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Abstract:
During the last two decades economists have made much progress in understanding incentives, contracts and organisations. Yet, they constrained their attention to a very narrow and empirically questionable view of human motivation. The purpose of this paper is to show that this narrow view of human motivation may severely limit understanding the determinants and effects of incentives. Economists may fail to understand the levels and the changes in behaviour if they neglect motives like the desire to reciprocate or the desire to avoid social disapproval. We show that monetary incentives may backfire and reduce the performance of agents or their compliance with rules. In addition, these motives may generate very powerful incentives themselves.

Incentives, Contracts, Reciprocity, Social Approval, Social Norms, Intrinsic Motivation

Abstract:
Experimental games turned out to be remarkably productive tools for examining the nature of social preferences and social norms. This paper describes the methods and tools of experimental game
theory and provides a selection of games that have been useful. We also discuss the role of evolutionary explanations and of social preference theory in organizing the data in a coherent way.

Abstract:
Experimental games turned out to be remarkably productive tools for examining the nature of social preferences and social norms. This paper describes the methods and tools of experimental game
theory and provides a selection of games that have been useful. We also discuss the role of evolutionary explanations and of social preference theory in organizing the data in a coherent way.

Abstract:
In this paper we provide experimental evidence indicating that incentive contracts may cause a strong crowding out of voluntary cooperation. This crowding-out effect constitutes costs of incentive provision that have been largely neglected by economists. In our experiments the crowding-out effect is so strong that the incentive contracts are less efficient than contracts without any incentives. Principals, nonetheless, prefer the incentive contracts because they allow them to appropriate a much larger share of the (smaller) total surplus and are, hence, more profitable for them.

Incentive contracts, reciprocity, incomplete contracts, voluntary cooperation, experiments

Abstract:
In this paper we provide experimental evidence indicating that incentive contracts may cause a strong crowding out of reciprocity-driven voluntary cooperation. This crowding out effect constitutes costs of incentive provision that have been largely neglected by economists. In our experiments the crowding out effect is so strong that the incentive contracts are less efficient than contracts without any incentives. Principals, nonetheless, prefer the incentive contracts because they allow them to appropriate a much larger share of the (smaller) total surplus and are, hence, more profitable for them.

Incentive contracts, reciprocity, incomplete contracts, voluntary cooperation, experiments

Abstract:
Most economic models are based on the self-interest hypothesis that assumes that all people are exclusively motivated by their material self-interest. In recent years experimental economists have gathered overwhelming evidence that systematically refutes the self-interest hypothesis and suggests that many people are strongly motivated by concerns for fairness and reciprocity. Moreover, several theoretical Papers have been written showing that the observed phenomena can be explained in a rigorous and tractable manner. These theories in turn induced a new wave of experimental research offering additional exciting insights into the nature of preferences and into the relative performance of competing theories of fairness. The purpose of this Paper is to review these recent developments, to point out open questions, and to suggest avenues for future research.

Altruism, behavioural economics, competition, contracts, experiments, fairness, incentives, reciprocity

Abstract:
Most economic models are based on the self-interest hypothesis that assumes that all people are exclusively motivated by their material self-interest. In recent years experimental economists have gathered overwhelming evidence that systematically refutes the self-interest hypothesis and suggests that many people are strongly motivated by concerns for fairness and reciprocity. Moreover, several theoretical papers have been written showing that the observed phenomena can be explained in a rigorous and tractable manner. These theories in turn induced a new wave of experimental research offering additional exciting insights into the nature of preferences and into the relative performance of competing theories of fairness. The purpose of this paper is to review these recent developments, to point out open questions, and to suggest avenues for future research.

Behavioral Economics, Fairness, Reciprocity, Altruism, Experiments, Incentives, Contracts, Competition

Abstract:
This paper shows that reciprocity has powerful implications for many economic domains. It is an important determinant in the enforcement of contracts and social norms and enhances the possibilities of collective action greatly. Reciprocity may render the provision of explicit incentives inefficient because the incentives may crowd out voluntary co-operation. It strongly limits the effects of competition in markets with incomplete contracts and gives rise to noncompetitive wage differences. Finally, reciprocity it is also a strong force contributing to the existence of incomplete contracts.

Abstract:
A substantial number of people exhibit social preferences, which means they are not solely motivated by material self-interest but also care positively or negatively for the material payoffs of relevant reference agents. We show empirically that economists fail to understand fundamental economic questions when they disregard social preferences, in particular, that without taking social preferences into account, it is not possible to understand adequately (i) effects of competition on market outcomes, (ii) laws governing cooperation and collective action, (iii) effects and the determinants of material incentives, (iv) which contracts and property rights arrangements are optimal, and (v) important forces shaping social norms and market failures.

Abstract:
A substantial number of people exhibit social preferences, which means they are not solely motivated by material self-interest but also care positively or negatively for the material payoffs of relevant reference agents. We show empirically that economists fail to understand fundamental economic questions when they disregard social preferences, in particular, that without taking social preferences into account, it is not possible to understand adequately (i) the effects of competition on market outcomes, (ii) laws governing cooperation and collective action, (iii) effects and the determinants of material incentives, (iv) which contracts and property rights arrangements are optimal, and (v) important forces shaping social norms and market failures.

Abstract:
A substantial number of people exhibit social preferences, which means they are not solely motivated by material self-interest but also care positively or negatively for the material payoffs of relevant reference agents. We show empirically that economists fail to understand fundamental economic questions when they disregard social preferences, in particular, that without taking social preferences into account, it is not possible to understand adequately (i) the effects of competition on market outcomes, (ii) laws governing cooperation and collective action, (iii) effects and the determinants of material incentives, (iv) which contracts and property rights arrangements are optimal, and (v) important forces shaping social norms and market failures.

Abstract:
In this paper we provide experimental evidence indicating that incentive contracts may undermine voluntary cooperation. This suggests that explicit incentives may have costly side effects that have been largely neglected by economists. In our experiments the undermining effect is so strong that the incentive contracts are less efficient than contracts without any incentives. Buyers, who are in the role of principals, nonetheless, prefer the incentive contracts because they allow them to appropriate a much larger share of the (smaller) total surplus and are, hence, more profitable for them. The undermining of voluntary cooperation through incentives is, in principle, consistent with models of inequity aversion and reciprocity. Additional experiments show, however, that the reduction of voluntary cooperation through incentives is partly due to a framing effect. If the incentive is framed as a price deduction the reduction of voluntary cooperation is much stronger compared to a situation where the incentive is framed as a bonus paid on top of a base price.

incentive contracts, reciprocity, incomplete contracts, voluntary cooperation, experiments

Abstract:
There is strong evidence that people exploit their bargaining power in competitive markets but not in bilateral bargaining situations. There is also strong evidence that people exploit free-riding opportunities in voluntary cooperation games. Yet, when they are given the opportunity to punish free riders, stable cooperation is maintained although punishment is costly for those who punish. This paper asks whether there is a simple common principle that can explain this puzzling evidence. We show that if a fraction of the people exhibits inequality aversion the puzzles can be resolved.

Abstract:
We show that concerns for fairness may have dramatic consequences for the optimal provision of incentives in a moral hazard context. Incentive contracts that are optimal when there are only selfish actors become inferior when some agents are concerned with fairness. Conversely, contracts that are doomed to fail when there are only selfish actors provide powerful incentives and become superior when there are also fair-minded players. These predictions are strongly supported by the results of a series of experiments. Furthermore, our results suggest that the existence of fair actors may be an important reason why many contracts are left deliberately incomplete.

Fairness, incentive contracts, incomplete contracts, moral hazard, reciprocity

Abstract:
We show that concerns for fairness may have dramatic consequences for the optimal provision of incentives in a moral hazard context. Incentive contracts that are optimal when there are only selfish actors become inferior when some agents are concerned about fairness. Conversely, contracts that are doomed to fail when there are only selfish actors provide powerful incentives and become superior when there are also fair-minded players. These predictions are strongly supported by the results of a series of experiments. Furthermore, our results suggest that the existence of fair actors may be an important reason why many contracts are left deliberately incomplete.

