iiinova — where your digital self keeps evolving

Simon Columbus @simoncolumbus.bsky.social · 5h

This week's Cooperation Colloquium: Charles Efferson @charlesefferson.bsky.social The Arbitrary Evolution of Cooperation Date: October 16 Time: 15:00 UTC+2 (Vienna) / 9am NYC Sign up: list.ku.dk/postorius/li...

Abstract: Can we use contemporary empirical results to draw inferences about the evolution of human social behavior? To illustrate the complexities, I examine the evolution of strategies for the repeated play of social dilemmas. Repeated interactions enjoy favorable status as an explanation for the evolution of human cooperation. So favorable, in fact, that one influential hypothesis paradoxically invokes repeated interactions to explain human cooperation in anonymous one-shot experiments. Some studies, however, suggest that repeated interactions in isolation, given a suitably flexible strategy space, do not reliably support cooperation. If generally true, this latter finding would contradict the status of repeated play as a basis for the evolution of both repeated and one-shot cooperation. Using a mix of analytical results and a large simulation project, I consider this question with a social dilemma involving a continuous action space. Under repeated play of such a game, I examine eleven strategy spaces and seven approaches to implementation errors in all 77 combinations. Results show an overall pattern of limited cooperation. In particular, given a combination of strategy space and implementation error that supports the evolution of cooperative strategies, some generalization of the model typically destabilizes cooperation. Although these results do not constitute a general proof, they are consistent with the notion that repeated interactions only support the evolution of cooperation given arbitrary, biologically groundless restrictions on the set of strategies that can arise via mutation or innovation. This finding further implies that an important evolutionary explanation for one-shot cooperation enjoys a privileged status it does not deserve.

011

Simon Columbus @simoncolumbus.bsky.social · 28/09/2026

This week's Cooperation Colloquium: Patricia Kanngiesser @patkanngiesser.bsky.social Sustaining cooperation in intra- and inter-generational resource dilemmas Date: October 2 Time: 15:00 UTC+2 (Vienna) / 9am NYC Sign up: list.ku.dk/postorius/li...

Abstract: The world faces escalating environmental crises that demand cooperation within and across generations. Experimental games provide a testbed for studying sustainable decision-making and cooperation in a safe and controlled environment and for exploring underlying factors. In this talk, I will give an overview of past and ongoing research with children and adults, focusing on inter- and intra-generational sustainability dilemmas. In past work, we have shown that groups of children from two cultures successfully collaborated in a threshold public-goods game using water as a real resource (Kanngiesser et al., 2024). In recent work, we have employed a newly developed harvesting game with a depletable resource to study cooperation across generations of players—specifically, whether participants will adjust their harvesting behaviour and conserve resources better when they know that another, future player will depend on them. I will present new data from both adult participants and cross-cultural child participants on whether they make decisions that benefit themselves and/or future others. For adults, we also explore the role of task framing, cognitive factors (e.g. numeracy), and Social Value Orientation in their decision-making. I will discuss specific challenges of inter-generational collaboration: people might be motivated to benefit future others but might not know how to act to improve their own and others’ outcomes.

016

Simon Columbus @simoncolumbus.bsky.social · 14/09/2026

Our first speaker this week is Kasper Otten (WODC/Erasmus University Rotterdam): The co-occurrence of ingroup and outgroup prosociality across 121 societies Friday, September 18 15:00 UTC+2 (Vienna) / 9am NYT / 21 Beijing Sign up: list.ku.dk/postorius/li...

Abstract: In an increasingly interconnected world, prosociality across group boundaries becomes ever more important. Yet, a common premise in the behavioral and social sciences is that people are prosocial mainly toward their ingroup and not outgroups. So far, evidence for this premise comes mostly from studies in which people must choose between ingroup and outgroup prosociality, thereby precluding positive associations between the two types of prosociality. We study situations in which people make separate decisions regarding the ingroup and outgroup, allowing us to examine how ingroup and outgroup prosociality are related. Across six large-scale and cross-societal datasets spanning 743,402 individuals in 121 societies, we find a robust positive relationship between ingroup and outgroup prosociality. This relationship holds across societies, different group categorizations, and a diverse range of prosociality measures, including prisoner’s dilemmas, public good dilemmas, dictator games, and survey items on trust and tolerance. Although people are somewhat more prosocial toward their ingroup than the outgroup, those who are prosocial toward the ingroup also tend to be prosocial toward the outgroup. The results offer an optimistic message for prosociality across group boundaries. When people are not made to choose between the ingroup and outgroup, they are generally prosocial toward both.

034

Simon Columbus @simoncolumbus.bsky.social · 14/09/2026

Autumn 2026 Cooperation Colloquia We have an exciting interdisciplinary series of speakers with Kasper Otten, @patkanngiesser.bsky.social, @charlesefferson.bsky.social @nikoletaglyn.bsky.social, Cameron Curtin, & Devesh Rustagi Sign up: list.ku.dk/postorius/li...

