Competition for Resources

La abeja melífera (Apis mellifera L.) es una especie que, por su utilidad, se ha expandido gracias al Hombre por todo el globo, siendo la principal especie de abeja invasora. A pesar de ser considerada una especie benéfica, existe controversia en torno a los impactos que puede provocar su alta densidad en hábitats naturales. Aquí revisamos los principales efectos y mecanismos atribuidos a un incremento en la abundancia de la abeja melífera sobre plantas y abejas silvestres. Encontramos que los impactos pueden ser positivos y negativos, jugando un papel importante el contexto ecológico (disponibilidad de recursos, comunidad de polinizadores silvestres) como también la densidad de la abeja melífera. Los efectos ocurren a escala de individuo, población y comunidad afectando las redes planta-polinizador mientras que las consecuencias para el funcionamiento de los ecosistemas son inciertas. Recientemente se ha demostrado que la abeja melífera puede actuar como agente de selección afectando la evolución de plantas en un lapso relativamente breve de tiempo. La transmisión de parásitos y patógenos de la abeja melífera a otras especies de abejas ha ganado relevancia en este último tiempo. Si bien la abeja melífera puede beneficiar la polinización de plantas silvestres, al ser los impactos en abejas casi puramente negativos es necesario ser cautelosos con la introducción de colmenas en áreas naturales; particularmente hasta no determinar las consecuencias de la transmisión de parásitos y patógenos.

We propose an intergroup competition scheme (ICS) to solve the free-riding problem in the public goods game. Our solution only requires knowledge of the group contributions, is budget balanced and with the right parameters a dominant strategy. The main innovations of our design are that the prize to the winning group is paid by the losing group and that the size of the transfer depends on the difference in contribution by the two groups. With the right parameters, this scheme changes the dominant strategy from none to full contribution. We tested different parameterizations for the ICS. The experiments show dramatic gains in efficiency in all the ICS treatments. Moreover, versions of the ICS in which intergroup competition should not change the zero contribution Nash equilibrium also produce remarkable gains in efficiency and no decline in contributions over time.

1. Despite their low contribution to forest carbon stocks, lianas (woody vines) play an important role in the carbon dynamics of tropical forests. As structural parasites, they hinder tree survival, growth and fecundity; hence, they negatively impact net ecosystem productivity and long-term carbon sequestration. 2. Competition (for water and light) drives various forest processes and depends on the local abundance of resources over time. However, evaluating the relative role of resource availability on the interactions between lianas and trees from empirical observations is particularly challenging. Previous approaches have used labour-intensive and ecosystem-scale manipulation experiments, which are infeasible in most situations. 3. We propose to circumvent this challenge by evaluating the uncertainty of water and light capture processes of a process-based vegetation model (ED2) including the liana growth form. We further developed the liana plant functional type in ED2 to mechanistically simulate water uptake and transport from roots to leaves, and start the model from prescribed initial conditions. We then used the PEcAn bioinformatics platform to constrain liana parameters and run uncertainty analyses. 4. Baseline runs successfully reproduced ecosystem gas exchange fluxes (gross primary productivity and latent heat) and forest structural features (leaf area index, aboveground biomass) in two sites (Barro Colorado Island, Panama and Paracou, French Guiana) characterized by different rainfall regimes and levels of liana abundance. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Artículo publicado en Open Access bajo los términos de Creative Commons attribution Non Comercial License 3.0. MONOGRÁFICO: Pérdida de polinizadores: evidencias, causas y consecuencias ecosistemas REVISTA CIENTÍFICA DE ECOLOGÍA Y MEDIO AMBIENTE

Your article is protected by copyright and all rights are held exclusively by International Union for the Study of Social Insects (IUSSI). This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".

In food markets the use of labels with collective reputations is widespread. Examples are organic or fair trade labels. These labels signal credence attributes of products which cannot be verified by consumers. Producers may mis-label their products to collect the premium associated to such collective reputations. We examine the propensity for fraud to emerge in a multi-player, collective action game. An important feature of our framework is that the premium depends on the proportion of mis-labeling in the market. We experimentally test the impact of market size, alternative monitoring and subsidy on the propensity to mis-label. In line with our theoretical predictions we find that more stringent monitoring and enforcement schemes and the presence of a subsidy reduce the propensity to mislabel, while an increase in market size elevates it.