Incentive Contracts, Moral Hazard, Fairness, Reciprocity, Incomplete Contracts

Abstract:
This paper provides evidence that free riders are heavily punished even if punishment is costly and does not provide any material benefits for the punisher. The more free riders negatively deviate from the group standard the more they are punished. As a consequence, the existence of an opportunity for costly punishment causes a large increase in cooperation levels because potential free riders face a credible threat. We show, in particular, that in the presence of a costly punishment opportunity almost complete cooperation can be achieved and maintained although, under the standard assumptions of rationality and selfishness, there should be no cooperation at all. We also show that free riding causes strong negative emotions among cooperators. The intensity of these emotions is the stronger the more the free riders deviate from the group standard. Our results provide, therefore, support for the hypothesis that emotions are guarantors of credible threats.

Voluntary Cooperation, Public Good, Punishment, Emotions, Social Norms, Experiments

Abstract:
This paper provides evidence that free riders are heavily punished even if punishment is costly and does not provide any material benefits for the punisher. The more free riders negatively deviate from the group standard the more they are punished. As a consequence, the existence of an opportunity for costly punishment causes a large increase in cooperation levels because potential free riders face a credible threat. We show, in particular, that in the presence of a costly punishment opportunity almost complete cooperation can be achieved and maintained although, under the standard assumptions of rationality and selfishness, there should be no cooperation at all. We also show that free riding causes strong negative emotions among cooperators. The intensity of these emotions is the stronger the more the free riders deviate from the group standard. Our results provide, therefore, support for the hypothesis that emotions are guarantors of credible threats.

Abstract:
Recently developed models of fairness can explain a wide variety of seemingly contradictory facts. The most controversial and yet unresolved issue in the modeling of fairness preferences concerns the behavioral relevance of fairness intentions. Intuitively, fairness intentions seem to play an important role in economic relations, political struggles and legal disputes. Yet, so far there is little rigorous evidence supporting this intuition. In this paper we provide clear and unambiguous experimental evidence for the behavioral relevance of fairness intentions. Our results indicate that the attribution of fairness intentions is important both in the domain of negatively reciprocal behavior and in the domain of positively reciprocal behavior. This means that reciprocal behavior cannot be fully captured by equity models that are exclusively based on preferences over the distribution of material payoffs. Models that take into account players' fairness intentions and distributional preferences are consistent with our data while models that focus exclusively on intentions or on the distribution of material payoffs are not.

Fairness, Reciprocity, Intentions, Experiments, Moonlighting Game

Abstract:
Informal sanctions are a major determinant of a society's social capital because they are key to the enforcement of implicit agreements and social norms. Yet, little is known about the driving forces behind informal sanctions. We examine systematically the determinants of informal sanctions by a large number of experiments. Our findings show that the violation of fairness principles is the most important driving force of sanctions but, in addition, a non-negligible part of the sanctions is driven by spitefulness. We find surprisingly little evidence for strategic sanctions that are imposed to create future material benefits. Within the class of fairness-driven sanctions the motive to harm those who committed unfair actions or who revealed unfair intentions seems most important. The motive to decrease unfair payoff differences also plays some role but it cannot explain a sizeable part of the sanctions. The motive to achieve a fair relative share is largely irrelevant for sanctioning behavior.

Informal Sanction, Social Norm, Social Capital, Strategic Sanction, Fairness, Reciprocity, Spitefulness.

Abstract:
This paper presents an experimental examination of the Falkinger (1996) mechanism for overcoming the free-rider problem. The basic idea of the mechanism is that deviations from the mean contribution to the public good are taxed and subsidized. The mechanism has attractive properties because (i) it induces higher contributions to the public good and can implement an efficient level of contributions as a Nash equilibrium, (ii) the government budget is always balanced irrespective of the level of individual contributions, (iii) it is simple and policy makers need only little information to implement the mechanism.

To examine the empirical properties of the mechanism we conducted a large series of experiments. It turns out that the introduction of the mechanism generates immediate and large efficiency gains. This result is robust throughout many different experimental settings. Moreover, in the presence of the mechanism the Nash equilibrium is a rather good predictor of behavior.

Abstract:
Most previous studies on intertemporal labor supply found very small or insignificant substitution effects. It is not clear, however, whether these results are due to institutional constraints on workers' labor supply choices or whether the behavioral assumptions of the standard life cycle model with time separable preferences are empirically invalid. We conducted a randomized field experiment in a setting in which workers were free to choose their working times and their efforts during working time. We document a large positive wage elasticity of overall labor supply and an even larger wage elasticity of labor hours, which implies that the wage elasticity of effort per hour is negative.

While the standard life cycle model cannot explain the negative effort elasticity, we show that a modified neoclassical model with preference spillovers across periods and a model with reference dependent, loss averse preferences are consistent with the evidence. With the help of a further experiment we can show that only loss averse individuals exhibit a significantly negative effort response to the wage increase and that the degree of loss aversion predicts the size of the negative effort response.

Abstract:
This paper examines how the presence of a non-negligible fraction of reciprocally fair actors changes the provision of incentives through contracts. We provide experimental evidence that principals have a strong preference for less complete contracts although the standard self-interest model predicts that they should prefer the more complete contract. Our theoretical analysis shows that fairness concerns can explain this preference for less completeness. Fair principals keep their promises which provides strong pecuniary incentives through an incomplete contract. Selfish principals free-ride and exploit the agents. Counter-intuitively, selfish agents are induced to work by an incomplete contract while fair agents shirk.

Abstract:
We show experimentally that fairness concerns may have a decisive impact on both the actual and the optimal choice of contracts in a moral hazard context. Explicit incentive contracts that are optimal according to self-interest theory become inferior when some agents value fairness. Conversely, implicit bonus contracts that are doomed to fail among purely selfish actors provide powerful incentives and become superior when there are some fair-minded players. The principals understand this and predominantly choose the bonus contracts, even preferring a pure bonus contract over a contract that combines the enforcement power of explicit and implicit incentives. This contract preference is associated with the fact that explicit incentives weaken the enforcement power of implicit bonus incentives significantly. Our results are largely consistent with recently developed theories of fairness, which also offer interesting new insights into the interaction of contract choices, fairness and incentives.

Moral hazard, incentives, bonus contract, fairness, inequity aversion

Abstract:
In this chapter we provide a selective survey of experiments to investigate the potential of social motivations in explaining labour market phenomena. We argue that laboratory experiments are a useful instrument to explore issues in labour market theory and personnel economics. Our starting point is the observation that employment relations are frequently governed by incomplete contracts. We show that the norm of reciprocity that leads to gift exchanges is an effective contract enforcement device under conditions of contractual incompleteness. We then present evidence that gift exchange can explain various labour market phenomena that are puzzles from the viewpoint of standard economic theory. Further issues in the related field of personnel economics that have by now been subjected to an experimental scrutiny concern characteristics of the employment relation and the issues of motivation and incentives systems. We conclude by pointing out the complementary nature of experiments to more conventional methods of data gathering.

Abstract:
We report on several experiments on the optimal allocation of ownership rights. The experiments confirm the property rights approach by showing that the ownership structure affects relationship-specific investments and that subjects attain the most efficient ownership allocation despite starting from different initial conditions. However, in contrast to the property rights approach, the most efficient ownership structure is joint ownership. These results are neither consistent with the self-interest model nor with models that assume that all people behave fairly, but they can be explained by the theory of inequity aversion that focuses on the interaction between selfish and fair players.

Ownership rights, double moral hazard, fairness, reciprocity, incomplete contracts

Abstract:
We report on several experiments on the optimal allocation of ownership rights. The experiments confirm the property rights approach by showing that the ownership structure affects relationship-specific investments and that subjects attain the most efficient ownership allocation despite starting from different initial conditions. However, in contrast to the property rights approach, the most efficient ownership structure is joint ownership. These results are neither consistent with the self-interest model nor with models that assume that all people behave fairly, but they can be explained by the theory of inequity aversion that focuses on the interaction between selfish and fair players.

Ownership rights, double moral hazard, fairness, reciprocity, incomplete contracts

Abstract:
The most fundamental solution concepts in Game Theory - Nash equilibrium, backward induction, and iterated elimination of dominated strategies - are based on the assumption that people are capable of predicting others' actions. These concepts require people to be able to view the game from the other players' perspectives, i.e., to understand others' motives and beliefs. Economists still know little about what enables people to put themselves into others' shoes and how this ability interacts with their own preferences and beliefs. Social neuroscience provides insights into the neural mechanism underlying our capacity to represent others' intentions, beliefs, and desires, referred to as 'Theory of Mind' or 'mentalizing', and the capacity to share the feelings of others, referred to as 'empathy'. We summarize the major findings about the neural basis of mentalizing and empathizing and discuss some implications for economics.

