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Concept: Dictator game


The strong reciprocity model of the evolution of human cooperation has gained some acceptance, partly on the basis of support from experimental findings. The observation that unfair offers in the ultimatum game are frequently rejected constitutes an important piece of the experimental evidence for strong reciprocity. In the present study, we have challenged the idea that the rejection response in the ultimatum game provides evidence of the assumption held by strong reciprocity theorists that negative reciprocity observed in the ultimatum game is inseparably related to positive reciprocity as the two sides of a preference for fairness. The prediction of an inseparable relationship between positive and negative reciprocity was rejected on the basis of the results of a series of experiments that we conducted using the ultimatum game, the dictator game, the trust game, and the prisoner’s dilemma game. We did not find any correlation between the participants' tendencies to reject unfair offers in the ultimatum game and their tendencies to exhibit various prosocial behaviors in the other games, including their inclinations to positively reciprocate in the trust game. The participants' responses to postexperimental questions add support to the view that the rejection of unfair offers in the ultimatum game is a tacit strategy for avoiding the imposition of an inferior status.

Concepts: Game theory, Hypothesis, The Evolution of Cooperation, Prisoner's dilemma, Dictator game, Ultimatum game, Experimental economics, Reciprocity


We exploit the fact that generosity and trustworthiness are highly correlated and the former can thus be a sign of the latter. Subjects decide between a generous and a mean split in a dictator game. Some of them are informed from the start that afterwards they will participate in a trust game and that their choice in the dictator game may matter; others are not informed in advance. In the trust game, before trusters decide whether or not to trust, some trustees can reveal (or conceal) only their true choice in the dictator game, while others can say to trusters, truthfully or otherwise, what they chose. We find that a generous choice made naturally by uninformed trustees and reliably revealed is more effective in persuading trusters to trust than a generous choice that could be strategic or a lie. Moreover, we find that, when they can, mean subjects lie and go on to be untrustworthy.

Concepts: Game theory, Virtue, Social psychology, Dictator game, Ultimatum game


Psychopathic personality traits are linked with selfish and non-cooperative responses during economical decision making games. However, the possibility that these responses may vary when responding to members of the in-group and the out-group has not yet been explored. We aimed to examine the effects of primary (selfish, uncaring) and secondary (impulsive, irresponsible) psychopathic personality traits on the responses of non-offending participants to the in-group and the out-group (defined in terms of affiliation to a UK University) across a series of economical decision making games. We asked a total of 60 participants to act as the proposer in both the dictator game and the ultimatum game. We found that across both tasks, those who scored highly for secondary psychopathic traits showed an elevated intergroup bias, making more generous offers toward members of the in-group relative to the out-group. An exaggerated intergroup bias may therefore represent a motivational factor for the antisocial behavior of those with elevated secondary psychopathic traits.

Concepts: Game theory, Abnormal psychology, Antisocial personality disorder, Conduct disorder, Psychopathy, Dictator game, Personality disorders, Narcissism


The design of effective donor recruitment campaigns requires an accurate understanding of donor motivations. This requires cross-validation of theoretically derived, psychometrically assessed motivations with behavioural preferences. Theoretical models suggest that blood donors should be more sensitive than nondonors to violations of fairness norms. Specifically, active blood donors, compared to nondonors, should endorse beliefs of reciprocal fairness, norms of both positive and negative reciprocity and reject more unfair offers in a behavioural economic game (the ultimatum game). This study is the first to test this hypothesis.

Concepts: Game theory, Economics, Assessment, Psychometrics, Motivation, Dictator game, Reciprocity, Subgame perfect equilibrium


Social decision making has recently been evaluated in alcohol use disorder (AUD) using the ultimatum game (UG) task, suggesting a possible deficit in aversive emotion regulation elicited by the unfairness during this task. Despite the relevance to relapse of this possible faulty regulation, the brain correlates of the UG in AUD are unknown.

Concepts: Game theory, Psychology, Critical thinking, Cognition, Decision theory, Dictator game, Rulemaking, Subgame perfect equilibrium


In this research we examine the phenomenon of egocentric reciprocity, where individuals protect self-interest by adopting an eye-for-an-eye strategy in negatively imbalanced exchanges, and by taking advantage of overly generous treatment in positively imbalanced exchanges. We conducted two experiments using a modified ultimatum game examining attitudinal and behavioral responses to imbalanced exchanges. The experiments allowed us to explore the moderating role of relational closeness (i.e., whether the game partner was a friend or a stranger) and the mediating role of anger and indebtedness in these moderated relationships. Our results consistently demonstrate the phenomenon of egocentric reciprocity. Most importantly, this research reveals that friendship places a boundary on this egocentric tendency, and that the effects may partially be explained by anger experienced in response to exchange.