List of speakers:
2026-09-18 | Kasper Otten (WODC / Erasmus University Rotterdam) | The co-occurrence of ingroup and outgroup prosociality across 121 societies
2026-10-02 | Patricia Kanngiesser (University of Plymouth)
2026-10-16 | Charles Efferson (Université de Lausanne)
2026-10-30 | Nikoleta Glynatsi (RIKEN Center for Computational Science)
2026-11-13 | Cameron Curtin (IAST)
2026-12-11 | Devesh Rustagi (University of Warwick)

1610

Simon Columbus @simoncolumbus.bsky.social · 18/05/2026

A special Cooperation Colloquium this week: Shuxian Jin @shuxianjin.bsky.social The cultural logic of honor in cooperation and punishment across societies Date: Friday, May 22 Time: 15:00 UTC+2 (Vienna) / 9am ET (NYC) Sign up: list.ku.dk/postorius/li...

Abstract: In social interactions, individuals frequently face trade-offs between personal and collective interests, ranging from zero-sum situations — where personal gain may come at others’ expense — to positive-sum situations, where joint efforts lead to mutual benefit. Punishment can sustain cooperation by deterring free riding (prosocial punishment), yet it can also provoke retaliation; when directed at cooperators (antisocial punishment), punishment may even undermine collective welfare. In this talk, I will present two cross-cultural studies examining the role of the cultural logic of honor in shaping how individuals navigate these tensions and adopt particular punishment strategies in situations involving conflicts of interest. Drawing on a 13-society online behavioral experiment (n = 3,371), we found that perceived societal norms of honor were associated with greater competition in zero-sum situations, but also greater coordinative efforts in positive-sum situations at both individual and societal levels. In a multi-lab experiment conducted in Egypt (n = 266), South Korea (n = 212), and the UK (n = 192), we found that honor values and norms were not directly associated with engagement in prosocial or antisocial punishment. However, when individuals experience unfair treatment, honor values and norms intensified antisocial retaliatory responses. Together, these studies show how honor, as a relatively understudied cultural construct, helps explain variation in cooperation and punishment across societies.

052

Simon Columbus @simoncolumbus.bsky.social · 04/05/2026

This week's Cooperation Colloquium: Sebastian Hafenbrädl @shafenbraedl.bsky.social Social rewards protection theory: Why people morally derogate prosocial actors for undisclosed personal benefits Date: May 8 Time: 15:00 UTC+2 (Vienna) / 9am ET (NYC) Sign up: list.ku.dk/postorius/li...

Abstract: Prosocial behavior is common and often socially rewarded (e.g., via liking, status, and trust). Yet prior research has found that if actors themselves also benefit from their prosocial behavior, then they are morally derogated: They are evaluated as worse than purely selfish actors. This tainted-altruism effect has been explained by the use of different counterfactuals for the evaluation of prosocial and selfish actors. Here I propose social rewards protection theory, which explains why evaluators use these different counterfactuals in the first place: Social rewards are treated as being reserved for costly prosocial actions. Claiming such rewards without incurring costs seems like cheating and thus deserves moral derogation. Accordingly, being transparent about the action’s costs and benefits prevents such derogation. I conducted six experiments (five preregistered) with Amazon Mechanical Turk (MTurk) workers in the United States and lab participants in Spain (total N = 4,732 adults). The findings provide support for the proposed functional explanation of tainted altruism, which also sheds light on related phenomena, such as overhead aversion and hypocrisy.

022

Simon Columbus @simoncolumbus.bsky.social · 20/04/2026

This week's Cooperation Colloquium: Aron Szekely @aronszekely.bsky.social Measuring social norms with surveys Date: Friday, April 24 Time: 15:00 UTC+2 (Vienna) / 9am ET (NYC) Sign up: list.ku.dk/postorius/li...

Abstract: Accurately measuring social norms is crucial both for explaining cooperation and prosociality and for designing effective policy measures that support these. While established laboratory-based approaches represent “gold-standard” approaches, their practicality and widespread use are limited by the restrictions involved in their implementation. In contrast, non-incentivised survey measures are simple and widely used yet remain unvalidated, leaving it unclear what they truly capture. We address this gap by validating a popular set of non-incentivised measures against incentivised benchmarks across two diverse contexts—one WEIRD (Italy) and one non-WEIRD (India)—using student and general-population samples (N≈1,400) in laboratory and lab-in-the-field environments. Every measure is validated in seven settings representing a range of interaction domains including cooperation (e.g. Public Goods Game, Dictator Game). From these results, we assemble a menu of validated survey measures, highlighting their respective strengths and offering guidance for best practice across different research contexts and constraints.

032

Simon Columbus @simoncolumbus.bsky.social · 06/04/2026

This week's Cooperation Colloquium: Saptarshi Pal (Harvard) From simultaneous to leader-follower play in direct reciprocity Date: April 10 Time: 15:00 UTC+2 (Vienna) / 9am ET (NYC) Sign up here: list.ku.dk/postorius/li...

Abstract: Repeated interaction is a key mechanism driving the evolution of cooperation, generosity, extortion, and other social behaviors. These behaviors are typically studied using two-player repeated games, where the two players act simultaneously in every round. In this paper, we begin with a standard two-action repeated game, but transform it into a leader–follower game. We do this by forcing one player to indicate their impending move, or to openly commit first in each round. We show that this simple transformation provides new and useful analytical insights. In particular, we use this transformation to derive expressions for the main classes of simultaneous-move Nash equilibria of memory-1, when payoffs are discounted. We show that these equilibria also remain stable under the leader–follower structure. We prove that this reassuring property does not always extend to games with more than two actions or to equilibrium strategies with longer memory. Overall, we establish a novel connection between repeated simultaneous-move games and repeated leader–follower games in evolutionary game theory. This approach offers fruitful means of investigating how prediction and anticipation play a role in stable social behavior.