Neuroeconomics, mind reading, empathy

Abstract:
The most fundamental solution concepts in Game Theory - Nash equilibrium, backward induction, and iterated elimination of dominated strategies - are based on the assumption that people are capable of predicting others' actions. These concepts require people to be able to view the game from the other players' perspectives, i.e. to understand others' motives and beliefs. Economists still know little about what enables people to put themselves into others' shoes and how this ability interacts with their own preferences and beliefs. Social neuroscience provides insights into the neural mechanism underlying our capacity to represent others' intentions, beliefs, and desires, referred to as "Theory of Mind" or "mentalizing", and the capacity to share the feelings of others, referred to as "empathy". We summarize the major findings about the neural basis of mentalizing and empathizing and discuss some implications for economics.

Neuroeconomics, Mind Reading, Empathy

Abstract:
We examine experimentally how Chief Executive Officers (CEOs) respond to incentives and how they provide incentives in situations requiring trust and trustworthiness. As a control we compare the behavior of CEOs with the behavior of students. We find that CEOs are considerably more trusting and exhibit more trustworthiness than students - thus reaching substantially higher efficiency levels than students. Moreover, we find that, for CEOs as well as for students, incentives based on explicit threats to penalize shirking backfire by inducing less trustworthy behavior - giving rise to hidden costs of incentives. However, the availability of penalizing incentives also creates hidden returns: If a principal expresses trust by voluntarily refraining from implementing the punishment threat, the agent exhibits significantly more trustworthiness than if the punishment threat is not available. Thus trust seems to reinforce trustworthy behavior. Overall, trustworthiness is highest if the threat to punish is available but not used, while it is lowest if the threat to punish is used. Paradoxically, however, most CEOs and students use the punishment threat, although CEOs use it significantly less.

Abstract:
We provide experimental evidence that contractual incompleteness, ie, the absence of third party enforcement of workers' effort or the quality of the good traded causes a fundamental change in the nature of market interactions. If contracts are complete the vast majority of trades are initiated by public offers. Most trades take place in one-shot transactions and the contracting parties are indifferent with regard to the identity of their trading partner. Moreover, the short side of the market attempts to appropriate the whole gains from trade, which causes much disagreement about contract terms. If contracts are incomplete the vast majority of trades are initiated by private offers. The contracting parties form long-term relations and the provision of low effort or bad quality is penalized by the termination of the relationship. The threat of terminating the relation turns out to be an extremely powerful discipline device. Markets with incomplete contracts resemble a collection of bilateral trading islands rather than a competitive market. The short side of the market shares the gains from trade with the long side of the market so that there is little disagreement about contract terms. Our results support theories of the labour market that are based on the idea that unemployment is a worker discipline device.

Market interaction, contract enforcement, incomplete contract, involuntary unemployment, repeated transaction, fairness preferences

Abstract:
We provide experimental evidence that contractual incompleteness, i.e., the absence of third party enforcement of workers' effort or the quality of the good traded, causes a fundamental change in the nature of market interactions. If contracts are complete the vast majority of trades are initiated by public offers. Most trades take place in one-shot transactions and the contracting parties are indifferent with regard to the identity of their trading partner. Moreover, the short side of the market attempts to appropriate the whole gains from trade, which causes much disagreement about contract terms. If contracts are incomplete the vast majority of trades are initiated by private offers. The contracting parties form long-term relations and the provision of low effort or bad quality is penalized by the termination of the relationship. The threat of terminating the relation turns out to be an extremely powerful discipline device. Markets with incomplete contracts resemble a collection of bilateral trading islands rather than a competitive market. The short side of the market shares the gains from trade with the long side of the market so that there is little disagreement about contract terms. Our results support theories of the labor market that are based on the idea that unemployment is a worker discipline device.

Market Interaction, Contract Enforcement, Incomplete Contract, Involuntary Unemployment, Repeated Transaction, Fairness Preferences

Abstract:
There is abundant evidence that many individuals violate the rationality assumptions routinely made in economics. However, powerful evidence also indicates that violations of individual rationality do not necessarily refute the aggregate predictions of standard economic models that assume full rationality of all agents. Thus, a key question is how the interactions between rational and irrational people shape the aggregate outcome in markets and other institutions. We discuss evidence indicating that strategic complementarity and strategic substitutability are decisive determinants of aggregate outcomes. Under strategic complementarity, a small amount of individual irrationality may lead to large deviations from the aggregate predictions of rational models, whereas a minority of rational agents may suffice to generate aggregate outcomes consistent with the predictions of rational models under strategic substitutability.

Irrationality, Rationality, Anomaly, Aggregate Outcome, Competitive Markets, Money Illusion, Base Rate Fallacy

Abstract:
In this Paper we show that a simple model of fairness preferences explains major experimental regularities of common pool resource (CPR) experiments. The evidence indicates that in standard CPR games without communication and without sanctioning possibilities inefficient excess appropriation is the rule. When communication or informal sanctions are available, however, appropriation behaviour is more efficient. Our analysis shows that these regularities arise naturally when a fraction of the subjects exhibits reciprocal preferences.

Common pool resources, experiments, fairness, reciprocity, game theory, fairness models

Abstract:
In this paper we show that a simple model of reciprocal preferences explains major experimental regularities of common pool resource (CPR) experiments. The evidence indicates that in standard CPR games without communication and without sanctioning possibilities inefficient excess appropriation is the rule. However, when communication or informal sanctions are available appropriation behavior is more efficient. Our analysis shows that these regularities arise naturally when a fraction of the subjects exhibits reciprocal preferences.

Common Pool Resources, Experiments, Fairness, Reciprocity, Game Theory, Fairness Models

Abstract:
Many of the most important choices in people's lives have an inter-temporal dimension, i.e., these choices are associated with a flow of benefits or costs that accrue in the future. In addition, such choices are frequently habit-forming. Yet, little is known about habit-forming inter-temporal choice behavior. This paper reports the results of an inter-temporal choice experiment with habit-formation. Subjects' choices deviate systematically from individually optimal decisions in the direction of over-consumption. This over-consumption is partly driven by loss avoidance, comparable to a real life situation in which addicted people consume addictive substances only in order to overpower withdrawal symptoms. Our results thus reject the theory of rational addiction.

Abstract:
Economists long considered money illusion to be largely irrelevant. Here we show, however, that money illusion has powerful effects on equilibrium selection. If we represent pay-offs in nominal terms, choices converge to the Pareto inefficient equilibrium; however, if we lift the veil of money by representing pay-offs in real terms, the Pareto efficient equilibrium is selected. We also show that strategic uncertainty about the other players' behaviour is key for the equilibrium selection effects of money illusion: even though money illusion vanishes over time if subjects are given learning opportunities in the context of an individual optimization problem, powerful and persistent effects of money illusion are found when strategic uncertainty prevails.

Money illusion, coordination failure, equilibrium selection, multiple equilibria, coordination games

Abstract:
Economists long considered money illusion to be largely irrelevant. Here we show, however, that money illusion has powerful effects on equilibrium selection. If we represent payoffs in nominal terms, choices converge to the Pareto inefficient equilibrium; however, if we lift the veil of money by representing payoffs in real terms, the Pareto efficient equilibrium is selected. We also show that strategic uncertainty about the other players' behavior is key for the equilibrium selection effects of money illusion: even though money illusion vanishes over time if subjects are given learning opportunities in the context of an individual optimization problem, powerful and persistent effects of money illusion are found when strategic uncertainty prevails.

money illusion, coordination failure, equilibrium selection, multiple equilibria, coordination games

Abstract:
In recent years a large number of experimental studies have documented the existence of strong reciprocity among humans. Strong reciprocity means that people willingly repay gifts and punish the violation of cooperation and fairness norms even in anonymous one-shot encounters with genetically unrelated strangers. We provide ethnographic and experimental evidence suggesting that ultimate theories of kin selection, reciprocal altruism, costly signaling and indirect reciprocity do not provide satisfactory evolutionary explanations of strong reciprocity. The problem of these theories is that they can rationalize strong reciprocity only if it is viewed as maladaptive behavior whereas the evidence suggests that it is an adaptive trait. Thus, we conclude that alternative evolutionary approaches are needed to provide ultimate accounts of strong reciprocity.

