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Abstract:
This Paper presents a formal theory of reciprocity. Reciprocity means that people reward kind actions and punish unkind ones. The theory takes into account that people evaluate the kindness of an action not only by its consequences but also by the intention underlying this action. The theory explains the relevant stylized facts of a wide range of experimental games. Among them are the ultimatum game, the gift-exchange game, a reduced best-shot game, the dictator game, the prisoner's dilemma, and public goods games. Furthermore, the theory explains why the same consequences trigger different reciprocal responses in different environments. Finally, the theory explains why in bilateral interactions outcomes tend to be 'fair' whereas in competitive markets even extremely unfair distributions may arise.

Reciprocity, fairness, cooperation, game theory

Abstract:
This paper presents a formal theory of reciprocity. Reciprocity means that people reward kind actions and punish unkind ones. The theory takes into account that people evaluate the kindness of an action not only by its consequences but also by the intention underlying this action. The theory explains the relevant stylized facts of a wide range of experimental games. Among them are the ultimatum game, the gift-exchange game, a reduced best-shot game, the dictator game, the prisoner's dilemma, and public goods games. Furthermore, the theory explains why the same consequences trigger different reciprocal responses in different environments Finally the theory explains why in bilaterial interactions outcomes tend to be "fair" whereas in competitive markets even extremely unfair distributions may arise.

Reciprocity, Fairness, Cooperation, Competition, Game Theory

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:
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:
The paper investigates the effect of interest policy on price bubbles, trading behavior and portfolio choice in experimental stock markets. A series of experiments has 8 participants trade an asset over 15 periods. Alternatively, the participants can invest money in interest-bearing bonds. Treatment groups are subjected to an endogenous interest policy, while control groups experience a constant interest rate. Our stock markets are characterized by bubbles. While we observe a small positive impact of our interest policy on bubbles, the policy also strongly increases market volatility. On the other hand, concerning portfolio choice, we find evidence for value-driven (rational) investment behavior.

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:
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:
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:
To fully understand the motives for delegating a decision right, it is important to study responsibility attributions for outcomes of delegated decisions. We conducted an experiment in which subjects were able to delegate the choice between a fair or unfair allocation, and used a punishment option to elicit responsibility attributions. Our results show that, first, responsibility attribution can be effectively shifted and, second, this constitutes a powerful motive for the delegation of a decision right. Furthermore, we propose a formal measure of responsibility and show that this measure outperforms measures based on outcome or intention in predicting punishment behavior.

delegation, decision rights, moral responsibility, blame shifting

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 z-Tree program was developed at the University of Zurich. It was specially designed to enable the conducting of economic experiments without much prior experience. It consists, on the one hand, of z-Tree, the ?Zurich Toolbox for Readymade Experiments?, and, on the other hand, of z-Leaf, the program used by the subjects. In z-Tree, one can define and conduct experiments. One can program a broad range of experiments with z-Tree, including public goods games, structured bargaining experiments, posted-offer-markets or double auctions. The programming of z-Tree requires a certain experience. Thereafter, the effort required for conducting experiments is minimal: An experimenter with a certain amount of experience can program a public goods game in an hour and a double auction in less than a day.

Abstract:
We provide a direct test of the role of social preferences in voluntary cooperation. We elicit individuals' cooperation preference in one experiment and make a point prediction about the contribution to a repeated public good. This allows for a novel test as to whether there are types of players who behave consistently with their elicited preferences. We find clear-cut evidence for the existence of types. People who express free rider preferences show the most systematic deviation from the predicted contributions, because they contribute in the first half of the experiment. We also show that the interaction of heterogeneous types explains a large part of the dynamics of free riding.

Public goods games, experiments, voluntary contributions, conditional cooperation, free riding

Abstract:
Field evidence suggests that people belonging to the same group often behave similarly, i.e., behaviour exhibits social interaction effects. We conduct an experiment that avoids the identification problem present in the field. Our novel design feature is that each subject simultaneously is a member of two randomly assigned and identical groups where only members ("neighbours") are different. In both groups subjects contribute to a public good. We speak of social interactions if the same subject at the same time makes group-specific contributions that depend on their respective neighbours' contribution. We find that a majority of subjects exhibits social interaction effects.

Social Interactions, Identification, Experiments

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:
"Winner-Take-All"-markets, i.e. markets in which the relative and not the absolute performance is decisive, have gained in importance. Such markets have a tendency to provoke inefficiently many entries. We investigate the functioning of such markets with the help of experiments and show that there are even more inefficient entries than predicted by the Nash equilibrium. Moreover, this effect increases with group size. Quantal response equilibrium predicts the increase in group size but fails to predict the excess entry in the smaller group. We show that the excess entry is not caused by coordination failures. Furthermore, individual entry behavior is not significantly linked to risk preferences. We discuss several concepts that might explain the observed excess entry.

Winner-take-all market, Excess entry, Experiment, Market entry

Abstract:
We study indirect reciprocity and strategic reputation building in an experimental helping game. At any time only half of the subjects can build a reputation. This allows us to study both pure indirect reciprocity that is not contaminated by strategic reputation building and the impact of incentives for strategic reputation building on the helping rate. We find that while pure indirect reciprocity appears to be important, the helping choice seems to be influenced at least as much by strategic considerations. Strategic do better than non-strategic players and non-reciprocal do better than reciprocal players, casting doubt on previously proposed evolutionary explanations for indirect reciprocity.

Abstract:
We provide a test of the role of social preferences and beliefs in voluntary cooperation and its decline. We elicit individuals' cooperation preferences in one experiment and use them - as well as subjects' elicited beliefs - to explain contributions to a public good played repeatedly. We find substantial heterogeneity in people's preferences. With simulation methods based on this data, we show that the decline of cooperation can be driven by the fact that most people have a preference to contribute less than others, rather than by their changing beliefs of others' contribution over time. Universal free riding is very likely despite the fact that most people are not selfish.

public goods experiments, social preferences, conditional cooperation, free riding

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:
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:
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:
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