Transitions between homophilic and heterophilic modes of cooperation

Cooperation is ubiquitous in biological and social systems. Previous studies revealed that a preference toward similar appearance promotes cooperation, a phenomenon called tag-mediated cooperation or communitarian cooperation. This effect is enhanced when a spatial structure is incorporated, because space allows agents sharing an identical tag to regroup to form locally cooperative clusters. In spatially distributed settings, one can also consider migration of organisms, which has a potential to further promote evolution of cooperation by facilitating spatial clustering. However, it has not yet been considered in spatial tag-mediated cooperation models. Here we show, using computer simulations of a spatial model of evolutionary games with organismal migration, that tag-based segregation and homophilic cooperation arise for a wide range of parameters. In the meantime, our results also show another evolutionarily stable outcome, where a high level of heterophilic cooperation is maintained in spatially well-mixed patterns. We found that these two different forms of tag-mediated cooperation appear alternately as the parameter for temptation to defect is increased.Comment: 16 pages, 7 figure

Evolutionary dynamics of homophily and heterophily

Most social interactions do not take place at random. In many situations, individuals choose their interaction partners on the basis of phenotypic cues. When this happens, individuals are often homophilic, that is, they tend to interact with individuals that are similar to them. Here we investigate the joint evolution of phenotypic cues and cue-dependent interaction strategies. By a combination of individual-based simulations and analytical arguments, we show that homophily evolves less easily than earlier studies suggest. The evolutionary interplay of cues and cue-based behaviour is intricate and has many interesting facets. For example, an interaction strategy like heterophily may stably persist in the population even if it is selected against in association with any particular cue. Homophily persisted for extensive periods of time just in those simulations where homophilic interactions provide a lower (rather than a higher) payoff than heterophilic interactions. Our results indicate that even the simplest cue-based social interactions can have rich dynamics and a surprising diversity of evolutionary outcomes

Intragenerational Cultural Evolution and Ethnocentrism

Ethnocentrism denotes a positive orientation towards those sharing the same ethnicity and a negative one towards others. Previous models demonstrated how ethnocentrism might evolve inter-generationally (vertically) when ethnicity and behavior is inherited. We model short-term intra-generational (horizontal) cultural adaptation where agents have a fixed ethnicity but have the ability to form and join fluid cultural groups and to change how they define their in-group based on both ethnic and cultural markers. We find that fluid cultural markers become the dominant way that agents identify their ingroup supporting positive interaction between ethnicities. However, in some circumstances, discrimination evolves in terms of a combination of cultural and ethnic markers producing bouts of ethnocentrism. This suggests the hypothesis that in human societies, even in the absence of direct selection on ethnic marker based discrimination, selection on the use of fluid cultural markers can lead to marked changes in ethnocentrism within a generation

Young children discriminate genuine from fake smiles and expect people displaying genuine smiles to be more prosocial

We investigated when young children become sensitive to one evolutionary important signal of honest affiliative and cooperative intent: a genuine (Duchenne) smile. Altogether, we tested 168 children between 2 and 5 years of age in a series of studies aimed at mapping the development of children's ability to discriminate genuine from fake smiles, their preference for genuine smiles, and their understanding of how genuine smiles are linked with prosocial behavior. Studies 1–4 showed that children's ability to discriminate, and answer questions about, the different types of smiles gradually improves between the ages of 2 and 4 years: from implicitly discriminating the smiles in their gaze behavior (at age 3), to being able to identify genuine smiles explicitly in a verbal task (at age 4). Study 5 showed that 4- to 5-year-old children expect people displaying genuine smiles to be more prosocial than those displaying fake smiles. These results demonstrate that the origins of this evolutionarily important form of partner choice appear early in development

The Fitness Costs and Regulatory Strategies of Cooperative Siderophore Production in Pseudomonas