052

Simon Columbus @simoncolumbus.bsky.social · 23/03/2026

This week's Cooperation Colloquium: Minhua Yan @minhuayan.bsky.social @iast.fr The persistence and adaptation of social norms: Theory and field evidence Date: March 27 Time: 15:00 UTC+1 (Vienna) / 10 am ET (NYC) Sign up: list.ku.dk/postorius/li...

Abstract: Social norms are unwritten rules that guide human behavior and social interaction. They play a central role in promoting cooperation and maintaining cultural diversity. Yet because norms pressure people to do what others do, they may also sustain practices that are inefficient or harmful. In this talk, I present insights from a mathematical model and a field study that together examine whether and how such norms can persist. The model challenges the idea that arbitrary or harmful norms can be maintained solely through social pressure. It shows that norms with continuously varying behavioral options cannot be maintained at ecologically or psychologically suboptimal equilibria, suggesting that norms adapt more readily than previously assumed. I then present evidence from a field study among the Derung, small-scale horticulturalists in Yunnan, China. Derung farmers continued to follow a traditional cooperative farming harvest division norm after market integration. They did so even though they recognized its lower ecological payoff and expected no social disapproval for deviating from it. Rather than payoff calculations, Derung farmers adhered to the norm out of a desire to follow tradition and common practice. However, five years later the norm had changed, consistent with the model’s prediction that norms with continuously varying options eventually adapt to ecological conditions.

053

Simon Columbus @simoncolumbus.bsky.social · 09/03/2026

Cooperation Colloquium this week: Manon Schweinfurth @standrewspsyneuro.bsky.social Pathways to reciprocal cooperation across taxa Date: March 13 Time: 15:00 UTC+1 (Vienna) / 10 am ET (NYC) Sign up: list.ku.dk/postorius/li...

Abstract: If only those behaviours evolve that increase the actor’s own survival and reproductive success, then it might come as a surprise that cooperative behaviours, i.e., providing benefits to others, are a widespread phenomenon. One possibility to explain these behaviours is reciprocal cooperation, i.e., helping those that were helpful before. Still, the evolutionary origin of it is largely unclear, mainly because it is believed that - in contrast to humans - other animals do not exchange help reciprocally. Yet, I propose that reciprocity is likely to be widespread. In my talk, I will first shed light on the mechanisms of reciprocal cooperation in Norway rats (Rattus norvegicus). In a series of studies, my colleagues and I have demonstrated that Norway rats reciprocally exchange goods and services between and within different commodities and that reciprocal cooperation is not necessarily cognitively demanding. Furthermore, to understand the evolutionary origins of human reciprocity, and whether it is shared with other animals, I will then discuss evidence for reciprocity in non-human primates, which are our closest living relatives. A thorough analysis of the findings showed that reciprocity is present and not confined to unrelated individuals. Based on my findings, I conclude that reciprocal cooperation in non-human animals is present but largely neglected and not restricted to humans.

002

Simon Columbus @simoncolumbus.bsky.social · 23/02/2026

Cooperation Colloquium this week: Taylor Kessinger (U Penn): Adaptive dynamics of reputation, social norms, and gossip Date: Feb 27 Time: 15:00 UTC+1 / 9 am ET Sign up: list.ku.dk/postorius/li...

Abstract: Human societies are characterized by large-scale cooperative behavior, even among unrelated strangers. Why? One plausible answer is indirect reciprocity: If I help a stranger, I might gain a good reputation, increasing the likelihood that others will help me in turn. But under what circumstances can indirect reciprocity facilitate a stable, cooperative status quo? Can these circumstances—for example, a high level of agreement about reputations—evolve in the first place? For that matter, what rules for assigning reputations can evolve? I use adaptive dynamics to attain simple, intuitive answers to these questions. Specifically, I study the evolution of cooperative strategies, gossiping behavior, and even moral assessment rules themselves by parametrizing them as continuous traits. I confirm some classical results in the theory of indirect reciprocity but challenge others. Cooperation is easily sustainable, provided reputational views are sufficiently correlated. But when reputations are a matter of private judgment, there are no stable cooperative equilibria at all. Gossip can facilitate a high level of agreement, but echo chambers are difficult to overcome. Crucially, while many assessment rules can facilitate cooperation, almost none of them can actually evolve. The main exception is Stern Judging, which mandates that bad individuals be punished––a rule that is, sadly, highly intolerant of disagreement. I conclude by discussing implications for polarization, moral philosophy, and the discourse. Adaptive dynamics provides a mathematical framework not only for establishing a baseline theory of indirect reciprocity but also for incorporating the foibles and peculiarities of real human societies.

002

Simon Columbus @simoncolumbus.bsky.social · 09/02/2026

Cooperation Colloquium this week: Yan Chen @yanchenl.bsky.social Digital public goods: Crowdsourcing, crowdfunding and user-generated content Date: February 13 Time: 15:00 UTC+1 (Vienna) / 9 ET (NYC) Sign up: list.ku.dk/postorius/li...

