Our study contributes to the literature on choice shifts in group decision-making by analyzing how the level of risk-taking within a group is influenced by its gender composition. In particular, we investigate experimentally whether group composition affects how preferences ‘shift’ when comparing individual and group choices. Consistent with hypotheses derived from previous literature, we show that male-dominated groups shift toward riskier decisions in a way that is not explained by any simple preference aggregation mechanism. We discuss potential channels for the observed pattern of choice shifts.

Efficient coordination is a major source of efficiency gains. We study in an experimental coordination game with 727 children and teenagers, aged 9 to 18 years, the strategies played in pre-adulthood. In our one-shot, experimental coordination game, we vary the incentives for reaching the more efficient equilibrium and the number of subjects within a group. Looking at strategy choices dependent on age, we do not find robust age effects in the aggregate. Yet, we see that smaller group sizes and larger incentives increase the likelihood of choosing the efficient strategy. The larger strategic uncertainty in larger groups is obviously harmful for overall efficiency. Regarding incentives, we find that increasing the profits in the efficient equilibrium seems to work better than providing a cushion in case of miscoordination. Beliefs play an important role as well, as subjects are more likely to play the efficient strategy when they expect others to do so as well. Our results are robust to controlling for individual risk-, time-, and social preferences.

Individuals often need to self-promote for social and professional recognition. In this paper, we investigate the existence of a gender gap in self-promotion of a prosocial action and explore its link with modesty norms. Using a novel experiment that combines both lab and field elements, we show that women are up to five times less likely to self-promote than men. We find suggestive evidence that the difference in behaviour across gender is determined by women’s social image concerns of being perceived as immodest. We find that the provision of a justification to self-promote has two important consequences: (i) it leads to an increase in self-promotion by women and (ii) contributes to the elimination of the gender gap in self-promotion behaviour.

This introduction presents the two-part Special Issue of honoring the life and work of Amnon Rapoport (1936–2022), a pioneering scholar whose six decades of research shaped experimental studies of interactive decision making. Rapoport’s hallmark was the interplay between formal game-theoretic modeling and rigorous laboratory testing, advancing understanding in coalition formation, social dilemmas, market entry, traffic networks, decision timing, resource dilemmas, behavioral operations, and methodological innovation. The 27 articles collected across the volumes revisit and extend these themes, offering fresh insights into how rationality assumptions succeed and fail in predicting human behavior. Together, the contributions reflect both continuity with Rapoport’s intellectual credo—“model first, test second, refine third”—and renewal through new methods and applications. Beyond scholarship, the issue pays tribute to Rapoport’s extraordinary role as a mentor and his enduring influence on the evolution of behavioral and experimental economics

In various organizational settings, a team member is given the authority to make an investment decision that influences the value of the jointly produced surplus. We experimentally investigate the effect of asymmetric status, investment decisions, and the outcome of these decisions on bargaining behavior and outcomes. Agents’ initial contributions to the surplus are determined by their relative performances in a real-effort task. Three treatments vary in how the final surplus value is determined. We observe that when low-contributors take a risk, they are punished (rewarded) for failure (success), whereas high-contributors receive a fixed share independent of the outcome. Analysis of bargaining process variables, subjects’ communication during bargaining, and third parties’ normative judgments provides further insights into the possible mechanism behind this observation.

In recent years, there has been an increasing interest in motivated memory as a psychological determinant of economic outcomes. According to motivated memory, people tend to better recall pleasant information because it serves their psychological needs. Another phenomenon, however, predicts the same pattern: According to mood congruence, pleasant information is easier to recall for individuals in nonnegative mood, regardless of any psychological needs. Since most people tend to have some need for self-esteem and to experience more positive than negative feelings during the day, the two phenomena predict similar outcomes in most ordinary situations, but not all. To test the predictive power of these two phenomena, we collect data from a laboratory experiment and from a nationally representative survey. We study how individuals in a temporarily induced negative mood (via a video clip) or those who report a low baseline mood (relative to the population) recall negative feedback. Our results meet the predictions of motivated memory: Individuals better recall positive than negative feedback, even when they are in negative mood. Motivated memory is not just a matter of mood.

In the presence of a default option, the optimal search rule for an agent with a reference-dependent utility and a search cost predicts: (i) the default increases the reservation utility due to the reference effect, leading to a better choice, and (ii) those with higher reservation utility will self-select into search and are more likely to find a superior option. Our experiments document the presence of both effects. Those who reject the default are likely to find higher-ranked options in their active search, supporting the self-selection effect. Even when the self-selection channel is shut down, the reference effect remains.