Cooperative behaviors in bacteria are increasingly appreciated for their relevance to microbial ecology and utility as model systems for social evolution. One example is the secretion of siderophores, a structurally diverse group of compounds that chelate extracellular iron. Siderophore production is considered cooperative because the benefits can be shared with neighboring cells, provided they have a suitable uptake system. As a cooperative behavior, evolutionary theory predicts siderophore production should be vulnerable to exploitation by free-loaders who reap the benefits without equal investment. Indeed, natural isolates often express receptors for siderophores they do not produce, indicating that social conflict is ecologically relevant. However, many questions remain unanswered regarding the influence of social conflict on the evolution of siderophore-producing populations. Specifically, the environmental conditions conducive to free-loading are not fully understood, obscuring efforts to distinguish whether siderophore-negative isolates evolved as social cheaters or are a result of non-social adaptations. It is also unknown how bacterial phenotypes are regulated to optimize fitness when competing with other siderophore producers. The results presented here provide insight into these two questions. We first investigated the relationship between nutrient limitation and the fitness cost of pyoverdine (PVD) production, the primary siderophore of the medically relevant model organism Pseudomonas aeruginosa. Using metabolic modeling, we showed PVD production, although energetically costly, does not influence growth rate unless a building block of PVD (carbon or nitrogen) is limiting. When growth is limited by any other nutrient such that carbon and nitrogen are in relative excess, PVD production does not compete with the generation of cellular biomass and therefore does not reduce the growth rate. We confirmed these results experimentally with a continuous-culture approach. We showed that isogenic PVD-negative mutants act as free-loaders in co-culture with a PVD-producing wild-type when limited by carbon, but not when limited by phosphorus. Second, we focused on the competitive strategies of soil bacterium Pseudomonas protegens Pf-5, a biocontrol strain remarkable for its ability to use dozens of siderophores it does not make. We found that while Pf-5 is able to regulate its receptors dynamically to reflect siderophore availability, it continues to secrete its own primary siderophore PVDPf-5, declining the opportunity to free-load. We demonstrated that this strategy is beneficial in co-culture with a competing PVD producer, P. aeruginosa PAO1. Although Pf-5 can use PAO1’s siderophore, Pf-5 must continue to produce its own to maintain a competitive advantage. We attribute this to an antagonistic effect of PVDPf-5 on the growth of PAO1, presumably through limiting access to iron. Our results demonstrate the benefits of excluding competitors exceed the incentives associated with a free-loader lifestyle for Pf-5. Our findings are important not only for a fundamental understanding of microbial populations, but also for contexts highly relevant to humans, including human infections and agricultural applications. The principle of nutrient-dependent fitness costs has implications for the not only the stability of cooperation in the PVD model system, but also cooperation in general. Our work with Pf-5 emphasizes that complex strategies beyond free-loading are also relevant to siderophore social dynamics. Collectively, our findings contribute to a predictive understanding of how social dynamics influence the evolution and stability of siderophore production