Abstract: What motivates people to contribute to Wikipedia? Have you heard of Nupedia? Why do software engineers contribute code to open source projects? Why do technology companies release their large language models as "open weight"? Why has participation declined on Stack Overflow since the release of ChatGPT, but not on the programming subreddit? Why do some crowdfunding sites succeed while others fail? Underlying each of these questions is a more fundamental one: how can social scientists, computer and information scientists and practitioners use social science theories combined with information technology to increase contributions to public goods? To explore this question, my book, "Digital Public Goods", introduces (1) case studies from the technology sector to set up the problems; (2) social science theories of motivation, production, informational nudges, identity and teams, goal setting, and reputation, together with their field implementations using information technologies, as solutions; and (3) experimental evaluations of these theories and solutions. The goal of this book is to merge the latest research in the scholarly literature with successful practices used by digital platforms to provide scholars, students and practitioners with the intellectual tools they need to develop an understanding of digital public goods provision.

051

Simon Columbus @simoncolumbus.bsky.social · 27/01/2026

First Cooperation Colloquium of the year: Caroline Graf (University of Zürich): Boosting prosocial behavior through incentives and conditional giving: Experimental evidence from 42 societies Friday, January 30 | 15:00 UCT+1 Vienna / 9:00 ET NYC Sign up: list.ku.dk/postorius/li...

Abtract: Prosocial behavior is key to addressing global collective-action challenges. Two prominent tools to promote prosociality are incentives and the use of conditional preferences, yet existing evidence is mixed and largely based on WEIRD populations. We study how incentives and conditionality shape prosocial behavior across diverse cultural contexts, and how cultural characteristics moderate these effects. 15,600 participants from 42 countries completed an online experiment in which prosociality was measured as the donation of earned bonus points to international charities (e.g., UNICEF). In the incentive condition, donors received additional points worth half of the donated amount. In the conditionality treatment, participants could condition their donation on the share of other donors in their country. Preregistered analyses show that incentives increase prosocial behavior overall, but that their effectiveness varies across societies. Incentive effects are stronger in societies where the reputational costs of benefiting personally from prosocial acts are lower, that is, where incentivized donors are perceived as relatively more likable. Conditional giving also increases prosocial behavior, yet the effects are larger in societies characterized by a higher prevalence of conditional preferences and stronger generalized fairness concerns. Together, these findings highlight that the effectiveness of behavioral interventions depends systematically on cultural context, underscoring the importance of moving beyond WEIRD samples not only for advancing theory, but also for culturally tailored policy design.

055

Simon Columbus @simoncolumbus.bsky.social · 01/12/2025

This week's Cooperation Colloquium: Alex Mesoudi @alexmesoudi.com Experimental evidence that reputation-based partner choice facilitates information sharing in humans Date: December 5 Time: 15:00 UTC+1 (Vienna) / 9 am ET (NYC) Sign up: list.ku.dk/postorius/li...

Abstract: A necessary prerequisite for the accumulation of beneficial knowledge, or ‘cumulative cultural evolution’, is the sharing of information via social learning. Yet little work in the field of cultural evolution has examined the mechanisms that support information sharing in the face of exploitative information free-riding and information hoarding. We ran a series of online interactive experiments (N = 716) combined with computational reinforcement and social learning models to test whether the mechanism of reputation-based partner choice can effectively support information sharing. Participants in groups chose whether to (i) engage in costly innovation and (ii) whether to share the resultant knowledge. Sharers received increased reputations for sharing and participants could use reputations to select recipients of knowledge. Study 1 found, in participants from the UK and China, high levels of information sharing but only weak partner choice. Study 2 replicated this finding with various methodological improvements. Study 3 showed that participants used partner choice to exclude non-sharing artificial bots from receiving information. Study 4 found that when partner choice was impossible, preferences for information sharing declined to levels comparable to non-sharing. Overall, our findings provide tentative positive experimental evidence that partner choice can facilitate information sharing and enable cumulative cultural evolution.

0136

Simon Columbus @simoncolumbus.bsky.social · 17/11/2025

Cooperation Colloquium this Friday: Kristopher M. Smith @kris-smith.bsky.social Long-distance friends and collective action in fisheries management Date: Friday, November 21 Time: 16:00 UTC+1 / 10 am NYC (one hour later than usual!) Sign up: list.ku.dk/postorius/li...

Abstract: The management of shared natural resources often hinges on local cooperation, yet the social networks linking communities across space can both complicate and enable collective action. This talk examines how long-distance friendships—relationships that bridge community boundaries—shape trust, cooperation, and participation in fisheries management in coastal Tanzania. Drawing on theoretical models and multi-site ethnographic and survey data from the Tanga Sociality and Fisheries Project, I show that long-distance friendships provide key forms of material support similar to local friendships, suggesting they are a resilient social strategy for managing ecological and economic risk while fostering interdependence across villages. In turn, people with more long-distance friends express greater trust in non-local partners and are more likely to engage in collective monitoring and reporting of destructive fishing practices. Finally, I introduce a new measure, “long-distance orientation,” capturing individual variation in the motivation and capacity to form and sustain these ties, highlighting psychological and structural factors that facilitate cooperation at a distance. Together, these findings suggest that long-distance relationships can serve as a foundation for scaling up collective action and designing management systems that bridge community boundaries.

031

Simon Columbus @simoncolumbus.bsky.social · 03/11/2025

Cooperation Colloquium this week: Terence Dores Cruz (University of Amsterdam) The costs and benefits of gossip in reputation-based cooperation Date: Friday, November 7 Time: 15:00 UTC+1 (Vienna) / 9am NYC Sign up: list.ku.dk/postorius/li...

