Jaromír Kovářík

Collective action problems emerge when individual incentives and group interests are misaligned, as in the case of climate change. Individuals involved in these problems are generally considered to have two options: contribute toward public solutions such as global warming mitigation or free ride. However, many collective action problems today involve a third option of investing in a “private solution” such as local adaptation. The availability of this third option can lead to a private solution trap whereby private solutions are adopted, collectively optimal public solutions are not provided, and existing inequalities are exacerbated. We investigated the private solution trap with a collective action game featuring private and public solutions, wealth inequality determined by luck or merit, and participants from 34 countries. We found that the joint existence of private solutions and wealth inequality had a consistent effect across countries: Participants given a higher endowment adopted private solutions almost twice as often as those given a lower endowment, regardless of whether it was determined by luck or merit, and contributed proportionally less toward public solutions. Wealth inequality increased in every country and those given lower endowments were often left unprotected as public solutions were not provided. Across countries, cultural values of hierarchy and harmony were associated with preferences for private and public solutions, respectively. We also identified two universal pathways toward public solution provision: early contributions and conditional cooperation. Our findings highlight the ubiquity of the private solution trap, its cultural underpinnings, and its potential consequences for global collective action problems.

This study explores how individuals perceive their social networks, with a focus on their own positioning. Using experimental methods and network analysis, we show that people have a limited understanding of their social standing in terms of popularity (in-degree) and centrality. Few participants accurately estimate their popularity, and even fewer correctly identify their decile of centrality. A similar pattern emerges for their perceptions of the most popular and central individuals, but we find no correlation between the ability to assess one’s own position and the ability to detect key network members. Popular participants correctly perceive themselves as more popular, although they tend to misjudge their popularity more than less popular peers. They are nonetheless more accurate in estimating their centrality. Perceived centrality is only weakly correlated with actual centrality, but central individuals misperceive both their popularity and centrality to a greater extent. We further show that these misperceptions have real-world implications. Conditional on network positioning, students who see themselves as less popular and less central–and those with more accurate self-perceptions–tend to achieve higher grades, whereas individuals recognized by others as popular and central perform significantly better academically. These findings challenge theoretical models that assume accurate self-awareness of network positions and highlight the need to reconsider the implications for key-player interventions in public health, education, and organizational contexts.

In a series of laboratory and online experiments, we investigate the perceived and actual influence, direct and indirect, that early movers have over later movers in a sequential-move binary-action coordination game played on a network. Each human subject is assigned to a particular node in a specified 5 or 10 node network, and chooses In or Out knowing how many neighbors have previously chosen In. We measure influence in terms of the number of In choices that follow an initial exogenous In versus Out choice. Influence is quite heterogeneous across different network positions. Human subjects are aware of their influence and act on it, but overestimate their influence on average. A simple adaptive learning model explains entry and perceptions of influence reasonably well, especially for well connected nodes.

Although mobile banking is seen as a solution to limited access to banking and financial services in the developing world, its adoption rates -especially among women - fall well below expectations. Hence, how can we promote its adoption among the socially and economically disadvantaged? We compare the effectiveness of two strategies, seeded diffusion via incentivised local leaders and a traditional marketing campaign, to promote the adoption of mobile banking among poor women in rural Peru. For the first one, we exploit the existence of local leaders who were trained by a local firm to promote the diffusion of a mobile banking application. For the second, we take advantage of an ongoing regional marketing campaign. Our findings show that the personalized seeded diffusion via local leaders is an effective promotion strategy. It significantly outperforms the traditional campaign, during which adoption rates are statistically indistinguishable from zero and similar to those in our control areas. We additionally show that the seeded incentivised diffusion relies on features of the underlying community networks known to promote trust. Our results emphasize the necessity of personalized approaches to promote technological products such a mobile banking among vulnerable populations.

We introduce a simple behavioral model, counting pros and cons, for decisions under ambiguity. The model predicts that, as the likelihood of winning decreases in two-jar environments proposed in Ellsberg (2011), people should shift from behaving as ambiguity averse to ambiguity seeking. We test this prediction experimentally and find a significant systematic shift as predicted. When the likelihood of winning decreases from 1/2, as in Ellsberg’s (1961), to 1/3, already 50% of subjects choose to bet on the ambiguous jar. This percentage grows with lower underlying probabilities.We also test our model in a less synthetic and more realistic environment. This research contributes to the explanations of behavior under ambiguity via complexity and bounded rationality, rather than preferences to ambiguity, and proposes a novel practical application of the counting-pros-and-cons heuristics.

We report data from an online experiment which allows us to study how generosity changed over a 6-day period during the initial explosive growth of the COVID-19 pandemic in Andalusia, Spain, while the country was under a strict lockdown. Participants (n= 969) could donate a fraction of a €100 prize to an unknown charity. Our data are particularly rich in the age distribution and we complement them with daily public information about COVID-19-related deaths, infections and hospital admissions. We find correlational evidence that donations decreased in the period under study, particularly among older individuals. Our analysis of the mechanisms behind the detected decrease in generosity suggests that expectations about others' behaviour, perceived mortality risk and (alarming) information play a key—but independent—role for behavioural adaptation. These results indicate that social behaviour is quickly adjusted in response to the pandemic environment, possibly reflecting some form of selective prosociality.

There is a long-standing unresolved debate in game theory and experimental economics regarding the behavioral equivalence of the direct-response method (hot play) and the strategy method (cold play). Using a unified experimental framework, we compare behavior elicited via both methods in four different Centipede Games that differ in their incentives to take or pass, in the evolution of those incentives over decision nodes, and in the asymmetry of the incentives across the two player roles. Out of the four Centipede Games, we find that both methods yield statistically different behavior in two of them, while in the remaining two we cannot reject the same behavior across the hot and cold methods. Whenever the behavior diverges, hot play consistently makes individuals stop earlier. These findings should shift the question from whether both methods are generically behaviorally equivalent to under which conditions they are (not) and why.

Prenatal exposure to sex hormones exerts organizational effects on the brain which have observable behavioural correlates in adult life. There are reasons to expect that social behaviours—fundamental for the evolutionary success of humans—might be related to biological factors such as prenatal sex hormone exposure. Nevertheless, the existing literature is inconclusive as to whether and how prenatal exposure to testosterone and oestrogen, proxied by the second-to-fourth digit ratio (2D : 4D), may predict non-selfish behaviour. Here, we investigate this question using economic experiments with real monetary stakes and analyse five different dimensions of social behaviour in a comparatively large sample of Caucasian participants (n = 560). For both males and females, our results show no robust association between right- or left-hand 2D : 4D and generosity, bargaining or trust-related behaviours. Moreover, no differences in behaviour were found according to sex. We conclude that there is no direct correlation between 2D : 4D and these social behaviours.