Your article is protected by copyright and all rights are held exclusively by International Union for the Study of Social Insects (IUSSI). This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".

Your article is protected by copyright and all rights are held exclusively by International Union for the Study of Social Insects (IUSSI). This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".

In food markets the use of labels with collective reputations is widespread. Examples are organic or fair trade labels. These labels signal credence attributes of products which cannot be verified by consumers. Producers may mis-label their products to collect the premium associated to such collective reputations. We examine the propensity for fraud to emerge in a multi-player, collective action game. An important feature of our framework is that the premium depends on the proportion of mis-labeling in the market. We experimentally test the impact of market size, alternative monitoring and subsidy on the propensity to mis-label. In line with our theoretical predictions we find that more stringent monitoring and enforcement schemes and the presence of a subsidy reduce the propensity to mislabel, while an increase in market size elevates it.

According to theory a pure meritocracy is efficient because individual members are competitively rewarded according to their individual contributions to society. However, purely individually based meritocracies seldom occur. We introduce a new model of social production called ���team-based meritocracy���(TBM) in which individual members are rewarded based on their team membership. We demonstrate that as long as such team membership is both mobile and competitively based on contributions, individuals are able ...

Access to water, in sufficient quantities and of sufficient quality is vital for human health. The United Nations Committee on Economic, Social and Cultural Rights (in General Comment 15, drafted 2002) argued that access to water was a condition for the enjoyment of the right to an adequate standard of living, inextricably related to the right to the highest attainable standard of health, and thus a human right. On 28 July 2010 the United Nations General Assembly declared safe and clean drinking water and sanitation a human right essential to the full enjoyment of life and all other human rights. This paper charts the international legal development of the right to water and its relevance to discussions surrounding the growth of unconventional energy and its heavy reliance on water. We consider key data from the country with arguably the most mature and extensive industry, the USA, and highlight the implications for water usage and water rights. We conclude that, given the weight of...

Your article is protected by copyright and all rights are held exclusively by International Union for the Study of Social Insects (IUSSI). This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".

Access to water, in sufficient quantities and of sufficient quality is vital for human health. The United Nations Committee on Economic, Social and Cultural Rights (in General Comment 15, drafted 2002) argued that access to water was a condition for the enjoyment of the right to an adequate standard of living, inextricably related to the right to the highest attainable standard of health, and thus a human right. On 28 July 2010 the United Nations General Assembly declared safe and clean drinking water and sanitation a human right essential to the full enjoyment of life and all other human rights. This paper charts the international legal development of the right to water and its relevance to discussions surrounding the growth of unconventional energy and its heavy reliance on water. We consider key data from the country with arguably the most mature and extensive industry, the USA, and highlight the implications for water usage and water rights. We conclude that, given the weight of...

Most savanna water balance models assume water partitioning between grasses and shrubs in a twolayer hypothesis, but this hypothesis has not been tested for humid savanna environments. Spatial partitioning of soil water between grasses and shrubs was investigated in a West African humid savanna by comparing the isotopic composition (oxygen-18 and deuterium) of soil water and plant stem water during rainy and dry conditions. Both grass and shrub species acquire most of their water from the top soil layer during both rainy and dry periods. A shift of water uptake pattern towards deeper horizons was observed only at the end of the dry season after shrub defoliation. The mean depth of water uptake, as determined by the isotopic signature of stem water, was consistent with grass and shrub root profiles and with changes in soil water content profiles as surveyed by a neutron probe. This provides evidence for potentially strong competition between shrubs and grasses for soil water in these humid savannas. Limited nutrient availability may explain these competitive interactions. These results enhance our understanding of shrub-grass interactions, and will contribute to models of ecosystem functioning in humid savannas.