Agents frequently engage with multiple principals simultaneously – for example, when borrowing from several banks or peers. In such settings, principals typically possess less information about the agent’s ability or intentions (e.g., to repay a loan) and must rely on trust. This paper presents experimental evidence from trust games framed in a credit market context to examine the role of reciprocity in interactions involving multiple principals (lenders) and a single agent (borrower). Agents were asked to decide whether to act trustworthily and repay, or to default and act selfishly, after receiving the same credit amount from either one or multiple principals. The results show that reciprocity declines when the number of trusting principals increases. A key mechanism appears to be the reduced marginal harm that an agent’s default imposes on each individual principal. Additionally, agents seem less sensitive to the negative consequences of their actions when multiple principals are affected. These findings suggest that interactions involving multiple principals are behaviorally riskier than bilateral ones. The results have implications for the design of incentive structures in multi-principal-agent environments, such as crowdlending platforms.

Social interactions frequently take place under the shadow of the future. Previous literature explains cooperation in indefinitely repeated prisoner’s dilemma as driven predominantly by self-interested strategic considerations. This paper provides a causal test of the importance of social preferences in such contexts. In a series of pre-registered experiments, we show that high levels of cooperation can be sustained when prosocial individuals interact in segregated groups. By comparing their behavior with that of mixed and selfish groups, we highlight the conditions under which other-regarding motivations matter in repeated interactions.

While market design advocates for the importance of good design to achieve desirable properties, experiments on coalition formation theory have shown fragility in proposed mechanisms to do so. We experimentally investigate the effectiveness of “structured” mechanisms that implement the Shapley value as an ex ante equilibrium outcome with those of corresponding “semi-structured” bargaining procedures. We find a significantly higher frequency of grand coalition formation and higher efficiency in the semi-structured than in the structured procedures regardless of whether they are demand-based or offer-based. While significant differences in the resulting allocations are observed between the two structured procedures, little difference is observed between the two semi-structured procedures. Finally, the possibility of free-form chat induces an equal division more frequently than occurs without it. Our results suggest that when it comes to bargaining and coalition formation, not having various restrictions imposed by different mechanisms may lead to more desirable outcomes.

In two sets of novel laboratory experiments, we show that the mere presence of an existing alliance at the onset of coalition formation may lead managers to form economically suboptimal alliances. Study Set 1 considers alliance formation when a focal firm is already embedded in an existing coalition. These studies show evidence of a status quo bias: participants managing the focal firm tend to include the current partner in alliance offers and thus are less successful in forming optimal alliances compared to those in an unattached control condition. Study Set 2 examines the extent to which an unattached focal firm attempts to ‘poach’ away attractive coalition partners from their embedded alliances. Our results show evidence of poaching avoidance: participants make fewer offers to, and are less likely to partner with, an attractive firm already in an alliance. However, this tendency to avoid poaching may be attenuated when the existing coalition is perceived as a powerful threat and/or alternate partners are unavailable. These findings provide behavioral insights into how judgmental biases can constrain alliance formation. We conclude with a discussion of how selected environmental, firm, and decision-maker characteristics (e.g., turbulence, embedded relationships, and risk orientation) may moderate these results.

Large Language Models (LLMs) have the potential to profoundly transform and enrich experimental economic research. We propose a new software framework, “alter_ego”, which makes it easy to design experiments between LLMs and to integrate LLMs into oTree-based experiments with human subjects. Our toolkit is freely available at github.com/mrpg/ego. To illustrate, we run differently framed prisoner’s dilemmas with interacting machines as well as with human-machine interaction. Framing effects in machine-only treatments are strong and similar to those expected from previous human-only experiments, yet less pronounced and qualitatively different if machines interact with human participants.

We report a lab experiment to study subjects’ preferences over their ordinal rank in an earnings distribution. Following an assignment of unequal earnings, subjects can select a monetary transfer from exactly one individual to another, not including themselves. This can potentially change their own position in the distribution, as well as influence overall inequality. The experiment varies whether the initial earnings assignment is random or is affected by preliminary competition. It also varies the reference group from a complete to a partial network. A majority of observed transfers reduce inequality by moving earnings from those with the highest rank to the lowest rank in the distribution. Rank-improving transfers are substantially more common for preliminary competition losers than winners. Transfers to individuals outside of the reference group are not uncommon, and they usually target as the source the individuals high in the income distribution. While generally weak overall, own rank preferences appear to be more common among men than women.

We present a simple and robustly incentive-compatible price list methodology to elicit quantiles of a subjective real-valued belief. These elicited quantiles can be employed to approximate a subject’s complete subjective distribution, and we establish that the distribution maximizing entropy while adhering to the elicited quantiles is piecewise linear. Using this approach, our methodology extends to estimating arbitrary unobserved attributes of the subjective distribution, such as mean and variance, which are otherwise challenging to elicit. We provide a proof-of-concept for our framework through an experiment involving the elicitation of participants’ beliefs regarding the mathematical abilities of their peers.