Abstract:
This Paper shows that identical offers in an ultimatum game generate systematically different rejection rates depending on the other offers that are available to the proposer. This result casts doubt on the consequentialist practice in economics of defining the utility of an action solely in terms of the consequences of the action irrespective of the set of alternatives. It means, in particular, that negatively reciprocal behavior cannot be fully captured by equity models that are exclusively based on preferences over the distribution of material pay-offs. Models that take into account players' fairness intentions and distributional preferences are consistent with our data while models that focus exclusively on intentions or on the distribution of material pay-offs are not.

Fairness, intentions, models of fairness

Abstract:
This paper shows that identical offers in an ultimatum game generate systematically different rejection rates depending on the other offers that are available to the proposer. This result casts doubt on the consequentialist practice in economics to define the utility of an action solely in terms of the consequences of the action irrespective of the set of alternatives. It means, in particular, that negatively reciprocal behavior cannot be fully captured by equity models that are exclusively based on preferences over the distribution of material payoffs. Models that take into account players' fairness intentions and distributional preferences are consistent with our data while models that focus exclusively on intentions or on the distribution of material payoffs are not.

Abstract:
This paper shows that identical offers in an ultimatum game generate systematically different rejection rates depending on the other offers that are available to the proposer. This result casts doubt on the consequentialist practice in economics to define the utility of an action solely in terms of the consequences of the action irrespective of the set of alternatives. It means, in particular, that negatively reciprocal behavior cannot be fully captured by equity models that are exclusively based on preferences over the distribution of material payoffs. Models that take into account players' fairness intentions and distributional preferences are consistent with our data while models that focus exclusively on intentions or on the distribution of material payoffs are not.

Abstract:
Typically, laboratory experiments suffer from homogeneous subject pools and selfselection biases. The usefulness of survey data is limited by measurement error and by the questionability of their behavioral relevance. Here we present a method integrating interactive experiments and representative surveys thereby overcoming crucial weaknesses of both approaches. One of the major advantages of our approach is that it allows for the integration of experiments, which require interaction among the participants, with a survey of non-interacting respondents in a smooth and inexpensive way. We illustrate the power of our approach with the analysis of trust and trustworthiness in Germany by combining representative survey data with representative behavioral data from a social dilemma experiment. We identify which survey questions intended to elicit people's trust correlate well with behaviorally exhibited trust in the experiment. People above the age of 65, highly skilled workers and people living in bigger households exhibit less trusting behavior. Foreign citizens, Catholics and people favoring the Social Democratic Party or the Christian Democratic Party exhibit more trust. People above the age of 65 and those in good health behave more trustworthy or more altruistically, respectively. People below the age of 35, the unemployed and people who say they are in favor of none of the political parties behave less trustworthy or less altruistically, respectively.

Experiment, Survey, Trust, Trustworthiness, Altruism

Abstract:
We provide evidence that long-term relationships between trading parties emerge endogenously in the absence of third party enforcement of contracts and are associated with a fundamental change in the nature of market interactions. Without third party enforcement, the vast majority of trades are initiated with private offers and the parties share the gains from trade equally. Low effort or bad quality is penalized by the termination of the relationship, wielding a powerful effect on contract enforcement. Successful long-term relations exhibit generous rent sharing and high effort (quality) from the very beginning of the relationship. In the absence of third-party enforcement, markets resemble a collection of bilateral trading islands rather than a competitive market. If contracts are third party enforceable, rent sharing and long-term relations are absent and the vast majority of trades are initiated with public offers. Most trades take place in one-shot transactions and the contracting parties are indifferent with regard to the identity of their trading partner.

relational contracts, implicit contracts, market interaction, involuntary unemployment, repeated transaction, fairness preferences

Abstract:
This paper discusses recent neuroeconomic evidence related to other- regarding behaviors and the decision to trust in other people's other-regarding behavior. This evidence supports the view that people derive nonpecuniary utility (i) from mutual cooperation in social dilemma (SD) games and (ii) from punishing unfair behavior. Thus, mutual cooperation and the punishment of free riders in SD games is not irrational, but better understood as rational behavior of people with corresponding social preferences. We also report the results of a recent study that examines the impact of the neuropeptide Oxytocin (OT) on trusting and trustworthy behavior in a sequential SD. Animal studies have identified Oxytocin as a hormone that induces prosocial approach behavior, suggesting that it may also affect prosocial behavior in humans. Indeed, the study shows that subjects given Oxytocin exhibit much more trusting behavior, suggesting that OT has a direct impact on certain aspects of subjects' social preferences. Interestingly, however, although Oxytocin affects trusting behavior, it has no effect on subjects' trustworthiness.

Neuroeconomic , Foundations of Trust, Social Preferences

Abstract:
We study the importance of conditional cooperation in a one-shot public goods game by using a variant of the strategy-method. We find that a third of the subjects can be classified as free riders, whereas 50 percent are conditional cooperators.

voluntary contributions, conditional cooperation, reciprocity, free riding, strategy-method, experiments

Abstract:
This paper reports on a two-task principal-agent experiment in which only one task is contractible. The principal can either offer a piece-rate contract or a (voluntary) bonus to the agent. Bonus contracts strongly outperform piece rate contracts. Many principals reward high efforts on both tasks with substantial bonuses. Agents anticipate this and provide high efforts on both tasks. In contrast, almost all agents with a piece rate contract focus on the first task and disregard the second. Principals understand this and predominantly offer bonus contracts. This behavior contradicts the self-interest theory but is consistent with theories of fairness.

Incentives, moral hazard, multiple tasks, fairness, experiments

Abstract:
One of the most basic questions in economics concerns the effects of competition on market prices. We show that the neglect of both fairness concerns and decision errors prevents a satisfactory understanding of how competition affects prices. We conducted experiments which demonstrate that the introduction of even a very small amount of competition to a bilateral exchange situation - by adding just one competitor induces large behavioral changes among buyers and sellers, causing large changes in market prices. Models that assume that all people are self-interested and fully rational fail to explain these changes satisfactorily. In contrast, a model that combines heterogeneous fairness concerns with decision errors predicts all comparative static effects of changes in competition correctly. Moreover, the combined model enables us to predict the entire distribution of prices in many different competitive situations remarkably well.

Competition, Fairness, Reciprocity, Quantal Response Equilibrium

Abstract:
The evidence from many experiments suggests that people are heterogeneous with regard to their abilities to make rational, forward looking, decisions. This raises the question when the rational types are decisive for aggregate outcomes and when the boundedly rational types shape aggregate results. We examine this question in the context of a long-standing and important economic problem - the adjustment of nominal prices after an anticipated money shock. Our experiments show that when agents' actions are strategic substitutes adjustment to the new equilibrium is extremely quick whereas under strategic complementarity adjustment lasts very long and is associated with relatively large real effects. This adjustment difference occurs because price expectations are very flexible under substitutability and very sticky under complementarity. Our results suggest that strategic complementarity does not only provide incentives for the rational types to partly mimic the behavior of the boundedly rational types but it also renders people less rational and forward looking. In addition, under complementarity people attribute less rationality to the other players.

Abstract:
In recent years, many social scientists have claimed that trust plays an important role in economic and social transactions. Despite its proposed importance, the measurement and the definition of trust seem to be not fully settled, and the identification of the exact role of trust in economic interactions has proven to be elusive. It is still not clear whether trust is just an epiphenomenon of good institutions or whether it plays an independent causal role capable of shaping important aggregate economic outcomes. In this paper, I rely on a behavioral definition of trust that enables us to relate it to economic primitives such as preferences and beliefs. I review strong biological and behavioral evidence indicating that trusting is not just a special case of risk-taking, but based on important forms of social preferences such as betrayal aversion. Behaviorally defined trust also opens the door for understanding national and ethnic trust differences in terms of differences in preferences and beliefs, and it suggests ways to examine and interpret a causal role of trust.

Abstract:
In recent years, many social scientists have claimed that trust plays an important role in economic and social transactions. Despite its proposed importance, the measurement and the definition of trust seem to be not fully settled, and the identification of the exact role of trust in economic interactions has proven to be elusive. It is still not clear whether trust is just an epiphenomenon of good institutions or whether it plays an independent causal role capable of shaping important aggregate economic outcomes. In this paper, I rely on a behavioral definition of trust that enables us to relate it to economic primitives such as preferences and beliefs. I review strong biological and behavioral evidence indicating that trusting is not just a special case of risk-taking, but based on important forms of social preferences such as betrayal aversion. Behaviorally defined trust also opens the door for understanding national and ethnic trust differences in terms of differences in preferences and beliefs, and it suggests ways to examine and interpret a causal role of trust.

trust, preferences, beliefs, biological basis

Abstract:
This paper shows that reciprocity has powerful implications for many economic domains. It is an important determinant in the enforcement of contracts and social norms and enhances the possibilities of collective action greatly. Reciprocity may render the provision of explicit incentive inefficient because the incentives may crowd out voluntary co-operation. It strongly limits the effects to competition in markets with incomplete contracts and gives rise to noncompetitive wage differences. Finally, reciprocity it is also a strong force contributing to the existence of incomplete contracts.

