Numerous experiments have shown that people often engage in third-party punishment (3PP) of selfish behavior. This evidence has been used to argue that people respond to selfishness with anger, and get utility from punishing those who mistreat others. Elements of the standard 3PP experimental design, however, allow alternative explanations: it has been argued that 3PP could be motivated by envy (as selfish dictators earn high payoffs), or could be influenced by the use of the strategy method (which is known to influence second-party punishment). Here we test these alternatives by varying the third party’s endowment and the use of the strategy method, and measuring punishment. We find that while third parties do report more envy when they have lower endowments, neither manipulation significantly affects punishment. We also show that punishment is associated with ratings of anger but not of envy. Thus, our results suggest that 3PP is not an artifact of self-focused envy or use of the strategy method. Instead, our findings are consistent with the hypothesis that 3PP is motivated by anger.

There are large individual differences in prosocial vs. antisocial behavior as studied via economic games. Prominent among the personality traits that have been considered as potential correlates are ‘dark’ traits (especially Machiavellianism, Narcissism, Psychopathy, and Sadism). However, although such traits should account for choices in games, the corresponding associations are weak and inconsistent, leading to a state of knowledge that lacks specificity and parsimony. We argue and demonstrate across 10 studies and 8 economic games (total N = 10,474) that a clearer picture emerges once (a) including games that (also) afford the expression of forgiveness (vs. retaliation) and/or (dis)trust and (b) considering the shared vs. unique aspects of dark traits. Specifically, we find that (i) the common core of all dark traits—the dark factor of personality, D—consistently predicts antisocial behavior in all games, (ii) dark traits also (though less strongly) predict antisocial behavior, and (iii) dark traits do so almost entirely due to D. We discuss the theoretical and methodological implications of these findings for the study of individual differences in pro- vs. antisocial behavior in economic games.

Sustainable financial investments play a role in mitigating climate change. With this research, we explored how decision-makers use three investment strategies illustrating different primary motives: (1) money maximization (economic self-interest), (2) exclusion (not personally harming the environment), and (3) inclusion (helping the environment most efficiently). The relative use of these strategies was tested within a novel investment paradigm, aiming to artificially create a trade-off between financial payoffs (money maximization), environmental purity (exclusion), and environmental impact (inclusion). We recruited 1422 participants online and let them make ten consecutive investment choices, with incentivized outcomes, both monetary (i.e., potential bonus payment) and environmental (i.e., number of trees planted). We tested the change in investment choices using a between-subject design with four conditions, a control, and one default condition for each investment strategy. The three strategies were chosen about equally often in the control condition, but we find that this investment pattern could be altered by a default intervention. Preliminary evidence suggests that participants primarily using the exclusion and inclusion strategies differ in their moral reasoning. Utilitarianism better predicted the inclusion strategy, whereas high self-importance of moral identity better predicted the exclusion strategy.

Game riskiness is an index to describe the variance of outcomes of choosing cooperation relative to that of choosing defection in prisoner’s dilemmas (PD). When the variance of cooperation is larger (smaller) than that of defection, the PD is labeled as a more-risky PD (less-risky PD). This article extends the previous work on game riskiness by examining its moderating role on the effect of expectation on cooperation under various PDs. We found across three studies that game riskiness moderated the effect of expectation on cooperation such that the effect of expectation on cooperation was larger in more-risky PDs than in less-risky counterparts. This effect was observed in N-person PD (Study 1), PD presented in both gain and loss domains (Study 2), and PD where expectation was manipulated instead of measured (Study 3). Furthermore, we found that participants cooperated more in PDs presented in the gain domain compared to those presented in the loss domain, and this effect was again moderated by game riskiness. In addition, we illustrated mathematically that game riskiness is related to other established indices of PD, including the index of cooperation, fear index, and greed index. This article identified game riskiness as a robust situational factor that can impact decisions in social dilemmas. It also provided insights into the underlying motivations of cooperation and defection under different expectations and how game riskiness can be utilized in cooperation research.

I introduce the notion of “neglect defaulting,” which labels the propensity to neglect possibilities which are ordinarily sensibly neglected. In familiar contexts we are well-tuned to recognize when to override the default. But outside the range of familiar experience — here in the artificial context of puzzles — these ordinarily benign defaults can make it difficult for even sophisticated subjects, such as readers of this note, to avoid responses which on reflection will be seen as obviously mistaken. A detail of particular importance is that, although subjects are easily prompted to take one step in the direction of reaching a sound response, the tendency to then neglect to consider that another step may be needed is remarkably strong. In each of the five examples the needed but usually neglected second step is quite trivial. Concluding remarks point to consequences for larger questions outside the range of familiar experience, in politics and other contexts out of scale with everyday experience.

Cooperation is a universal phenomenon, it is present in all human cultures from hunter–gatherers to industrialised societies, and it constitutes a fundamental aspect of social relationships. There is, however, variability in the amount of resources people invest in cooperative activities. Recent findings indicate that this variability may be partly explained as a contextually appropriate response to environmental conditions. Specifically, adverse environments seem to be associated with less cooperation and recent findings suggest that this effect is partly mediated by differences in individuals’ life-history strategy. In this paper, we set out to replicate and extend these findings by measuring actual cooperative behaviour in three economic games – a Dictator game, a Trust game and a Public Goods game – on a nationally representative sample of 612 people. Although we found that the cooperation and life-history strategy latent variables were adequately captured by the models, the hypothesised relationship between childhood environmental adversity and adult cooperation and the mediation effect by life-history strategy were not found.

What makes humans moral beings? This question can be understood either as a proximate “how” question or as an ultimate “why” question. The “how” question is about the mental and social mechanisms that produce moral judgments and interactions, and has been investigated by psychologists and social scientists. The “why” question is about the fitness consequences that explain why humans have morality, and has been discussed by evolutionary biologists in the context of the evolution of cooperation. Our goal here is to contribute to a fruitful articulation of such proximate and ultimate explanations of human morality. We develop an approach to morality as an adaptation to an environment in which individuals were in competition to be chosen and recruited in mutually advantageous cooperative interactions. In this environment, the best strategy is to treat others with impartiality and to share the costs and benefits of cooperation equally. Those who offer less than others will be left out of cooperation; conversely, those who offer more will be exploited by their partners. In line with this mutualistic approach, the study of a range of economic games involving property rights, collective actions, mutual help and punishment shows that participants' distributions aim at sharing the costs and benefits of interactions in an impartial way. In particular, the distribution of resources is influenced by effort and talent, and the perception of each participant's rights on the resources to be distributed.