We report two meta-analyses on the determinants of antisocial behavior in experimental settings in which such behavior is not rationally motivated by pecuniary incentives. The first meta-analysis employs aggregate data from 95 published and unpublished studies (24,086 participants), using laboratory, field and online experiments carried out since 2000. We find that antisocial behavior depends significantly on the experimental setting, being highest in vendetta games and lowest in social dilemmas. As we find significant heterogeneity across the studies, including across game classes, in the second meta-analysis, we focus only on “Joy of Destruction” (JoD) and money-burning (MB) experiments, for which we have the most observations, 51 studies and around 16,784 participants. Overall, our findings suggest that procedural fairness and being observed by others reduce the frequency of antisocial behavior. Online and field experiments display more antisocial behavior than laboratory experiments. We also find that the strategy method biases antisocial behavior upward. However, we do not find evidence for a positive publication bias being correlated with higher destructive behavior, either in the general meta-analysis or in relation to JoD/MB experiments; if anything, there is evidence of a negative publication bias. The JoD/MB meta-analysis finds evidence of a price effect for destruction frequency, negative discrimination against outsiders, within-subject designs underestimating destructive behavior, and more antisocial behavior in one-shot interactions. Collectively, our results point to the value of more laboratory experiments that systematically build on paradigmatic experimental designs to enable comparability and the identification of key economic drivers of antisocial behavior.

Explicit and implicit incentives and opportunities for mutually beneficial voluntary cooperation coexist in many economic relationships. In a series of eight laboratory gift-exchange experiments, we show that incentives can lead to crowding out of voluntary cooperation even after they have been abolished. This crowding-out also occurs in repeated relationships, which otherwise strongly increase effort compared to one-shot interactions. Using a unified econometric framework, we unpack these results as a function of positive and negative reciprocity, as well as the principals’ wage offer and the incentive compatibility of the contract. Crowding-out occurs mostly due to reduced wages and not a change in reciprocal wage–effort relationships. Our systematic analysis also replicates established results on gift exchange, incentives, and crowding out of voluntary cooperation while being exposed to incentives. Overall, our findings show that the behavioral consequences of explicit incentives strongly depend on the features of the situation in which they are embedded.

A zero price effect is a discontinuous change in demand when price is reduced to zero from a level arbitrarily close to it. It has been proposed that social norms play a role in zero price effects on consumption. We first conducted a norm-elicitation experiment to measure how people perceive the social appropriateness of consumption under zero versus minimal prices. We then ran a natural field experiment in the same contexts to observe actual taking behavior. Results show that the social appropriateness of consuming high quantities is significantly lower when goods are offered for free than when they are sold at 1 cent. Zero pricing increases the proportion of individuals who consume something, but reduces the average amount taken by those who consume positive amounts. Overall, the evidence suggests that high consumption of free goods is prevented by its social inappropriateness, potentially helping to explain the inconsistent evidence on the direction of zero price effects in previous studies.

How do bribes and lobbying distort judgment? In our experiment, referees are tasked with judging a worker’s performance, and awarding a bonus to workers who score above a certain threshold. We find that bribes and lobbying are both distortionary, but in different ways. Whereas lobbying increases the number of workers receiving a bonus, bribes weaken the relationship between performance and success, with bonuses mostly being awarded to workers who bribe. We discuss implications for anti-corruption interventions.

While almost all charities rely on a set of donor appreciation strategies, their effectiveness for the success of fundraising campaigns is underresearched. Through two preregistered field studies conducted in collaboration with a leading German opera house (N = 10,000), we explore the significance of expressing gratitude and examine two different approaches to doing so. Our first study investigates the impact of a ‘thank you in advance’ statement in fundraising letters, a common strategy among fundraisers. In the second study, we explore the effectiveness of handwritten thankyou postcards versus printed postcards, shedding light on the roles of personalization and handwriting in donor appeals. Our findings challenge conventional wisdom, revealing that neither ‘thank you in advance’ nor handwritten thank you notes significantly affect donor contributions.

We conduct an economic experiment to examine the causal impact of social ties on the preference for competition. Participants decide whether to engage in a competition or not. Across four treatments, potential competitors vary based on their relationship with the decision-maker: whether they had a conversation with the decision-maker prior to the competition, whether they are expected to chat after the competition, or both, or neither. We find that the process of chatting increases social closeness. This increase in social closeness tends to reduce the preference for competition when participants are expected to meet again after the competition. However, it does not change the likelihood of opting for competition if there is no prospect of further interaction. Through this experiment, we thus uncover previously unknown implications of managerial practices, such as team-building exercises and remote work options, that influence the formation of social ties.