Abstract: Gossip is an ever-present feature of our social interactions. We gossip to update one another about the others in our social environment. Our persistent gossip shapes perceptions and behaviors that are key to forming, keeping, and severing social relationships. These uses of gossip have given rise to the perspective that gossip has cooperative functions. This entails that people gossip to provide information about how to (not) behave and who can(not) be trusted to cooperate. This informs people about others’ reputations, which can serve to make better decisions about whom to cooperate with and whom to avoid. First, I will present research that supports this perspective based on experience sampling, scenario studies, and behavioral experiments. I find that people use reputational information provided by gossip to shape how they think about the targets of gossip. These gossip-based impressions guide receivers’ cooperative behavior toward targets: they cooperate with people they learn are likely to be cooperative and avoid people who they learn are likely to violate norms. Second, I focus on the puzzle of gossip as key for a cooperative social life while also being commonly perceived very negatively. Gossip is needed but could lead to costs for gossipers that motivate refraining from gossip. Based on ongoing research using behavioral experiments, I will present the first steps towards understanding the puzzle of the costs and benefits of gossip. Receivers of gossip support gossip systems by punishing harm to the reputation-system from not contributing gossip or spreading false information and by rewarding accurate gossip.

021

Simon Columbus @simoncolumbus.bsky.social · 21/10/2025

This week's Cooperation Colloquium: Christian Ruff @ccruff.bsky.social Neurocomputational mechanisms of mentalizing in social interaction When: October 24, 15:00 UTC+2 (Vienna) / 9am NYC Sign up: list.ku.dk/postorius/li...

Abstract: Successful cooperation depends on mentalization—the ability to infer and adapt to others’ beliefs, intentions, and strategies. Yet, most existing studies and models treat mentalizing as a static trait rather than an adaptive, dynamic process unfolding within interactive contexts. In this talk, I will present a modelling framework and experimental paradigm that capture adaptive mentalization: the capacity to continuously update one’s internal model of another person’s behavioral sophistication and to adjust one’s own strategy accordingly. Using a social strategic game combined with computational modeling and fMRI, we develop and validate a Bayesian model indexing how effectively individuals can adapt their mental models in response to changing partner behavior, and we identify a multivariate neural signature that can predict this adaptiveness of mentalization. This neural pattern generalizes across individuals and closely tracks the flexibility of mental-state inference during interaction. Applying this paradigm to individuals with varying levels of autistic traits, we find that reduced adaptive mentalization —both behaviorally and neurally—correlates with higher trait expression. These results reveal how subtle alterations in the adaptiveness of mentalization can influence the dynamics of social interactions. By grounding social interaction in formal models of belief-updating and strategy adjustment, our work advances a more mechanistic understanding of how humans coordinate minds in social contexts—and how individual differences in these computations shape social behavior.

021

Simon Columbus @simoncolumbus.bsky.social · 06/10/2025

This week's Cooperation Colloquium: Setayesh Radkani @setayeshradkani.bsky.social: What people learn from punishment: A cognitive model Date: Friday, Oct 10 Time: 15:00 UTC+2 Vienna / 9 am NYC Sign up: list.ku.dk/postorius/li...

Abstract: Authorities, from parents of toddlers to leaders of formal institutions, use punishment to communicate disapproval and enforce social norms. However, punishment is often interpreted in contrasting ways: at times it teaches and enforces norms, but at other times it fails or even backfires, undermining the authority’s legitimacy. We show that these seemingly contradictory effects of punishment can only be understood by considering the cognitive processes in the minds of human observers of punishment. In a series of experiments, we showed the systematic variability in how adults and children interpret punishment. We developed a formal cognitive model, derived from a standard model of how people make sense of each others’ actions (Inverse Planning), that captures and explains these inferences quantitatively and parsimoniously. This work reveals the rational logic behind how people learn from punishment, and a key constraint on the function of punishment in establishing shared social norms.

052

Simon Columbus @simoncolumbus.bsky.social · 22/09/2025

Cooperation Colloquium this week: Talbot M. Andrews @talbotmandrews.bsky.social (Cornell): Overcoming the social dilemma of climate change Friday, Sep 26, 15:00 UTC+2 Vienna / 9 am NYC Sign up: list.ku.dk/postorius/li...

Abstract: Mitigating the increasing threat of climate change poses a uniquely challenging cooperative problem. Multiple strategic features of climate change impede coordinating around successful action. For example, there is uncertainty about the timing and dynamics of climate change impacts. Different actors vary in their historic contribution to the problem and vulnerability now. There are many solutions available to mitigate climate change, but they differ in their effectiveness and probability of success. And, compounding all of this, there are asymmetries in information between elite decision-makers and the publics that they govern. In this talk, I argue economic games are well-suited to understand both how these strategic features delay successful climate action and provide insights into how to overcome these problems through public policy. Focusing on the case of governing emerging mitigation technologies, I will present the empirical evidence that people are willing to pay costs to avert climate disaster. While mistrust between the public and policymakers erodes cooperation, I will also present solutions that emerge from these experiments. I conclude by discussing how insights from the lab can inform real-world messaging and policymaking to encourage successful climate change mitigation.