This paper investigates fund-raising mechanisms based on a prize as a way to overcome free riding in the private provision of public goods, under the assumptions of income heterogeneity and incomplete information about income levels. We compare experimentally the performance of a lottery, an all-pay auction and a benchmark voluntary contribution mechanism. We find that prize-based mechanisms perform better than voluntary contribution in terms of public good provision after accounting for the cost of the prize. Comparing the prize-based mechanisms, total contributions are significantly higher in the lottery than in the all-pay auction. Focusing on individual income types, the lottery outperforms voluntary contributions and the all-pay auction throughout the income distribution.

This paper investigates fund-raising mechanisms based on a prize as a way to overcome free-riding in the private provision of public goods, under the assumptions of income heterogeneity and incomplete information regarding income levels. We compare experimentally the performance of a lottery, an all-pay auction and a benchmark voluntary contribution mechanism. We find that prize-based mechanisms dominate voluntary contribution in terms of overall public good provision, after accounting for the cost of the prize. Comparing the two prize-based mechanisms, contributions are significantly larger in the lottery than in the all-pay auction. Focusing on individual income types, the lottery dominates the all-pay auction throughout the income distribution. * We thank Roberto Reale for his contribution to this paper, and participants at the ESA 2006 meeting, Nottingham, for their helpful comments. We gratefully acknowledge financial support from Econometica.

This paper investigates single and multiple prize contests as incentive mechanisms for the private provision of public goods, under the assumptions of income heterogeneity and incomplete information about income levels. We compare experimentally a one-prize contest with a three-prize contest in a case where theory predicts that several prizes maximise revenues. We find that, contrary to the theoretical predictions, total contributions are significantly higher in the one-prize contest. In both treatments contributions converge towards theoretical predictions over successive rounds, but the effects of repetition are different: convergence is fast in the one-prize treatment, while gradual and with some undershooting in the three-prize treatment. Focusing on individual income types, the better performance of the single-prize contest is largely explained by the contributions of highincome individuals: a single larger prize provides a more effective incentive for richer individuals than three smaller prizes.

This paper investigates fundraising mechanisms based on prizes as a way to overcome free riding in the private provision of public goods, under the assumptions of income heterogeneity and incomplete information about income levels. We compare experimentally the performance of a lottery, a one-prize contest, a three-prize contest and a benchmark voluntary contribution mechanism. We find that prize-based mechanisms dominate voluntary contribution in terms of public good provision after accounting for the ...

New experimental evidence extending the investigation of free-riding behavior in public goods provision is presented. Procedures are developed to deal with the logistical problems inherent in experiments involving many subjects. Data from Voluntary Contribution Mechanism experiments are reported utilizing group sizes of 4, 10, 40 and 100. These experiments provide replicable results that contradict the widely held view that a group's ability to provide the optimal level of a pure public good is inversely related to group size. On the contrary, groups of size 40 and 100 provided the public good more efficiently than groups of size 4 and 10. Several possible alternative explanations are discussed.

New experimental evidence extending the investigation of free-riding behavior in public goods provision is presented. Procedures are developed to deal with the logistical problems inherent in experiments involving many subjects. Data from Voluntary Contribution Mechanism experiments are reported utilizing group sizes of 4, 10, 40 and 100. These experiments provide replicable results that contradict the widely held view that a group's ability to provide the optimal level of a pure public good is inversely related to group size. On the contrary, groups of size 40 and 100 provided the public good more efficiently than groups of size 4 and 10. Several possible alternative explanations are discussed.

Experiments are reported that add to the growing literature on the voluntary provision of public goods. Information conditions are manipulated to address whether early findings of above-equilibrium contributions to a public good are a result of complete information regarding the symmetry of the game. No significant information effect was found. Further, by examining designs with an interior Nash equilibrium, this research suggests that the nonzero contributions observed in the previous dominant strategy environments, where the prediction was a zero level of provision of the public good, were not simply transitional errors as the system converged to a boundary equilibrium.