Abstract:
Money illusion means that people behave differently when the same objective situation is represented in nominal terms rather than in real terms. This paper shows that seemingly innocuous differences in payoff representation cause pronounced differences in nominal price inertia indicating the behavioral importance of money illusion. In particular, if the payoff information is presented to subjects in nominal terms, price expectations and actual price choices after a fully anticipated negative nominal shock are much stickier than when payoff information is presented in real terms. In addition we show that money illusion causes asymmetric effects of negative and positive nominal shocks. While nominal inertia is quite substantial and long-lasting after a negative shock, it is rather small after a positive shock.

Money Illusion, Nominal Inertia, Sticky Prices, Non-Neutrality of Money

Abstract:
The canonical model of life-cycle labor supply predicts a positive response of labor supplied to transitory wage changes. We tested this prediction by conducting a randomized field experiment with bicycle messengers. In contrast to previous studies we can observe in which way working hours as well as effort respond to a wage increase and we have full control regarding the workers' anticipation of the wage increase. The evidence indicates that workers increase monthly working time and decrease their daily effort but since the working time effect dominates the effort effect overall labor supply increases. The decrease in daily effort contradicts the canonical model of intertemporal labor supply with time separable preferences, since the wage in our experiment directly rewarded effort. We show that a simple model of loss averse, reference dependent, preferences can account for both the increase in working time and the decrease in daily effort. Moreover, we elicit independent individual measures of loss aversion and show that workers who are more prone to loss aversion are more likely to reduce effort in response to higher wages. Our model and our results also reconcile the seemingly contradictory evidence reported in previous studies (Camerer et al. 1997, Oettinger 1999) of high frequency labor supply.

labor supply, intertemporal substitution, loss aversion

Abstract:
The prevailing labor market models assume that minimum wages do not affect the labor supply schedule. We challenge this view in this paper by showing experimentally that minimum wages have significant and lasting effects on subjects' reservation wages. The temporary introduction of a minimum wage leads to a rise in subjects' reservation wages that persists even after the minimum wage has been removed. Firms are therefore forced to pay higher wages after the removal of the minimum wage than before its introduction. As a consequence, the employment effects of removing the minimum wage are significantly smaller than are the effects of its introduction. The impact of minimum wages on reservation wages may also explain the anomalously low utilization of sub-minimum wages if employers are given the opportunity of paying less than a minimum wage previously introduced. It may further explain why employers often increase workers' wages after an increase in the minimum wage by an amount exceeding that necessary for compliance with the higher minimum. At a more general level, our results suggest that economic policy may affect people's behavior by shaping the perception of what is a fair transaction and by creating entitlement effects.

Minimum wages, labor market, monopsony, fairness, reservation wages, entitlement

Abstract:
The prevailing labor market models assume that minimum wages do not affect the labor supply schedule. We challenge this view in this paper by showing experimentally that minimum wages have significant and lasting effects on subjects' reservation wages. The temporary introduction of a minimum wage leads to a rise in subjects' reservation wages which persists even after the minimum wage has been removed. Firms are therefore forced to pay higher wages after the removal of the minimum wage than before its introduction. As a consequence, the employment effects of removing the minimum wage are significantly smaller than are the effects of its introduction. The impact of minimum wages on reservation wages may also explain the anomalously low utilization of subminimum wages if employers are given the opportunity of paying less than a minimum wage previously introduced. It may further explain why employers often increase workers' wages after an increase in the minimum wage by an amount exceeding that necessary for compliance with the higher minimum. At a more general level, our results suggest that economic policy may affect people's behavior by shaping the perception of what is a fair transaction and by creating entitlement effects.

minimum wages, labor market, monopsony, fairness, reservation wages, entitlement

Abstract:
In a recent paper Engelmann and Strobl claim that a combination of a preference for efficiency and a Rawlsian motive for helping the least well-off is far more important than inequity aversion. Here we show that the relevance of the efficiency motive is largely restricted to students of economics and business administration. Students from other disciplines, adult academics from various disciplines and senior citizens value equality much higher than efficiency. Moreover, there is rather strong evidence that the relevance of the efficiency motive and the Rawlsian motive is largely restricted to non-strategic interactions.

Social Preferences, Inequity Aversion, Efficiency preferences

Abstract:
In many occupations workers' labor supply choices are constrained by institutional rules regulating labor time and effort provision. This renders explicit tests of the neoclassical theory of labor supply difficult. Here we present evidence from studies examining labor supply responses in "neoclassical environments" in which workers are free to choose when and how much to work. Despite the favorable environment the results cast doubt on the neoclassical model. They are, however, consistent with a model of reference dependent preferences exhibiting loss aversion and diminishing sensitivity.

labor supply, intertemporal substitution, loss aversion, reference dependent preferences

Abstract:
This paper reports the results of a series of competitive labour market experiments in which subjects have the possibility to reciprocate favours. In the high stake condition subjects earned between two and three times their monthly income during the experiment. In the normal stake condition the stake level was reduced by a factor of ten. We observe that both in the high and the normal stake condition fairness concerns are strong enough to outweigh competitive forces and give rise to non-competitive wages. There is also no evidence that effort behaviour becomes generally more selfish at higher stake levels. Therefore, our results suggest that, contrary to common beliefs, fairness concerns may play an important role even at relatively high stake levels.

Reciprocity, Fairness, Competitive Markets, Incentives, Stake Size

Abstract:
Informal sanctions are a major determinant of a society's social capital because they are key to the enforcement of implicit agreements and social norms. Yet, little is known about the driving forces behind informal sanctions. We systematically examine the determinants of informal sanctions by a large number of experiments. Our findings show that the violation of fairness principles is the most important driving force of sanctions but, in addition, a non-negligible part of the sanctions is driven by spitefulness. We find surprisingly little evidence for strategic sanctions that are imposed to create future material benefits. While non-strategic sanctions are of major importance in our experiments, strategic sanctions seem to play a negligible role. Within the class of fairness-driven sanctions the motive to harm those who committed unfair actions seems most important.

key-words: Informal Sanction, Social Norm, Social Capital, Strategic Sanction, Fairness, Reciprocity, Spitefulness

Abstract:
Recent studies found evidence for nominal wage rigidity during periods of relatively high nominal GDP growth. It has been argued, however, that in an environment with low nominal GDP growth, when nominal wage cuts become customary, workers' opposition to nominal cuts would erode and, hence, firms would no longer hesitate to reduce nominal pay. If this argument is valid nominal wage rigidity is largely irrelevant because in a high-growth environment there is little need to cut nominal pay while in a low-growth environment the necessary cuts would occur.

To examine this argument we use data from Switzerland where nominal GDP growth has been very low for many years in the 1990s. We find that the rigidity of nominal wages is a robust phenomenon that does not vanish in a low growth environment. In addition, it constitutes a considerable obstacle to real wage adjustments. In the absence of downward nominal rigidity, real wages would indeed be quite responsive to unemployment. Moreover, the wage sweep-ups caused by nominal rigidity are strongly correlated with unemployment suggesting that downward rigidity of nominal wages indeed contributes to unemployment.

Abstract:
In this paper, we argue that important labor market phenomena can be better understood if one takes (i) the inherent incompleteness and relational nature of most employment contracts and (ii) the existence of reference-dependent fairness concerns among a substantial share of the population into account. Theory shows and experiments confirm, that even if fairness concerns were only to exert weak effects in one-shot interactions, repeated interactions greatly magnify the relevance of such concerns on economic outcomes. We also review evidence from laboratory and field experiments examining the role of wages and fairness on effort, derive predictions from our approach for entry-level wages and incumbent workers' wages, confront these predictions with the evidence, and show that reference-dependent fairness concerns may have important consequences for the effects of economic policies such as minimum wage laws.