063

Simon Columbus @simoncolumbus.bsky.social · 21/09/2025

Spent a few lovely days at the Matterhorn Symposium in Brig 🇨🇭, where I presented joint work with @mkasper.bsky.social and others on biased institutions. Next stop: Kassel for #DPPD25 and a talk on our new scale for HEXACO personality states.

A view from a Swiss alp near the Aletsch Glacier towards the Matterhorn.

180

Simon Columbus @simoncolumbus.bsky.social · 08/09/2025

First Cooperation Colloquium of the semester! Doruk İriş @dorukiris.bsky.social: Normative expectations of reciprocal negotiators Friday Sep 12, 14:00 UTC+2 (Vienna) / 8 am NYC Sign up: list.ku.dk/postorius/li...

Abstract: This paper develops a theoretical framework to examine how normative expectations--what one considers others should do based on their fairness perceptions--in shaping the behavior of players with reciprocal preferences in a public goods game. Standard reciprocity models typically assume uniform, exogenously determined, and moderate expectations. By contrast, I allow players to (i) vary in how demanding they are of others, (ii) disagree about what counts as fair, and (iii) form self-centered normative expectations endogenously. In noncooperative play, strong reciprocal concerns transform the payoff structure from a material payoff dilemma into a coordination game in utilities, with one exception. In coalition formation, three central results emerge: (i) the empty coalition is always stable, (ii) the grand coalition becomes stable once reciprocal concerns are sufficiently strong, and (iii) partial coalitions can be stable under specific conditions. Exogenous expectations create distinct effects on cooperation: lower expectations facilitate the stability of the grand coalition, whereas higher expectations increase the size of partial coalitions, potentially leading to a majority coalition. This latter finding is more consistent with empirical observation.

071

Simon Columbus @simoncolumbus.bsky.social · 31/08/2025

Off to Vienna 🇦🇹 on this lovely Dundee morning

040

Simon Columbus @simoncolumbus.bsky.social · 29/08/2025

Okay, this is officially my favourite figure: From www.sciencedirect.com/science/arti...

130

Simon Columbus @simoncolumbus.bsky.social · 28/08/2025

Trade offer? Extortion by the seagull mafia?

A photo of a fish on a balcony. *My* balcony.

Another photo of a fish on a balcony. Still my balcony.

240

Simon Columbus @simoncolumbus.bsky.social · 26/08/2025

⚡ Autumn 2025 Cooperation Colloquia ⚡ We are excited to announce the next run of Cooperation Colloquia. With @talbotmandrews.bsky.social, @setayeshradkani.bsky.social, @kris-smith.bsky.social, @alexmesoudi.com, & more. Every second Friday, 15:00 CE(S)T Sign up here: list.ku.dk/postorius/li...

Speaker list for the Autumn 2025 Cooperation Colloquia:
2025-09-12 | Doruk İriş (Sogang University)
2025-09-26 | Talbot M. Andrews (Cornell University)
2025-10-10 | Setayesh Radkani (MIT)
2025-10-24 | Christian Ruff (University of Zürich)
2025-11-07 | Bianca Beersma (Vrije Universiteit Amsterdam)
2025-11-21 | Kristopher M. Smith (Washington State University)
2025-12-05 | Alex Mesoudi (University of Exeter)

088

Simon Columbus @simoncolumbus.bsky.social · 26/08/2025

Yup, and here's the third paper, also in Ecological Indicators

310

Simon Columbus @simoncolumbus.bsky.social · 18/08/2025

For the last few weeks, Cecilie Strandsbjerg from @cphsodas.bsky.social visited me at St Andrews as part of a project on developing new personality scales for experience sampling studies. To round off the visit, we went for a coastal hike with @qinyuxiao.bsky.social, who's visiting from Vienna.

Two people standing between the pillars of Buddo Rock, a sandstone rock on the coast of Fife near St Andrews.

171

Simon Columbus @simoncolumbus.bsky.social · 08/08/2025

Before they go on the shelves: all physical books I've acquired since I last had access to my library two years ago.

110

Simon Columbus @simoncolumbus.bsky.social · 17/07/2025

Already on the 'right' side ;-) Usually Mana for coffee or Espresso Lab to write. How does tomorrow look?

110

Simon Columbus @simoncolumbus.bsky.social · 02/06/2025

Join us on Friday for the last Cooperation Colloquium of the semester: Fernando P. Santos @fernandopsantos.bsky.social Cooperation and indirect reciprocity in human-AI systems Date: June 6 Time: 15:00 UTC+2 (Vienna) / 9 am NYC Sign up: list.ku.dk/postorius/li...

Abstract: Indirect reciprocity is a key mechanism to understand the evolution of cooperation among unrelated individuals. By helping someone, individuals may improve their reputation, which may be shared in a population and change the predisposition of others to reciprocate in the future. The reputation of individuals depends, in turn, on social norms that define a good or bad action. Over the years, theoretical and empirical research has unveiled many features of cooperation under IR, exploring norms with varying degrees of complexity and information requirements. Often, however, it is assumed that 1) reputations spread for free, 2) individuals can adopt arbitrarily complex norms and 3) populations are fully composed by homogeneous individuals. In this presentation, I will discuss a way to quantify the complexity of norms and strategies in indirect reciprocity and the challenges introduced by complex rules and costly reputation sharing. We will observe that cooperation can prevail with simple norms and costly reputation sharing, provided that individuals can anticipate the reporting intentions of their opponents. I will conclude by discussing the potential of indirect reciprocity to sustain cooperation in populations that include both humans and artificial agents.