Approaching behaviour that produces environmental harm through the medium of criminal sanctions (largely involving monetary penalties) has been criticised consistently as failing to prevent environmental crimes and harms, and failing to concurrently reduce environmental re-offending. Furthermore, important state-corporate political and economic relationships exist that ensure the continuation of environmental degradation. We suggest that a way to overcome this is to rework the current legal system to one grounded in Earth jurisprudence. Although we realise that state-corporate relationships would likely prevent the implementation of Earth jurisprudential principles, we argue such principles are essential to upend the prioritisation of economic imperatives over ecological values within capitalist societies. To demonstrate the strength and utility of the Earth jurisprudential approach, we use the case of fracking for shale gas in the United Kingdom to examine how Earth jurisprudential principles could prevent environmental harm from occurring.

and Keywords In 2010, rare earths were thrust into geopolitical prominence overnight as a result of a territorial incident between Japan and China. China's "unacknowledged" and short-lived rare earths embargo against Japan, coupled with China's decision to sharply reduce export quotas of these materials to all industrial nations, brought home the potential dangers of its near-monopoly position on their production and export. Prices skyrocketed and the international outcry intensified because the seventeen rare-earth elements are critical inputs for high-tech, defense, and renewable energy sources. Given their centrality, the rare-earth crisis is not merely a trade dispute. It raises questions about China's use of economic statecraft and the impacts of growing worldwide resource competition while pointing to the complexities facing policymakers as they develop strategies and responses in an increasingly globalized world.

Access to water, in sufficient quantities and of sufficient quality is vital for human health. The United Nations Committee on Economic, Social and Cultural Rights (in General Comment 15, drafted 2002) argued that access to water was a condition for the enjoyment of the right to an adequate standard of living, inextricably related to the right to the highest attainable standard of health, and thus a human right. On 28 July 2010 the United Nations General Assembly declared safe and clean drinking water and sanitation a human right essential to the full enjoyment of life and all other human rights. This paper charts the international legal development of the right to water and its relevance to discussions surrounding the growth of unconventional energy and its heavy reliance on water. We consider key data from the country with arguably the most mature and extensive industry, the USA, and highlight the implications for water usage and water rights. We conclude that, given the weight of testimony of local people from our research, along with data from scientific literature, non-governmental organization (NGO) and other policy reports, that the right to water for residents living near fracking sites is likely to be severely curtailed. Even so, from the data presented here, we argue that the major issue regarding water use is the shifting of the resource from society to industry and the demonstrable lack of supply-side price signal that would demand that the industry reduce or stabilize its water demand per unit of energy produced. Thus, in the US context alone, there is considerable evidence that the human right to water will be seriously undermined by the growth of the unconventional oil and gas industry, and given its spread around the globe this could soon become a global human rights issue.

Publicly provided goods often create differential payoffs due to timely or spatial distances of group members. We design and test a provision mechanism which utilizes rank competition to mitigate free-riding in impure public goods. In our Rank-Order Voluntary Contribution Mechanism (Rank-Order-VCM) group members compete via observable contributions for a larger share of the public good; high contributors receive preferential access (a larger share), while low contributors receive restricted access (a lower share). In a laboratory experiment Rank-Order-VCM elicits median contributions equal to the full endowment throughout the finitely played games with constant groups. In the control treatment, with randomly assigned ranks, the contributions are significantly lower and decline over time. We thus provide evidence of rank competition, in situations where discriminatory access to public goods is possible, being efficiency enhancing.

We examine theoretically and experimentally how a society's grouping and stratification rules affect incentives and efficiency, and compare meritocratic and ascriptive grouping. We present a multi-level model of social production, and extend the usual single-grouplevel analysis of cooperation to a broadly defined system, in which individuals compete for inclusion in stratified groups based on the contributions they make. Group members share their collective output equally amongst themselves. The mechanism has two pure strategy Nash equilibria, one close to Pareto optimal. The latter equilibrium is asymmetric and rather complex for experimental subjects. Nonetheless, subjects tacitly coordinate this equilibrium very reliably, demonstrating equilibrium's predictive power and providing empirical support for payoff dominance. Our behavioral findings also point to a meritocracy's "naturalness" and effectiveness in eliciting high social contributions. The results make a theoretical and empirical case for why social organization should be based on contribution rather than privilege. They also indicate why societies are increasingly becoming performance-based meritocracies, and are relevant to many forms of contemporary social organization.