Abstract:
In this paper, we argue that important labor market phenomena can be better understood if one takes (i) the inherent incompleteness and relational nature of most employment contracts and (ii) the existence of reference-dependent fairness concerns among a substantial share of the population into account. Theory shows and experiments confirm, that even if fairness concerns were only to exert weak effects in one-shot interactions, repeated interactions greatly magnify the relevance of such concerns on economic outcomes. We also review evidence from laboratory and field experiments examining the role of wages and fairness on effort, derive predictions from our approach for entry-level wages and incumbent workers' wages, confront these predictions with the evidence, and show that reference-dependent fairness concerns may have important consequences for the effects of economic policies such as minimum wage laws.

fairness, contracts, wages, effort, experiments

Abstract:
This paper investigates the driving forces behind informal sanctions in cooperation games and the extent to which theories of fairness and reciprocity capture these forces. We find that cooperators' punishment is almost exclusively targeted towards the defectors but the latter also impose a considerable amount of spiteful punishment on the cooperators. However, spiteful punishment vanishes if the punishers can no longer affect the payoff differences between themselves and the punished individual, whereas the cooperators even increase the resources devoted to punishment in this case. Our data also discriminate between different fairness principles. Fairness theories that are based on the assumption that players compare their own payoff to the group's average or the group's total payoff cannot explain the fact that cooperators target their punishment at the defectors. Fairness theories assuming that players aim to minimize payoff inequalities cannot explain the fact that cooperators punish defectors even if payoff inequalities cannot be reduced. Therefore, retaliation, i.e., the desire to harm those who committed unfair acts, seems to be the most important motive behind fairness-driven informal sanctions.

sanctioning, cooperation, social norm, reciprocity, fairness, spitefulness

Abstract:
In a wide variety of settings, spiteful preferences would constitute an obstacle to cooperation, trade, and thus economic development. This paper shows that spiteful preferences - the desire to reduce another's material payoff for the mere purpose of increasing one's relative payoff - are surprisingly widespread in experiments conducted in one of the least developed regions in India (Uttar Pradesh). In a one-shot trust game, the authors find that a large majority of subjects punish cooperative behavior although such punishment clearly increases inequality and decreases the payoffs of both subjects. In experiments to study coordination and to measure social preferences, the findings reveal empirical patterns suggesting that the willingness to reduce another's material payoff - either for the sake of achieving more equality or for the sake of being ahead - is stronger among individuals belonging to high castes than among those belonging to low castes. Because extreme social hierarchies are typically accompanied by a culture that stresses status-seeking, it is plausible that the observed social preference patterns are at least partly shaped by this culture. Thus, an exciting question for future research is the extent to which different institutions and cultures produce preferences that are conducive or detrimental to economic development.

Economic Theory & Research, Access to Finance, Debt Markets, Bankruptcy and Resolution of Financial Distress, Gender and Social Development

Abstract:
In this paper we show that subtle forms of deceit undermine the effectiveness of incentives. We design an experiment in which the principal has an interest in underreporting the true performance difference between the agents in a dynamic tournament. According to the standard approach, rational agents should completely disregard the performance feedback of self-interested principals and choose their effort level as if they had not been given any information. However, despite substantial underreporting many principals seem to exhibit lying aversion which renders their feedback informative. Therefore, the agents respond to the feedback but discount it strongly by reducing their effort relative to fully truthful performance feedback. Moreover, previous experiences of being deceived exacerbate the problem and eventually reduce average effort even below the level that prevails in the absence of any feedback. Thus, both no feedback and truthful feedback are better for incentives than biased feedback.

Deception, Dishonesty, Communication, Cheap Talk, Dynamic Tournaments

Abstract:
In a recent paper, Hart and Moore (2008) introduce new behavioral assumptions that can explain long term contracts and important aspects of the employment relation. However, so far there exists no direct evidence that supports these assumptions and, in particular, Hart and Moore's notion that contracts provide reference points. In this paper, we examine experimentally the behavioral forces stipulated in their theory. The evidence confirms the model's prediction that there is a tradeoff between rigidity and flexibility in a trading environment with incomplete contracts and ex ante uncertainty about the state of nature. Flexible contracts - which would dominate rigid contracts under standard assumptions - cause a significant amount of shading on ex post performance while under rigid contracts much less shading occurs. Thus, although rigid contracts rule out trading in some states of the world, parties frequently implement them. While our results are broadly consistent with established behavioral concepts, they cannot easily be explained by existing theories. The experiment appears to reveal a new behavioral force: ex ante competition legitimizes the terms of a contract, and aggrievement and shading occur mainly about outcomes within the contract.

contracts, reference points, experiment

Abstract:
This paper examines the role of other-regarding and time preferences for cooperation in the field. We study the preferences of fishermen whose main, and often only, source of income stems from using a common pool resource (CPR). The exploitation of a CPR involves a negative interpersonal and inter-temporal externality because individuals who exploit the CPR reduce the current and the future yield for both others and themselves. Accordingly, economic theory predicts that more cooperative and more patient individuals should be less likely to exploit the CPR. Our data supports this prediction because fishermen who exhibit a higher propensity for cooperation in a laboratory public goods experiment, and those who show more patience in a laboratory time preference experiment, exploit the fishing grounds less in their daily lives. Moreover, because the laboratory public goods game exhibits no inter-temporal spillovers, measured time preferences should not predict cooperative behavior in the laboratory. This prediction is also borne out by our data. Thus, laboratory preference measures are useful to capture important dimensions of field behavior.

Cooperation, common pool resource, experiments, generalizability, methodology

Abstract:
This paper examines the role of other-regarding and time preferences for cooperation in the field. We study the preferences of fishermen whose main, and often only, source of income stems from using a common pool resource (CPR). The exploitation of a CPR involves a negative interpersonal and inter-temporal externality because individuals who exploit the CPR reduce the current and the future yield for both others and themselves. Accordingly, economic theory predicts that more cooperative and more patient individuals should be less likely to exploit the CPR. Our data supports this prediction because fishermen who exhibit a higher propensity for cooperation in a laboratory public goods experiment, and those who show more patience in a laboratory time preference experiment, exploit the fishing grounds less in their daily lives. Moreover, because the laboratory public goods game exhibits no inter-temporal spillovers, measured time preferences should not predict cooperative behavior in the laboratory. This prediction is also borne out by our data. Thus, laboratory preference measures are useful to capture important dimensions of field behavior.

cooperation, common pool resource, experiments, generalizability, methodology

Abstract:
We study the impact of reputational incentives in markets characterized by moral hazard problems. Social preferences have been shown to enhance contract enforcement in these markets, while at the same time generating considerable wage and price rigidity. Reputation powerfully amplifies the positive effects of social preferences on contract enforcement by increasing contract efficiency substantially. This effect is, however, associated with a considerable bilateralisation of market interactions, suggesting that it may aggravate price rigidities. Surprisingly, reputation in fact weakens the wage and price rigidities arising from social preferences. Thus, in markets characterized by moral hazard, reputational incentives unambiguously increase mutually beneficial exchanges, reduce rents, and render markets more responsive to supply and demand shocks.

Reputation, Reciprocity, Relational Contracts, Price Rigidity, Wage Rigidity

Abstract:
We study the impact of reputational incentives in markets characterized by moral hazard problems. Social preferences have been shown to enhance contract enforcement in these markets, while at the same time generating considerable wage and price rigidity. Reputation powerfully amplifies the positive effects of social preferences on contract enforcement by increasing contract efficiency substantially. This effect is, however, associated with a considerable bilateralisation of market interactions, suggesting that it may aggravate price rigidities. Surprisingly, reputation in fact weakens the wage and price rigidities arising from social preferences. Thus, in markets characterized by moral hazard, reputational incentives unambiguously increase mutually beneficial exchanges, reduce rents, and render markets more responsive to supply and demand shocks.

wage rigidity, price rigidity, relational contracts, reciprocity, reputation

Abstract:
During the last two decades economists have made much progress in understanding incentives, contracts and organizations. Yet, they constrained their attention to a very narrow and empirically questionable view of human motivation. The purpose of this Paper is to show that this narrow view of human motivation may severely limit understanding the determinants and effects of incentives. Economists may fail to understand the levels and the changes in behavior if they neglect motives like the desire to reciprocate or the desire to avoid social disapproval. We show that monetary incentives may backfire and reduce the performance of agents or their compliance with rules. In addition, these motives may generate very powerful incentives themselves.