063

Simon Columbus @simoncolumbus.bsky.social · 19/05/2025

This weeks's Cooperation Colloquium: Catherine Molho @cmolho.bsky.social Guilt drives prosocial behavior across countries Date: May 23 Time: 15:00 UTC+2 (Vienna) / 9 am ET (NYC) Sign up: list.ku.dk/postorius/li...

Abstract: Influential theories have proposed that impersonal prosociality varies across human societies. At the same time, different societies may rely on distinct mechanisms—guilt and internalized norms versus shame and external pressures—to promote prosocial behavior. We examine these mechanisms in a pre-registered experiment with 7,978 participants across 20 culturally diverse countries. Participants made monetary allocation decisions between themselves and strangers. To examine how guilt and shame affected prosociality, we introduced two variations to this standard decision-making task. First, to activate guilt, we varied information about the consequences of participants’ decisions (full versus hidden). Second, to activate shame, we varied the observability of participants’ decisions (public versus private). Additionally, we measured guilt- and shame-proneness at the individual and country levels. We find robust evidence for guilt-driven prosociality and willful ignorance across all countries. Allowing individuals to avoid information about the consequences of their actions substantially decreases prosociality. Guilt-prone, rather than shame-prone, individuals are more responsive to the presence of information about the negative consequences of their actions. In contrast, we find that making decisions observable among strangers has negligible effects on prosociality. Our study provides a first comprehensive investigation of how guilt and shame affect prosociality around the world.

0103

Simon Columbus @simoncolumbus.bsky.social · 12/05/2025

Learned from David Edmonds' Vienna Circle biography 'The Murder of Professor Schlick' that Otto Neurath would sign his letters with a drawn elephant. How cool is that?!

210

Simon Columbus @simoncolumbus.bsky.social · 05/05/2025

Cooperation Colloquium this week: Ro'i Zultan @rzultan.bsky.social Perceptions of intergroup conflict Date: May 9 Time: 15:00 UTC+2 / 9 am NYC Sign up: list.ku.dk/postorius/li...

Abstract: In Weisel and Zultan (2016, 2021a, 2021b, 2022), we claim that whether intergroup conflict is perceived as a threat to the individual or to the group informs the behavioral responses to conflict. In this talk, I will provide an overview of this research program, and share some background and ruminations beyond the information contained in the published papers.

011

Simon Columbus @simoncolumbus.bsky.social · 02/05/2025

Made it to Scotland for my new position with @standrewspsyneuro.bsky.social. Here's last night's view from the guest room -- suppose I can get used that.

3150

Simon Columbus @simoncolumbus.bsky.social · 22/04/2025

This week's Cooperation Colloquium: Hisashi Ohtsuki (SOKENDAI) Evolutionary models of human cooperation; kin and reciprocation Date: April 25 Time: 14:00 UTC+2 / 8 am NYC (one hour earlier than usual!) Sign up: list.ku.dk/postorius/li...

Abstract: Evolutionary theories have revealed various mechanisms that promote cooperation in biological organisms, and humans are no exceptions. The modern theory classifies those mechanisms into two major categories: one is kin selection, and the other is reciprocity. Kin selection means that the benefit of cooperation is passed to a relative who shares the same gene and therefore a gene that encodes cooperation is favored by natural selection. Reciprocity means that the benefit of cooperation is later given back to the cooperator in a reciprocal manner. In this talk, I will talk about those two mechanisms and how they can explain the evolutionary origin of human cooperation. First, I discuss a game-theoretic model that hypothesizes that modern human cooperation has its origin in our ancestral time when kin selection strongly operated. Second, I will talk about indirect reciprocity, which is reputation-based cooperation, and explain my recent theoretical finding that reciprocal cooperation can be robustly maintained even if reputation information is not public.

010

Simon Columbus @simoncolumbus.bsky.social · 07/04/2025

"pre-registration has now become mainstream in experimental economics" New preprint by Taisuke Imai et al.: osf.io/preprints/me...

Abstract: The open science movement has gained significant momentum over the past decade, with pre-registration and the use of pre-analysis plans being central to ongoing debates. Combining observational evidence on trends in adoption with survey data from 519 re-searchers, this study examines the adoption of pre-registration (potentially but not necessarily including pre-analysis plans) in experimental economics. Pooling statistics from 19 leading journals published between 2017 and 2023, we observe that the number of papers containing a pre-registration grew from seven per year to 190 per year. Our findings indicate that pre-registration has now become mainstream in experimental economics, with two-thirds of respondents expressing favorable views and 86% having pre-registered at least one study. However, opinions are divided on the scope and comprehensiveness of pre-registration, highlighting the need for clearer guidelines. Researchers assign a credibility premium to pre-registered tests, although the exact channels remain to be understood. Our results suggest growing support for open science practices among experimental economists, with demand for professional associations to guide researchers and reviewers on best practices for pre-registration and other open science initiatives.

0112

Simon Columbus @simoncolumbus.bsky.social · 07/04/2025

This week's Cooperation Colloquium: Andreas Glöckner (University of Cologne) Modeling social preferences in cross-national interactions Date: April 11 Time: 15:00 UTC+2 Vienna / 9 am NYC Sign-up: list.ku.dk/postorius/li...