A new mechanism that substantially mitigates social dilemmas is examined theoretically and experimentally. It resembles the voluntary contribution mechanism (VCM) except that in each decision round subjects are ranked and then grouped according to their public contribution. The game, particularly in a discrete implementation, has multiple mostly asymmetric, Pareto-ranked pure-strategy equilibria which are rather counterintuitive, yet experimental subjects tacitly coordinate the payoff-dominant equilibrium reliably and quite precisely. In the VCM grouping is random which, with its arbitrary relation to contribution corresponds to any grouping unrelated to output, for example grouping based on race or gender. The new mechanism resembles a meritocracy since based on how much they contribute participants are assigned to strata that vary in payoff. The findings shed light on the nature of merit-based social and organizational grouping and provide guidelines for future research and application.

We examine theoretically and experimentally how a society's grouping and stratification rules affect incentives and efficiency, and compare meritocratic and ascriptive grouping. We present a multi-level model of social production, and extend the usual single-grouplevel analysis of cooperation to a broadly defined system, in which individuals compete for inclusion in stratified groups based on the contributions they make. Group members share their collective output equally amongst themselves. The mechanism has two pure strategy Nash equilibria, one close to Pareto optimal. The latter equilibrium is asymmetric and rather complex for experimental subjects. Nonetheless, subjects tacitly coordinate this equilibrium very reliably, demonstrating equilibrium's predictive power and providing empirical support for payoff dominance. Our behavioral findings also point to a meritocracy's "naturalness" and effectiveness in eliciting high social contributions. The results make a theoretical and empirical case for why social organization should be based on contribution rather than privilege. They also indicate why societies are increasingly becoming performance-based meritocracies, and are relevant to many forms of contemporary social organization.

A new mechanism that substantially mitigates social dilemmas is examined theoretically and experimentally. It resembles the voluntary contribution mechanism (VCM) except that in each decision round subjects are ranked and then grouped according to their public contribution. The game, particularly in a discrete implementation, has multiple mostly asymmetric, Pareto-ranked pure-strategy equilibria which are rather counterintuitive, yet experimental subjects tacitly coordinate the payoff-dominant equilibrium reliably and quite ...

We report an experiment in which the Intergroup Prisoner's Dilemma (IPD) game was contrasted with a structurally identical (single-group) Prisoner's Dilemma (PD). The games were played repeatedly for 40 rounds. We found that subjects were initially more likely to cooperate in the IPD game than in the PD game. However, cooperation rates decreased as the game progressed and, as a result, the differences between the two games disappeared. This pattern is consistent with the hypothesis that subjects learn the structure of the game and adapt their behavior accordingly. Computer simulations based on a simple learning model by Roth and Erev (Learning in extensive-form games: Experimental data and simple dynamic models in the intermediate term, Games and Economic Behavior 8, 164-212, 1995) support this interpretation.

This paper extends the research on incentive compatible institutions for the provision of public goods by imposing a minimum contribution that must be met in order for an individual to enjoy the benefits of the public good. Excluding individuals who do not contribute at least the minimum transforms the linear n-player pure public goods game to an n-player coordination game with multiple, Pareto-ranked Nash equilibria. The experimental results show that exclusion increases contributions to the public good in most cases. However, an increase in contributions may not be sufficient to increase social welfare because there is a welfare cost to excluding individuals when the good is non-rival. Furthermore, exclusion can decrease both contributions and welfare in environments in which individuals fail to coordinate their contributions. The results are sensitive to the minimum contribution requirement and to the relative returns from the public and private alternatives.

In an article published in this journal, Rapoport and Amaldoss [Rapoport, A., Amaldoss, W., 2000. Mixed strategies and iterative elimination of strongly dominated strategies: an experimental investigation of states of knowledge. Journal of Economic Behavior and Organization 42, 483-521] analyze symmetric and asymmetric investment games similar to two-player all-pay auctions with bid caps. In this note, we correct an error in their characterization of the set of Nash equilibria of their symmetric investment game. We discuss the implications for the analysis of data from Rapoport and Amaldoss's experiments.