Incentives, contracts, reciprocity, social approval, social norms, intrinsic motivation

Abstract:
Are initial competitive advantages self-reinforcing, so that markets exhibit an endogenous tendency to be dominated by only a few firms? Although this question is of great economic importance, no systematic empirical study has yet addressed it. Therefore, we examine experimentally whether firms with an initial cost advantage are more likely to invest in cost reductions than firms with higher initial costs. We find that the initial competitive advantages are indeed self-reinforcing, but subjects in the role of firms overinvest relative to the Nash equilibrium. However, the pattern of overinvestment even strengthens the tendency towards self-reinforcing cost advantages relative to the theoretical prediction. Further, as predicted by the Nash equilibrium, aggregate investment is not affected by the initial efficiency distribution. Finally, investment spillovers reduce investment,and investment is higher than the joint-profit maximizing benchmark for the case without spillovers and lower for the case with spillovers.

Cost-reducing Investment, Asymmetric Oligopoly, Increasing

Abstract:
The evidence suggests that relational contracting and legal rules play an important role in credit markets but on the basis of the prevailing field data it is difficult to pin down their causal impact. Here we show experimentally that relational incentives are a powerful causal determinant for the existence and performance of credit markets. In fact, in the absence of legal enforcement and reputation formation opportunities the credit market breaks down almost completely while if reputation formation is possible a stable credit market emerges even in the absence of legal enforcement of debt repayment. Introducing legal enforcement of repayments causes a further significant increase in credit market trading but has only a surprisingly small impact on overall efficiency. The reason is that legal enforcement of debt repayments weakens relational incentives and exacerbates another moral hazard problem in credit markets ﾖ the choice of inefficient high-risk projects.

credit markets, relationship lending, reputation formation, legal enforcement

Abstract:
Typically, laboratory experiments suffer from homogeneous subject pools and self-selection biases. The usefulness of survey data is limited by measurement error and by the questionability of their behavioural relevance. Here we present a method integrating interactive experiments and representative surveys thereby overcoming crucial weaknesses of both approaches. One of the major advantages of our approach is that it allows for the integration of experiments, which require interaction among the participants, with a survey of non-interacting respondents in a smooth and inexpensive way. We illustrate the power of our approach with the analysis of trust and trustworthiness in Germany by combining representative survey data with representative behavioural data from a social dilemma experiment. We identify which survey questions intended to elicit people's trust correlate well with behaviourally exhibited trust in the experiment. People above the age of 65, highly-skilled workers and people living in bigger households exhibit less trusting behaviour. Foreign citizens, Catholics and people favouring the Social Democratic Party or the Christian Democratic Party exhibit more trust. People above the age of 65 and those in good health behave more trustworthy or more altruistically, respectively. People below the age of 35, the unemployed and people who say they are in favour of none of the political parties behave less trustworthy or less altruistically, respectively.

Experiment, survey, trust, trustworthiness, altruism

Abstract:
Well-functioning groups enforce social norms that restrain opportunism, but the social structure of a society may encourage or inhibit norm enforcement. This paper studies how the exogenous assignment to different positions in an extreme social hierarchy - the caste system - affects individuals' willingness to punish violations of a cooperation norm. Although the analysis controls for individual wealth, education, and political participation, low-caste individuals exhibit a much lower willingness to punish norm violations that hurt members of their own caste, suggesting a cultural difference across caste status in the concern for members of one's own community. The lower willingness to punish may inhibit the low caste's ability to sustain collective action and so may contribute to its economic vulnerability.

Gender and Social Development, Corruption & Anitcorruption Law, Anthropology, Access to Finance, Social Inclusion & Institutions

Abstract:
In a recent paper, Hart and Moore (2008) introduce new behavioral assumptions that can explain long term contracts and important aspects of the employment relation. However, so far there exists no direct evidence that supports these assumptions and, in particular, Hart and Moore's notion that contracts provide reference points. In this paper, we examine experimentally the behavioral forces stipulated in their theory. The evidence confirms the model's prediction that there is a trade-off between rigidity and flexibility in a trading environment with incomplete contracts and ex ante uncertainty about the state of nature. Flexible contracts - which would dominate rigid contracts under standard assumptions - cause a significant amount of shading on ex post performance while under rigid contracts much less shading occurs. Thus, although rigid contracts rule out trading in some states of the world, parties frequently implement them. While our results are broadly consistent with established behavioral concepts, they cannot easily be explained by existing theories. The experiment appears to reveal a new behavioral force: ex ante competition legitimizes the terms of a contract, and aggrievement and shading occur mainly about outcomes within the contract.

Contracts, Reference Points, Experiment

Abstract:
When unemployment prevails, relations with a particular firm are valuable for workers. As a consequence, a worker may adhere to an implicit agreement to provide high effort, even when performance is not third-party enforceable. But can implicit agreements - or relational contracts - also motivate high worker performance when the labor market is tight? We examine this question by implementing an experimental market in which there is an excess demand for labor and the performance of workers is not third-party enforceable. We show that relational contracts emerge in which firms reward performing workers with wages that exceed the going market rate. This motivates workers to provide high effort, even though they could shirk and switch firms. Our results thus suggest that unemployment is not a necessary device to motivate workers. We also discuss how market conditions affect relational contracting by comparing identical labor markets with excess supply and excess demand for labor. Long-term relationships turn out to be less frequent when there is excess demand for labor compared to a market characterized by unemployment. Surprisingly though, this does not compromise market performance.

relational contracts, involuntary unemployment

Abstract:
Engelmann and Strobel (AER 2004) question the relevance of inequity aversion in simple dictator game experiments claiming that a combination of a preference for efficiency and a Rawlsian motive for helping the least well-off is more important than inequity aversion. We show that these results are partly based on a strong subject pool effect. The participants of the E&S experiments were undergraduate students of economics and business administration who self-selected into their field of study (economics) and learned in the first semester that efficiency is desirable. We show that for non-economists the preference for efficiency is much less pronounced. We also find a non-negligible gender effect indicating that women are more egalitarian than men. However, perhaps surprisingly, the dominance of equality over efficiency is unrelated to political attitudes.

Social preferences, inequity aversion, preferences for efficiency

Abstract:
This paper discusses recent neuroeconomic evidence related to other-regarding behaviors and the decision to trust in other people's other-regarding behavior. This evidence supports the view that people derive non-pecuniary utility (i) from mutual cooperation in social dilemma (SD) games and (ii) from punishing unfair behavior. Thus, mutual cooperation and the punishment of free riders in SD games is not irrational, but better understood as rational behavior of people with corresponding social preferences. We also report the results of a recent study that examines the impact of the neuropeptide Oxytocin (OT) on trusting and trustworthy behavior in a sequential SD. Animal studies have identified Oxytocin as a hormone that induces pro-social approach behavior, suggesting that it may also affect pro-social behavior in humans. Indeed, the study shows that subjects given Oxytocin exhibit much more trusting behavior, suggesting that OT has a direct impact on certain aspects of subjects' social preferences. Interestingly, however, although Oxytocin affects trusting behavior, it has no effect on subjects' trustworthiness.

Neuroconomic, social preferences, foundation of trust

Abstract:
This paper reports on a two-task principal-agent experiment in which only one task is contractible. The principal can either offer a piece-rate contract or a (voluntary) bonus to the agent. Bonus contracts strongly outperform piece-rate contracts. Many principals reward high effort on both tasks with substantial bonuses. Agents anticipate this and provide high effort on both tasks. In contrast, almost all agents with a piece-rate contract focus on the first task and disregard the second. Principals understand this and predominantly offer bonus contracts. This behavior contradicts the self-interest theory but is consistent with theories of fairness.

Abstract:
In recent years a large number of experimental studies have documented the existence of strong reciprocity among humans. Strong reciprocity means that people willingly repay gifts and punish the violation of cooperation and fairness norms even in anonymous one-shot encounters with genetically unrelated strangers. We provide ethnographic and experimental evidence suggesting that ultimate theories of kin selection, reciprocal altruism, costly signaling and indirect reciprocity do not provide satisfactory evolutionary explanations of strong reciprocity. The problem of these theories is that they can rationalize strong reciprocity only if it is viewed as maladaptive behaviour whereas the evidence suggests that it is an adaptive trait. Thus, we conclude that alternative evolutionary approaches are needed to provide ultimate accounts of strong reciprocity.

