behavior (when compared with a single global institution), even though it suffers, to a smaller extent, from most of the same problems as the top-down approach: sensitivity to risk perception and to overall uncertainty. Furthermore, I also discuss how world’s wealth inequality may influence the outcome of this type of collective dilemmas, studying how the segregation between rich and poor players harms cooperative behavior, even if rich tend to, at first, compensate for contributions (or lack of them) from the poor. Finally, I discuss in which conditions the establishment of pre-play contracts may help to overcome part of these problems. The results indicate that contracts are more effective if voluntary and more prevalent if small, acting as a costly signaling mechanism for a naturally cooperative group of individuals sharing common goals. This, in turn, if combined with some partnership advantages, creates more incentives to join, allowing both cooperation and the total membership to grow.Esta dissertação é uma coletânea do principal trabalho desenvolvido durante o meu doutoramento. Contém as minhas contribuições para o ramo da dinâmica de populações e o estudo de um problema global de cooperação. A Teoria de Jogos Evolutiva (EGT) e a dinâmica estocástica de populações são identificadas como ferramentas poderosas para descrever a dinâmica evolutiva em Biologia Evolutiva. Mais recentemente, a EGT tem-se tornado mais popular no estudo de sistemas sociais de resolução de con- flitos entre humanos pedindo por uma extensão das ferramentas originais de forma a acomodar a grande complexidade humana. Nesta dissertação, eu discuto a necessidade de introduzir diferentes níveis de racionalidade e estratégias que recorrem a previsões, mostrando em que circunstâncias as equações que governam estratégias racionais e com racionalidade limitada coincidem. Além disso, uma vez que a tomada de decisão muitas vezes incide num contínuo de estratégias possíveis, proponho uma nova equação para descrever a evolução de populações com um contínuo de estratégias. Finalmente, quando as populações são finitas e são considerados os seus efeitos estocásticos, o aumento do tamanho da população ou do número de configurações individuais possíveis rapidamente torna impraticável a análise de estados estacionários. Aqui, eu também discuto uma nova ferramenta que permite definir uma hierarquia de aproximações para a distribuição estacionária de qualquer dinâmica de populações descrita por um processo de Markov, ultrapassando as atuais limitações. Estes resultados e métodos são gerais, no sentido de serem aplicáveis ao estudo de diferentes dilemas e da respetiva representação em termos de teoria de jogos. Na última parte desta dissertação, foco-me em problemas relacionados com a coordenação global para a preservação de um bem comum, como a prevenção das alterações climáticas. De facto, a prevenção do aquecimento global requer cooperação a nível global. Contudo, as contribuições vão depender da incerteza sobre as perdas futuras, o que joga um papel crucial na tomada de decisão dos responsáveis. Aqui discuto um modelo de EGT – e os seus efeitos estocásticos em populações finitas – com o qual mostro que as hipóteses de coordenação para salvar o clima do planeta aumentam significativamente se as decisões forem tomadas no seio de pequenos grupos sobre problemas locais que, por um lado, reflitam menor incerteza e, por outro, onde os requisitos para a tomada de ação possam ser apertados. Este resultado pede uma forma de coordenar os esforços para domar o clima do planeta que seja descentralizada, ou policêntrica. Ainda nesta parte, discuto se uma estrutura policêntrica de múltiplas instituições para sancionar comportamentos de pequena escala providencia uma solução viável para resolver problemas globais. Mostro que essa estrutura ajuda a prevenir comportamentos não cooperativos (quando comparada com uma única instituição global), mesmo que sofra, em menor escala, dos mesmos problemas da alternativa top-down: sensibilidade à perceção do risco de desastre e incerteza, em geral. Além disso, também discuto como é que a desigualdade de capacidade contributiva no mundo pode influenciar o resultado deste tipo de dilemas coletivos, estudando como é que a segregação entre jogadores ricos e pobres prejudica a cooperação, mesmo que os ricos, a princípio, tendam a compensar a falta de contribuições dos pobres. Finalmente, discuto em que condições a criação de contratos pode ajudar a ultrapassar parcialmente estes problemas. Os resultados indicam que os contratos são mais eficientes se voluntários e mais prevalentes se entre poucos membros, funcionando como um mecanismo de sinalização com custo para grupos de indivíduos naturalmente cooperativos. Isto, por sua vez, combinado com vantagens intra-contrato, cria mais incentivos para novas adesões o que torna possíveis o aumento tanto da cooperação como do número de membros