Most savanna water balance models assume water partitioning between grasses and shrubs in a two-layer hypothesis, but this hypothesis has not been tested for humid savanna environments. Spatial partitioning of soil water between grasses and shrubs was investigated in a West African humid savanna by comparing the isotopic composition (oxygen-18 and deuterium) of soil water and plant stem water during rainy and dry conditions. Both grass and shrub species acquire most of their water from the top soil layer during both rainy and dry periods. A shift of water uptake pattern towards deeper horizons was observed only at the end of the dry season after shrub defoliation. The mean depth of water uptake, as determined by the isotopic signature of stem water, was consistent with grass and shrub root profiles and with changes in soil water content profiles as surveyed by a neutron probe. This provides evidence for potentially strong competition between shrubs and grasses for soil water in these humid savannas. Limited nutrient availability may explain these competitive interactions. These results enhance our understanding of shrub-grass interactions , and will contribute to models of ecosystem functioning in humid savannas.

One of the fundamental problems in organizations is devising mechanisms for eliciting voluntary contributions (in terms of time, money, or effort) from individual members of a team that find themselves entrapped in a social dilemma situation. We present a structural solution to this problem that embeds the traditional within-group social dilemma in a between-group competition for an exogenously determined prize. Our analysis implies that this competition provides an incentive to contribute, thereby reducing free riding. Contrary to existing literature, we focus on 1) asymmetric competitions where team sizes are not identical, and 2) competitions between more than two teams.

We propose an intergroup competition scheme (ICS) to solve the free-riding problem in the public goods game. Our solution only requires knowledge of the group contributions, is budget balanced and with the right parameters a dominant strategy. The main innovations of our design are that the prize to the winning group is paid by the losing group and that the size of the transfer depends on the difference in contribution by the two groups. With the right parameters, this scheme changes the dominant strategy from none to full contribution. We tested different parameterizations for the ICS. The experiments show dramatic gains in efficiency in all the ICS treatments. Moreover, versions of the ICS in which intergroup competition should not change the zero contribution Nash equilibrium also produce remarkable gains in efficiency and no decline in contributions over time.

We propose an intergroup competition scheme (ICS) to solve the free-riding problem in the public goods game. Our solution only requires knowledge of the group contributions, is budget balanced and with the right parameters a dominant strategy. The main innovations of our design are that the prize to the winning group is paid by the losing group and that the size of the transfer depends on the difference in contribution by the two groups. With the right parameters, this scheme changes the dominant strategy from none to full contribution. We tested different parameterizations for the ICS. The experiments show dramatic gains in efficiency in all the ICS treatments. Moreover, versions of the ICS in which intergroup competition should not change the zero contribution Nash equilibrium also produce remarkable gains in efficiency and no decline in contributions over time.

We experimentally investigate the effect of intergroup competitionwith/out monetary incentives to winon intragroup cooperation. In one-shot games, competition increases cooperation with/out incentives. In finitely repeated games, cooperation is sustained with incentives. Cooperation decreases (increases) in response to wins (losses).

One of the fundamental problems in organizations is devising mechanisms for eliciting voluntary contributions (in terms of time, money, or effort) from individual members of a team that find themselves entrapped in a social dilemma situation. We present a structural solution to this problem that embeds the traditional within-group social dilemma in a between-group competition for an exogenously determined prize. Our analysis implies that this competition provides an incentive to contribute, thereby reducing free riding. Contrary to existing literature, we focus on 1) asymmetric competitions where team sizes are not identical, and 2) competitions between more than two teams.

Using the real-time protocol of play-a relatively new experimental mechanism in which the order of play and timing of decisions are determined endogenously-we investigate voluntary contributions to the provision of pure public goods. We consider the case where the good is binary, players are asymmetric, communication is prohibited, and all-or-none contributions to the public good can be withdrawn at any time during the round of play. Our results: (1) support an equilibrium in which contributors maximize the sum of their own payoffs; (2) show considerably higher levels of contribution than under the more commonly used simultaneous protocol of play; and (3) exhibit no decrease in level of contribution across multiple iterations of the stage game. On comparing our results to those of , we conclude that modifying the mechanism so that contributions once made cannot be revoked yields significantly higher levels of contribution over the course of the game.