Reciprocity, maladaption, evolutionary foundations, human altruism

Abstract:
Well-functioning groups enforce social norms that restrain opportunism, but the social structure of a society may encourage or inhibit norm enforcement. Here we study how the exogenous assignment to different positions in an extreme social hierarchy - the caste system - affects individuals' willingness to punish violations of a cooperation norm. Although we control for individual wealth, education, and political participation, low caste individuals exhibit a much lower willingness to punish norm violations that hurt members of their own caste, suggesting a cultural difference across caste status in the concern for members of one's own community. The lower willingness to punish may inhibit the low caste's ability to sustain collective action and so may contribute to its economic vulnerability.

social norms, informal sanctions, third party punishment, endogenous social preferences, social exclusion, collective action, caste

Abstract:
In a recent paper, Hart and Moore (2008) introduce new behavioral assumptions that can explain long-term contracts and important aspects of the employment relation. However, so far there exists no direct evidence that supports these assumptions and, in particular, Hart and Moore's notion that contracts provide reference points. In this paper, we examine experimentally the behavioral forces stipulated in their theory. The evidence confirms the model's prediction that there is a tradeoff between rigidity and flexibility in a trading environment with incomplete contracts and ex ante uncertainty about the state of nature. Flexible contracts - which would dominate rigid contracts under standard assumptions - cause a significant amount of shading on ex post performance, while under rigid contracts, much less shading occurs. Thus, although rigid contracts rule out trading in some states of the world, parties frequently implement them. While our results are broadly consistent with established behavioral concepts, they cannot easily be explained by existing theories. The experiment appears to reveal a new behavioral force: ex ante competition legitimizes the terms of a contract, and aggrievement and shading occur mainly about outcomes within the contract.

Abstract:
No abstract available.

Abstract:
This Paper reports on a two-task principal-agent experiment in which only one task is contractible. The principal can either offer a piece-rate contract or a (voluntary) bonus to the agent. Bonus contracts strongly outperform piece rate contracts. Many principals reward high efforts on both tasks with substantial bonuses. Agents anticipate this and provide high efforts on both tasks. In contrast, almost all agents with a piece-rate contract focus on the first task and disregard the second. Principals understand this and predominantly offer bonus contracts. This behavior contradicts the self-interest theory but is consistent with theories of fairness.

Incentives, moral hazard, multiple tasks, fairness, experiments

Abstract:
We study the impact of reputational incentives in markets characterised by moral hazard problems. Social preferences have been shown to enhance contract enforcement in these markets, while at the same time generating considerable wage and price rigidity. Reputation powerfully amplifies the positive effects of social preferences on contract enforcement by increasing contract efficiency substantially. This effect is, however, associated with a considerable bilateralisation of market interactions, suggesting that it may aggravate price rigidities. Surprisingly, reputation in fact weakens the wage and price rigidities arising from social preferences. Thus, in markets characterised by moral hazard, reputational incentives unambiguously increase mutually beneficial exchanges, reduce rents, and render markets more responsive to supply and demand shocks.

Abstract:
In this paper we reply to Binmore and Shaked's criticism of the Fehr-Schmidt model of inequity aversion. We put the theory and their arguments into perspective and show that their criticism is not substantiated. Finally, we briefly comment on the main challenges for future research on social preferences.

Experiments, other-regarding preferences, inequity aversion

Abstract:
We report on several experiments on the optimal allocation of ownership rights. The experiments confirm the property rights approach by showing that the ownership structure affects relationship-specific investments and that subjects attain the most efficient ownership allocation despite starting from different initial conditions. However, in contrast to the property rights approach, the most efficient ownership structure is joint ownership. These results cannot be explained by the self-interest model nor by models that assume that all people behave fairly but they are largely consistent with approaches that focus on the interaction between selfish and fair players.

Abstract:
Since Durkheim, sociological explanations of social cooperation have emphasized the internalization of values that induce norm compliance. Since Adam Smith, economic explanations of social cooperation have emphasized incentives that induce selfish individuals to cooperate. Here, we develop a general approach¿the Beliefs, Preferences, and Constraints approach - showing that each of the above models is a special case. Our approach is based on evidence indicating that pure Homo Sociologicus and pure Homo Economicus views are wrong. We show that self-regarding and norm-regarding actors coexist and that the available action opportunities determine which of these actor types dominates the aggregate level of social cooperation. Our approach contributes to the solution of long-standing problems, including the problems of social order and collective action, the determinants and consequences of social exchanges, the microfoundations of emergent aggregate patterns of social interactions, and the measurement of the impact of cultural and economic practices on individuals' social goals.

social order, social exchange, cooperation, punishment, strong reciprocity

Abstract:
Trust pervades human societies. Trust is indispensable in friendship, love, families and organizations, and plays a key role in economic exchange and politics. In the absence of trust among trading partners, market transactions break down. In the absence of trust in a country's institutions and leaders, political legitimacy breaks down. Much recent evidence indicates that trust contributes to economic, political and social success. Little is known, however, about the biological basis of trust among humans. Here we show that intranasal administration of oxytocin, a neuropeptide that plays a key role in social attachment and affiliation in non-human mammals, causes a substantial increase in trust among humans, thereby greatly increasing the benefits from social interactions. We also show that the effect of oxytocin on trust is not due to a general increase in the readiness to bear risks. On the contrary, oxytocin specifically affects an individual's willingness to accept social risks arising through interpersonal interactions. These results concur with animal research suggesting an essential role for oxytocin as a biological basis of prosocial approach behaviour.

Trust, oxytocin, prosocial behavior

Abstract:
We examine the characteristics and the relative strength of third party sanctions in a series of experiments. We hypothesize that egalitarian distribution norms and cooperation norms apply in our experiments, and that third parties, whose economic payoff is unaffected by the norm violation, may be willing to enforce these norms although the enforcement is costly for them. Almost two-thirds of the third parties indeed punish the violation of the distribution norm and their punishment increases the more the norm is violated. Likewise, up to roughly 60 percent of the third parties punish the violation of the cooperation norm. Thus, our results show that the notion of strong reciprocity also extends to the sanctioning behavior of "unaffected" third parties. In addition, these experiments suggest that third party punishment games are powerful tools for studying the characteristics and the content of social norms. Further experiments indicate that second parties, who's economic payoff is reduced by the norm violation, punish the violation much more strongly than do third parties. We also collect questionnaire evidence that is consistent with the view that fairness motives and negative emotions are a determinant of third party sanctions.

Social norm, sanction, punishment, strong reciprocity, social preference, third party

Abstract:
Money illusion means that people behave differently when the same objective situation is represented in nominal terms rather than in real terms. This paper shows that seemingly innocuous differences in payoff representation cause pronounced differences in nominal price inertia indicating the behavioral importance of money illusion. In particular, if the payoff information is presented to subjects in nominal terms, price expectations and actual price choices after a fully anticipated negative nominal shock are much stickier than when payoff information is presented in real terms. In addition we show that money illusion causes asymmetric effects of negative and positive nominal shocks. While nominal inertia is quite substantial and long-lasting after a negative shock, it is rather small after a positive shock.

Money Illusion, Nominal Inertia, Sticky Prices, Non-neutrality of Money

Abstract:
This paper presents an experimental examination of the Falkinger (1996) mechanism for overcoming the free-rider problem. The basic idea of the mechanism is that deviations from the mean contribution to the public good are taxed and subsidized. The mechanism has attractive properties because (i) it induces higher contributions to the public good and can implement an efficient level of contributions as a Nash equilibrium, (ii) the government budget is always balanced irrespective of the level of individual contributions, (iii) it is simple and policy makers need only little information to implement the mechanism.

To examine the empirical properties of the mechanism we conducted a large series of experiments. It turns out that the introduction of the mechanism generates immediate and large efficiency gains. This result is robust throughout many different experimental settings. Moreover, in the presence of the mechanism the Nash equilibrium is a rather good predictor of behavior.

Abstract:
Do employers and workers underbid prevailing wages if there is unemployment? Do employers take advantage of workers' underbidding by lowering wages? We hypothesize that under conditions of incomplete labor contracts, wage levels may positively affect workers' propensity to cooperate. This, in turn, may prevent firms from underbidding or accepting the underbidding of workers. Experimental double auctions conducted for the purpose of examining these hypotheses yield the following results: (i) Workers' underbidding is very frequent, but employers refuse to accept workers' low wage offers in markets with incomplete labor contracts. However, in the presence of complete labor contracts, employers accept and actively enforce wages close to the competitive level. (ii) Workers' effort is positively related to the wage level. Therefore, wage cutting is costly for the employer if workers have discretion over their effort level. This holds true even in the presence of explicit performance incentives.