Concepts: Game theory, Sociology, Interpersonal relationship, Dictator game, Mediation, Friendship, Exchange, Subgame perfect equilibrium


This study examined reward-related decision-making in children and adolescents with ADHD in a social context, using economic games. We furthermore examined the role of individual differences in reward-related decision-making, specifically, the roles of reward sensitivity and prosocial skills. Children and adolescents (9-17 years) with ADHD-combined subtype (n = 29; 20 boys) and healthy controls (n = 38; 20 boys) completed the ultimatum game and dictator game as measures of reward-related decision-making in social contexts. Prosocial skills were measured with the Interpersonal Reactivity Index. The ADHD group had a larger discrepancy between ultimatum game and dictator game offers than controls, indicating strategic rather than fairness driven decisions. This finding was supported by self-reports showing fewer individuals with ADHD than controls who considered fairness as motive for the decisions. Perspective taking or empathic concern did not differ between groups and was not significantly associated with offers. In conclusion, the results suggest that rather than a failure to understand the perspective of others, children and adolescents with ADHD were less motivated by fairness than controls in simple social situations. Results encourage the use of economic games in ADHD research.

Concepts: Game theory, Decision making, Sensitivity and specificity, Social psychology, Dictator game, Ultimatum game, Experimental economics, Subgame perfect equilibrium


Trustful and trustworthy behaviors have important externalities for the society. But what exactly drives people to behave in a trustful and trustworthy manner? Building on research suggesting that individuals' social preferences might be a common factor informing both behaviors, we study the impact of a set of different motives on individuals' choices in a dual-role Trust Game (TG). We employ data from a large-scale representative experiment (N = 774), where all subjects played both roles of a binary TG with real monetary incentives. Subjects' social motives were inferred using their decisions in a Dictator Game and a dual-role Ultimatum Game. Next to self-interest and strategic motives we consider preferences for altruism, spitefulness, egalitarianism, and efficiency. We demonstrate that there exists considerable heterogeneity in motives in the TG. Most importantly, among individuals who choose to trust as trustors, social motives can differ dramatically as there is a non-negligible proportion of them who seem to act out of (strategic) self-interest whereas others are driven more by efficiency considerations. Subjects' elicited trustworthiness, however, can be used to infer such motivations: while the former are not trustworthy as trustees, the latter are. We discuss that research on trust can benefit from adding the second player’s choice in TG designs.

Concepts: Game theory, Motivation, Choice, Dictator game, Ultimatum game, Experimental economics, Trustworthiness, Inequity aversion


Social comparison is a prerequisite for processing fairness, although the two types of cognition may be associated with different emotions. Whereas social comparison may induce envy, the perception of unfairness may elicit anger. Yet, it remains unclear whether people who tend to have a strong sense of fairness also tend to compare themselves more with others. Here, Study 1 used a modified ultimatum game (UG) and a social comparison game (SCG) to examine the relationship between justice sensitivity and social comparison sensitivity in 51 young adults. Study 2 examined self-reported social comparison and justice sensitivity in 142 young adults. Both studies showed a positive correlation between social comparison sensitivity and justice sensitivity. We reason that social comparison and justice sensitivity have an important positive correlation in human decision-making. The rejection of self-disadvantageous inequality offers may be due to the social comparison effect, which suggests that the tendency to compare oneself with others may contribute to having a strong sense of justice. Our findings suggest that the predictions of game theory may vary depending on the social culture context and incorporating notions of fairness and social comparison tendency may be essential to better predict the actual behavior of players in social interactive situations.

Concepts: Game theory, Psychology, Cognition, Perception, Sense, Dictator game, Ultimatum game, Subgame perfect equilibrium


Inequality aversion is a typical form of fairness preferences, which can explain the behaviors in many social exchange situations such as the ultimatum game (UG). There are two kinds of inequality aversion-disadvantageous inequality aversion of responders and advantageous inequality aversion of proposers in the ultimatum game. Although neuroscience research has reported neural correlates of disadvantageous inequality aversion, there are still debates about advantageous inequality aversion of proposers. In this paper, we developed a variant of ultimatum game in which participants played the UG as proposers. On each trial, first, the offer was randomly presented, then, participants as proposers decided whether to choose this offer; next, responders decided whether to accept or not. Offers that responders got 1-20% of the pie are defined as advantageous unfair offers of proposers, whereas offers that responders got 31-50% are defined as fair offers. Event-related brain potentials recorded from the participants showed that more negative-going medial frontal negativity (MFN) was elicited by advantageous unfair offers compared to fair offers in the early time window (250-350ms), which suggested that proposers were averse to advantageous inequality.

Concepts: Game theory, Neuroscience, Event-related potential, Dictator game, Ultimatum game, Experimental economics, Subgame perfect equilibrium, Inequity aversion