Tacit coordination is studied in a class of games in which each of n = 20 players is required to choose between two courses of actions. The first action offers each player a fixed outcome whereas the second presents her the opportunity of participating in a lottery with probabilities that are determined endogenously. Across multiple iterations of the game and trial-to-trial changes in the composition of the lottery, we observe a remarkably good coordination on the aggregate but not individual level. We further observe systematic deviations from the Nash equilibrium solution that are accounted for quite well by a simple adaptive learning model.

Your article is protected by copyright and all rights are held exclusively by International Union for the Study of Social Insects (IUSSI). This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".

What motivates individual self-sacrificial behavior in intergroup conflicts? Is it the altruistic desire to help the in-group or the aggressive drive to hurt the outgroup? This article introduces a new game paradigm, the intergroup prisoner's dilemma-maximizing difference (IPD-MD) game, designed specifically to distinguish between these two motives. The game involves two groups. Each group member is given a monetary endowment and can decide how much of it to contribute. Contribution can be made to either of two pools, one that benefits the ingroup at a personal cost and another that, in addition, harms the out-group. An experiment demonstrated that contributions in the IPD-MD game are made almost exclusively to the cooperative, within-group pool. Moreover, preplay intragroup communication increases intragroup cooperation, but not intergroup competition. These results are compared with those observed in the intergroup prisoner's dilemma game, in which group members' contributions are restricted to the competitive, between-group pool.

We report experimental data from a two-player, two-action unprofitable game with an unique mixed strategy equilibrium. Our design allows subjects to explicitly choose probability distributions over actions. Patterns of play differ greatly from the mixed strategy equilibrium and the maxmin strategy profiles, both when measured as subjects' choices of probability distributions, and as the resulting actions played. The Quantal Response Equilibrium (QRE) concept is a good predictor of the subjects' average choices.

Tacit coordination is studied in a class of games in which each of n = 20 players is required to choose between two courses of actions. The first action offers each player a fixed outcome whereas the second presents her the opportunity of participating in a lottery with probabilities that are determined endogenously. Across multiple iterations of the game and trial-to-trial changes in the composition of the lottery, we observe a remarkably good coordination on the aggregate but not individual level. We further observe systematic deviations from the Nash equilibrium solution that are accounted for quite well by a simple adaptive learning model.

What motivates individual self-sacrificial behavior in intergroup conflicts? Is it the altruistic desire to help the in-group or the aggressive drive to hurt the outgroup? This article introduces a new game paradigm, the intergroup prisoner's dilemma-maximizing difference (IPD-MD) game, designed specifically to distinguish between these two motives. The game involves two groups. Each group member is given a monetary endowment and can decide how much of it to contribute. Contribution can be made to either of two pools, one that benefits the ingroup at a personal cost and another that, in addition, harms the out-group. An experiment demonstrated that contributions in the IPD-MD game are made almost exclusively to the cooperative, within-group pool. Moreover, preplay intragroup communication increases intragroup cooperation, but not intergroup competition. These results are compared with those observed in the intergroup prisoner's dilemma game, in which group members' contributions are restricted to the competitive, between-group pool.

Costly individual participation in intergroup conflict can be motivated by ''in-group love''-a cooperative motivation to help the in-group, by ''out-group hate''-an aggressive or competitive motivation to hurt the out-group, or both. This study employed a recently developed game paradigm designed specifically to distinguish between these two motives. The game was played repeatedly between two groups with three players in each group. In addition, we manipulated the payoff structure of the interaction that preceded the game such that half of the groups experienced peaceful coexistence and the other half experienced heightened conflict prior to the game. Enabling group members to express in-group love independently of out-group hate significantly reduced intergroup conflict. Group members strongly preferred to cooperate within their group, rather than to compete against the out-group for relative standing, even in the condition in which the repeated game was preceded by conflict. Although both ''in-group love'' and ''out-group hate'' somewhat diminished as the game continued (as players became more selfish), choices indicative of the former motivation were significantly more frequent than choices indicative of the latter throughout the interaction. We discuss the implications of these findings for conflict resolution.

The personality - situation debate in psychology repeats itself in behavioral economics as the rational actor (equilibrium) versus type debate. This paper examines under which condition psychology overrides rational behavior and vice versa. If experimental subjects have insufficient information about the game they project their personality into the situation.