Since the 1950s, the United Nations (UN) has designated days (e.g., World Wetland Day), years (e.g., Year of the Gorilla) and decades (e.g., Decade on Biodiversity) with a commonly stated goal to raise awareness and funding for conservation-oriented initiatives, and these Days, Years and Decades of ‘…’ (hereafter ‘DYDOs’) continue. However, the effectiveness of these initiatives to achieve their stated objectives and to contribute to positive conservation outcomes is unclear. Here we used a binary analysis change model to evaluate the effectiveness of UN conservation-oriented DYDOs observed between 1974 and 2020. We also examined four case studies to understand the different strategies employed to meet specified conservation goals. We found that DYDOs apparently contributed to positive conservation outcomes when they were tied to social media campaigns and/or when they were strategically situated in current events or global discourse. Although the outcomes of DYDOs were varied, those with longer timescales and those that engaged local communities were more likely to be successful. We suggest that DYDO organizers should identify all possible paths of action through the lens of the change model outlined in this paper to strengthen the value and effectiveness of these initiatives in the future. Using this approach could help ensure that resources are used efficiently and effectively, and that initiatives yield positive conservation outcomes that benefit people and nature.

The highly popular belief that rent-control leads to an increase in the amount of affordable housing is in contradiction with ample empirical evidence and congruent theoretical explanations. It can therefore be qualified as a misconception. We present the results of a preregistered on-line experiment in which we study how to dispel this misconception using a refutational approach in two different formats, a video and a text. We find that the refutational video has a significantly higher positive impact on revising the misconception than a refutational text. This effect is driven by individuals who initially agreed with it and depart from it after the treatment. The refutational text, in turn, does not have a significant impact relative to a non-refutational text. Higher cognitive reflective ability is positively associated with revising beliefs in all interventions. Our research shows that visual communication effectively reduces the gap between scientific economic knowledge and the views of citizens.

We report evidence from an experiment where an employer selects one of two workers to perform a task for a fixed compensation. Workers differ in their ability. The employer’s payoff depends on the worker’s ability and on a non-contractible effort that the worker exerts once employed. We find that selected workers exert an effort higher than the minimum enforceable one. When the employers can send a free-text form message to the selected worker, workers with low ability exert significantly higher effort than the workers with high ability. The difference in effort overcompensates the difference in ability.

This study investigates the mechanisms driving the effectiveness of free-form communication in promoting cooperation within a sequential social dilemma game. We hypothesize that the self-constructing nature of free-form communication enhances the sincerity of messages and increases the disutility of dishonoring promises. Our experimental results demonstrate that free-form messages outperform both restricted promises and treatments where subjects select and use previously constructed free-form messages. Interestingly, we find that selected free-form messages and restricted promises achieve similar levels of cooperation. We observe that free-form messages with higher sincerity increase the likelihood of high-price and high-quality choices, thereby promoting cooperation. These messages frequently include promises and honesty, while threats do not promote cooperation. Our findings emphasize the crucial role of the self-constructed nature of free-form messages in promoting cooperation, exceeding the impact of message content compared to restricted communication protocols.

Within-group communication in competitive coordination games has been shown to increase competition between groups and lower efficiency. This study further explores potentially harmful effects of communication, by addressing the questions of (1) asymmetric communication and (2) the endogenous emergence of communication. Our theoretical analysis provides testable hypotheses regarding the effect of communication on competitive behavior and efficiency. We test these predictions using a laboratory experiment. The experiment shows that although asymmetric communication is not as harmful as symmetric communication, it leads to more aggressive competition and lower efficiency relative to the case when neither group can communicate. Moreover, groups vote to endogenously establish communication channels even though they would earn higher payoffs if jointly they chose to restrict within-group communication.

We conducted a laboratory experiment to study the effects of communication in a dictator game, while maintaining subjects’ anonymity. In the experiment, the recipient has an opportunity to state a payoff-irrelevant request for his/her share before the dictator dictates his/her offer. We found that the independence hypothesis that voice does not matter is rejected. In particular, if the request is for less than half of the pie, the dictator's offer increases as the recipient's request increases. Additionally, there is no dictator who is other-regarding and, at the same time, does not react to the recipient's request.

The present study explores the value of machine learning techniques in the classification of communication content in experiments. Previously human-coded datasets are used to both train and test algorithm-generated models that relate word counts to categories. For various games, the computer models of the classification are able to match out-of-sample the human classification to a considerable extent. The analysis raises hope that the substantial effort going into such studies can be reduced by using computer algorithms for classification. This would enable a quick and replicable analysis of large-scale datasets at reasonable costs and widen the applicability of such approaches. The paper gives an easily accessible technical introduction into the computational method.

We set out to test whether the effect of promises on trustworthiness derives from the fact that they are made (internal consistency) or that they are received (social obligation). The results of an experimental trust game appeared at first to support the former mechanism. Even when trustee messages are not delivered to trustors, trustees who make a promise are more likely to act trustworthy than those who do not make a promise. However, we subsequently ran a control treatment with restricted (non-promise) communication to examine whether the correlation between promises and trustworthiness is causal. The results show that the absence of promises does not decrease average cooperation rates. This indicates that promises do not induce trustworthiness, they are just more likely to be sent by cooperators than by non-cooperators.

This paper studies the vulnerability of the pivotal mechanism with respect to manipulation by groups. In a lab experiment, groups decide on the implementation of various alternatives, some of which imply opposite interests for the two subgroups. We investigate the occurrence of tacit and explicit collusion by allowing for communication within subgroups in one treatment and prohibiting it in another. Even though all agents’ preferences are common knowledge and there exists a simple symmetric collusive strategy for one subgroup, we find little evidence for tacit collusion. Only when explicit communication is allowed, collusion is established. A behavioral model using quantal response equilibrium in which subjects have beliefs over the correlation of errors of same-type subjects helps explain the main features of our data.