Robust Systems of Cooperation

This dissertation examines the robustness of systems of cooperation—the ability to maintain levels of cooperation in the presence of a potentially disruptive force. I examine rankings as a potentially disruptive force that is commonplace in organizations. A ranking is the ordering of individuals according to their performance on a specific dimension. Systems of cooperation often operate in contexts that feature rankings (e.g., the ride-sharing company Uber uses a “rank and yank” performance evaluation system, yet still expects cooperation on complex cooperative coding tasks) and some explicitly use rankings to motivate cooperative contributions toward a collective goal (e.g., the character improvement App “Peeple” consists of members’ public evaluations of each other’s character and uses a public “positivity rating” to motivate members to maintain a more collegial environment). Yet, a growing body of research is highlighting potential downsides to rankings that could undermine the maintenance of systems of cooperation. This research suggests that rankings may unexpectedly introduce new dynamics into a system of cooperation that drive actors toward uncooperative behaviors and undermine the system as a whole. This dissertation aims to address this tension by exploring how systems of cooperation interact with rankings. Specifically, it explores how rankings can both enrich and perturb a system of cooperation and how systems can achieve robust cooperation in the presence of rankings. Chapter 1 introduces the dual role of rankings for systems of cooperation, reflects on the importance of identifying characteristics that make these systems robust, and discusses how the changing nature of work creates a new urgency for understanding how rankings affect cooperation. This introductory chapter is followed by two empirical chapters that examine distinct pieces of the puzzle for how rankings affect the maintenance of cooperation over time. Chapter 2 examines how the introduction of a performance ranking affects established systems of cooperation. Using a between-groups, no-deception experimental design that includes 74 groups, 594 participants, and over 11,000 cooperation decisions, it examines 1) whether the self-sustaining properties of systems of cooperation are naturally able to overcome the potentially disruptive effects of rankings, and 2) in the case of disruption how managers may be able to restore cooperation in the presence of rankings—making these systems of cooperation more robust. Chapter 3 examines an online community that explicitly uses a ranking to promote cooperation. Using over 1.2 million observations of members’ weekly behaviors, this chapter examines how potential losses and gains in rank inspire individuals to perform both cooperative and uncooperative behaviors and explores how the system-level implications of these behaviors may affect the robustness of systems of cooperation. Chapter 4 concludes the dissertation by synthesizing findings from the empirical chapters, discussing their joint implications for building robust systems of cooperation, and detailing areas of future research.PHDBusiness AdministrationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145900/1/caceves_1.pd

Common minds, uncommon thoughts: a philosophical anthropological investigation of uniquely human creative behavior, with an emphasis on artistic ability, religious reflection, and scientific study

The aim of this dissertation is to create a naturalistic philosophical picture of creative capacities that are specific to our species, focusing on artistic ability, religious reflection, and scientific study. By integrating data from diverse domains (evolutionary and developmental psychology, cognitive anthropology and archeology, neuroscience) within a philosophical anthropological framework, I have presented a cognitive and evolutionary approach to the question of why humans, but not other animals engage in such activities. Through an application of cognitive and evolutionary perspectives to the study of these behaviors, I have sought to provide a more solid footing for philosophical anthropological discussions of uniquely human behavior. In particular, I have argued that art, religion and science, which are usually seen as achievements that are quite remote from ordinary modes of reasoning, are subserved by evolved cognitive processes that serve functions in everyday cognitive tasks, that arise early and spontaneously in cognitive development, that are shared cross-culturally, and that have evolved in response to selective pressures in our ancestral past. These mundane cognitive processes provide a measuring rod with which we can assess a diversity of cultural phenomena; they form a unified explanatory framework to approach human culture. I have argued that we can explain uncommon thoughts (exceptional human achievements, such as art, religion and science) in terms of interactions between common minds (ordinary human minds that share their knowledge through cultural transmission). This dissertation is subdivided into four parts. Part I outlines the problem of human uniqueness, examining theories on how humans conceptualize the world, and what their mental tool box looks like. Part II discusses the evolutionary and cognitive origins of human artistic behavior. Part III focuses on the cognitive science of religion, especially on how it can be applied to the reasoning of theologians and philosophers of religion. Part IV considers the cognitive basis of scientific practice