Abstract: When making decisions, individuals do not only take into account their own payoffs but often additionally consider the consequences for others. Models of social preferences (e.g., social value orientation) aim to describe exactly how outcome for the self and for others are integrated. Models widely differ concerning whether and how various factors are taken into account. They contain for example different relative weights for the own and the other outcome, take into account inequality (i.e. differences in outcomes for self and other) and/or efficiency concerns (i.e. the sum of outcomes). Some models, such as Jenkins et al. (2018), also differentiate between cases of advantageous and disadvantageous inequality. Jenkins et al. suggested a Social Perception-Weighted (SPW) model of social valuation, which takes into account perceived competence and warmth from the stereotype content model and show its superiority in predicting behavior. We conduct a comprehensive model comparison by (i) applying SPW to cross-national interactions, (ii) testing SPW against competing models, and (iii) extending SPW by including further variables. We analyze choices from an incentivized, multi-national study (N = 6,182). In the experiment, individuals from 25 nations allocated money between themselves and individuals from the own and each other nation. Stereotype perception, perceived conflict between nations and further factors were measured. Based on these model comparisons, we identify relevant structures and factors and suggest an extended model of social preference for cross-national interactions taking into account social perception.

032

Simon Columbus @simoncolumbus.bsky.social · 31/03/2025

Next Cooperation Colloquium *this week*: Astrid Dannenberg (University of Kassel) The willingness to intervene in socially harmful behavior Date: April 4 Time: 15:00 UTC+1 / 9 am NYC / 21:00 Beijing Sign up: list.ku.dk/postorius/li...

Abstract: Whether people actively intervene in socially harmful behavior, which factors predict this decision, and whether the decision can be influenced has been little studied so far. Here, we investigate these questions using the example of cigarette littering, a behavior that is ecologically, economically, and socially harmful, yet widespread. The results, which are based on a survey experiment combined with field experimental investigations from Germany, show that the willingness to intervene is generally rather low, especially when the litterer is a stranger, people lack intrinsic motivation, are accustomed to cigarette littering, and do not have small children. Expectations about how approached litterers may react do not predict the intervention decision. We also find that the willingness to intervene is fundamentally different from the willingness to pay for a public awareness campaign that calls on others to intervene. These two decisions are not correlated and they differ in their predictors and their responsiveness to appeals or the provision of information.

010

Simon Columbus @simoncolumbus.bsky.social · 24/03/2025

Upcoming Cooperation Colloquium: Alexander J. Stewart @al-cibiades.bsky.social Evolution of cultural tightness under descriptive and injunctive norms Date: Friday, March 28 Time: 15:00 UTC+1 (Vienna) / 10 am NYC Sign up: list.ku.dk/postorius/li...

Abstract: We study the coevolution of behavior, expressed beliefs and social preferences in a population engaging in pairwise cooperation through either a snowdrift game or a prisoner’s dilemma. We assume that individuals derive utility partially through the material payoff from cooperation, and partially through “norm-utility” (see e.g. Gavrilets et al, Phil Trans B, 2024), which captures the psychological benefit of adherence to or deviation from perceived social norms. In particular we explore the differences between the evolution of a population adhering to descriptive norms (derived from beliefs about what others actually do) as opposed to injunctive norms (derived from beliefs about what others should do). We identify a surprising trade-off, in which descriptive norms tend on average to promote greater cultural tightness (i.e. the existence of norms which are widely understood and adhered to), while at the same time disrupting social cohesion. Specifically, a shift from injunctive to descriptive norms facilitates evolutionary branching, in which the population splits into two groups who not only behave differently, but also possess different social preferences.

033

Simon Columbus @simoncolumbus.bsky.social · 10/03/2025

Cooperation Colloquium this week: Louis Putterman (Brown University) The linkage of second-order to first-order collective action problems as a lever facilitating cooperation Date: Friday, March 14 Time: 15:00 UTC+1 (Vienna) / 10 am NYC Sign up: list.ku.dk/postorius/li...

001

Simon Columbus @simoncolumbus.bsky.social · 24/02/2025

Cooperation Colloquium this week: Ingela Alger (@ingelaalger.bsky.social) On the co-existence of morality and spite: Evolutionary theory and experimental evidence Friday Feb 28, 15:00 UTC+1 (Vienna) / 9 am NYC Sign up: list.ku.dk/postorius/li...

Abstract: There is by now a considerable amount of theoretical research on the evolutionary foundations of human motivation, or preferences. In the first part of this talk I will present a result which points to a particular class of preferences, which under general conditions combines a certain kind of pro-social concern (a Kantian moral concern) with a certain kind of anti-social concern (spite). The result further suggests that these two motivations go hand in hand. In the second part I will present experimental evidence based on simple designs that enable disentangling these motivations.

043

Simon Columbus @simoncolumbus.bsky.social · 31/01/2025

Cooperation Colloquium today: Sarah Brosnan (Georgia State University) Understanding primate cooperating using experimental games 15:00 UTC+1 Vienna / 9 am NYC Sign-up for link: list.ku.dk/postorius/li...

012

Simon Columbus @simoncolumbus.bsky.social · 27/01/2025

Our first speaker will be Sarah Brosnan (Georgia State University) Understanding primate cooperation using experimental games Friday, Jan 31 15:00 UTC+1 (Vienna) / 9 am NYC

001