We report on an experiment using video technology to study effects of communication on donations to and discrimination between potential receivers. The experimental design eliminates strategic factors by allowing two receivers to unilaterally communicate with an anonymous dictator before the latter decides on her gifts. Through the use of three communication setups (none, audio, and audio-visual) we analyze purely social effects of communication. A silent video channel leads to discrimination between potential receivers based on impression formation, but does not affect average levels of donations. When the auditory channel is added, average donations increase. The social processes invoked by the visual and audio channels are heterogeneous and communicator-specific but not unsystematic.

We augment a standard bilateral gift exchange game so employees can send messages at the same time as choosing an effort level. Employee effort (controlling for wages) is unaffected by allowing messages, but wages dramatically increase. Messages affect wages because employees give managers advice to set higher wages, usually explaining that this will result in higher effort. This advice prompts managers to try higher wages, helping them learn that raising wages increases their payoffs. In a follow-up experiment, we directly provide managers with additional information about the relationship between wages and effort. This too causes wages to increase, but to a lesser extent than allowing messages. Our results highlight the critical role of learning in generating gains from positive gift exchange.

We experimentally investigate the effect of pre-bargaining communication on productive incentives in a multilateral bargaining game with joint production under two conditions: observable and unobservable investments. In both conditions, communication fosters fair sharing and is rarely used to pit individuals against each other. Proportional sharing arises with observable investments with or without communication, leading to high efficiency gains. Without investment observability, communication is widely used to truthfully report investments and call for equitable sharing, allowing substantial efficiency gains. Since communication occurs after production, our results highlight a novel indirect channel through which communication can enhance efficiency in social dilemmas. Our results contrast with previous findings on bargaining over an exogenous fund, where communication leads to highly unequal outcomes, competitive messages, and virtually no appeals to fairness.

We experimentally study optional costly communication in Stag-Hunt games. Prior research demonstrates that efficient coordination is difficult without a communication option but obtains regularly with mandatory costless pre-play messages. We find that even small communication costs dramatically reduce message use when communication is optional, but efficient coordination can occur with similar frequency as under costless communication. These findings can be accounted for by formalizations of forward induction that take Nash equilibrium as a reference point (such as Kohlberg and Mertens in Econometrica 54: 1003–1037, 1986; Govindan and Wilson in Econometrica 77: 1–28, 2009), while formalizations that only appeal to (higher-order) knowledge of rationality remain silent in this environment.

We conduct experiments comparing the performance of individuals and teams of four subjects in solving two rather different tasks. The first involves nonograms, logic puzzles that require a series of incremental steps to solve. The second task uses CRT-type questions, which require a single, specific insight. Contrary to the existing literature, team performance in both tasks is statistically indistinguishable from that of individuals when communication is costless. If a tiny message cost is imposed, team performance improves and becomes statistically better than that of individuals, although still worse than previous research on teams would have suggested. To the best of our knowledge, our study is the first to find that imposing friction on communication leads to more effective performance in teams. Message costs reduce the quantity of messages but increase the quality, specifically the mix of good and bad suggestions. The improved quality of communication with message costs allows teams to out-perform individuals. Our analysis suggests that organizations would do better by identifying an able individual to perform an intellective task rather than using teams; prediction exercises indicate that this will not harm, and will generally increase, performance relative to a team, and only requires the cost of paying one individual rather than many.

It is still an open question when groups perform better than individuals in intellective tasks. We report that in an Acquiring a Company game, what prevailed when there was disagreement among group members was the median proposal and not the best proposal. This aggregation rule explains why groups underperformed with respect to a “truth wins” benchmark and why they performed better than individuals deciding in isolation in a simple version of the task but worse in the more difficult version. Implications are drawn on when to employ groups rather than individuals in decision making.

We examine repetition as an institution that affects coordination failure in a game with and without pre-play communication. We use probit regression with random effects to test hypotheses regarding the frequency and form of coordination failure in the presence of repeated play versus one-shot games. Our results indicate that repetition without pre-play communication results in a lower frequency of coordination failure relative to one-shot game outcomes. This result is reversed when pre-play communication is allowed. Our evidence also suggests that repeated play coordination failures tend to be suboptimal Nash equilibria, whereas one-shot game coordination failures are disequilibria regardless of the presence of pre-play communication.

This study experimentally examines the role of indirect higher order beliefs in sequential psychological games. We consider a three-player sequential game in which the first and third players do not interact sequentially, but only through an intermediary, the second player. We posit that the third player’s decision to cooperate depends on his indirect higher order belief, namely, his belief about what the first player believes the second player would choose. We employ pre-play communication between the first and third players as a way to influence the third player’s indirect higher order belief. The evidence demonstrates that communication can effectively induce cooperation from the third player by shaping his indirect higher order belief.

We investigate contract negotiations in the presence of externalities and asymmetric information in a controlled laboratory experiment. In our setup, it is commonly known that it is always ex post efficient for player A to implement a project that has a positive external effect on player B. However, player A has private information about whether or not it is in player A’s self-interest to implement the project even when no agreement with player B is reached. Theoretically, an ex post efficient agreement can always be reached if the externality is large, whereas this is not the case if the externality is small. We vary the size of the externality and the bargaining process. The experimental results are broadly in line with the theoretical predictions. However, even when the externality is large, the players fail to achieve ex post efficiency in a substantial fraction of the observations. This finding holds in ultimatum-game bargaining as well as in unstructured bargaining with free-form communication.