Modelling religious signalling

The origins of human social cooperation confound simple evolutionary explanation. But from Darwin and Durkheim onwards, theorists (anthropologists and sociologists especially) have posited a potential link with another curious and distinctively human social trait that cries out for explanation: religion. This dissertation explores one contemporary theory of the co-evolution of religion and human social cooperation: the signalling theory of religion, or religious signalling theory (RST). According to the signalling theory, participation in social religion (and its associated rituals and sanctions) acts as an honest signal of one's commitment to a religiously demarcated community and its way of doing things. This signal would allow prosocial individuals to positively assort with one another for mutual advantage, to the exclusion of more exploitative individuals. In effect, the theory offers a way that religion and cooperation might explain one another, but which that stays within an individualist adaptive paradigm. My approach is not to assess the empirical adequacy of the religious signalling explanation or contrast it with other explanations, but rather to deal with the theory in its own terms - isolating and fleshing out its core commitments, explanatory potential, and limitations. The key to this is acknowledging the internal complexities of signalling theory, with respect to the available models of honest signalling and the extent of their fit (or otherwise) with religion as a target system. The method is to take seriously the findings of formal modelling in animal signalling and other disciplines, and to apply these (and methods from the philosophy of biology more generally) to progressively build up a comprehensive picture of the theory, its inherent strengths and weaknesses. The first two chapters outline the dual explanatory problems that cooperation and religion present for evolutionary human science, and surveys contemporary approaches toward explaining them. Chapter three articulates an evolutionary conception of the signalling theory, and chapters four to six make the case for a series of requirements, limitations, and principles of application. Chapters seven and eight argue for the value of formal modelling to further flesh out the theory's commitments and potential and describe some simple simulation results which make progress in this regard. Though the inquiry often problematizes the signalling theory, it also shows that it should not be dismissed outright, and that it makes predictions which are apt for empirical testing

A Study of Ethics in Crowd Work-Based Research

Crowd work as a form of a social-technical system has become a popular setting for conducting and distributing academic research. Crowd work platforms such as Amazon Mechanical Turk (MTurk) are widely used by academic researchers. Recent scholarship has highlighted the importance of ethical issues because they could affect the long-term development and application of crowd work in various fields such as the gig economy. However, little study or deliberation has been conducted on the ethical issues associated with academic research in this context. Current sources for ethical research practice, such as the Belmont Report, have not been examined thoroughly on how they should be applied to tackle the ethical issues in crowd work-based research such as those in data collection and usage. Hence, how crowd work-based research should be conducted to make it respectful, beneficent, and just is still an open question. This dissertation research has pursued this open question by interviewing 15 academic researchers and 17 IRB directors and analysts in terms of their perceptions and reflections on ethics in research on MTurk; meanwhile, it has analyzed 15 research guidelines and consent templates for research on MTurk and 14 published papers from the interviewed scholars. Based on analyzing these different sources of data, this dissertation research has identified three dimensions of ethics in crowd work-based research, including ethical issues in payment, data, and human subjects. This dissertation research also uncovered the “original sin” of these ethical issues and discussed its impact in academia, as well as the limitations of the Belmont Report and AoIR Ethical Guidelines 3.0 for Internet Research. The findings and implications of this research can help researchers and IRBs be more conscious about ethics in crowd work-based research and also inspire academic associations such as AoIR to develop ethical guidelines that can address these ethical issues

Revisiting the form and function of conflict: Neurobiological, psychological, and cultural mechanisms for attack and defense within and between groups

Conflict can profoundly affect individuals and their groups. Oftentimes, conflict involves a clash between one side seeking change and increased gains through victory and the other side defending the status quo and protecting against loss and defeat. However, theory and empirical research largely neglected these conflicts between attackers and defenders, and the strategic, social, and psychological consequences of attack and defense remain poorly understood. To fill this void, we model (1) the clashing of attack and defense as games of strategy and reveal that (2) attack benefits from mismatching its target's level of defense, whereas defense benefits from matching the attacker's competitiveness. This suggests that (3) attack recruits neuroendocrine pathways underlying behavioral activation and overconfidence, whereas defense invokes neural networks for behavioral inhibition, vigilant scanning, and hostile attributions; and that (4) people invest less in attack than defense, and attack often fails. Finally, we propose that (5) in intergroup conflict, out-group attack needs institutional arrangements that motivate and coordinate collective action, whereas in-group defense benefits from endogenously emerging in-group identification. We discuss how games of attack and defense may have shaped human capacities for prosociality and aggression, and how third parties can regulate such conflicts and reduce their waste. Keywords: behavioral game theory; biobehavioral approach–avoidance; coevolution of prosociality and aggression; conflict; conflict intervention; cultural institutions; intergroup relations; psychological adaptations