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Sense of agency (SoA) describes the feeling of control over one's actions and their consequences. One proposed index of implicit SoA is temporal compression, which refers to the phenomenon that voluntary actions and their outcomes are perceived as closer in time than they actually are. The present study measured temporal compression in the social norm violation situation. In two experiments participants joined in an Ultimatum game (UG), in which they were presented with offers that varied in fairness and they could choose to accept or reject the offers by pressing buttons. A neutral sound would occur after their choices in the UG and the participants had to estimate the time interval between their button pressing and the occurrence of the sound, and EEG signals were recorded during the task. Experiment 1 demonstrated that rejecting unfair offers decreased the perceived interval between action and outcome compared to accepting fair offers, suggesting a higher level of SoA after rejecting unfair offers. Experiment 2 replicated these results and further revealed an attenuated N1 in response to the sound following rejections of unfairness. Taken together, these results highlight the importance of social norms in affecting people's behaviors and agency experiences. [ABSTRACT FROM AUTHOR]

AI is now an integral part of everyday decision-making, assisting us in both routine and high-stakes choices. These AI models often learn from human behavior, assuming this training data is unbiased. However, we report five studies that show that people change their behavior to instill desired routines into AI, indicating this assumption is invalid. To show this behavioral shift, we recruited participants to play the ultimatum game, where they were asked to decide whether to accept proposals of monetary splits made by either other human participants or AI. Some participants were informed their choices would be used to train an AI proposer, while others did not receive this information. Across five experiments, we found that people modified their behavior to train AI to make fair proposals, regardless of whether they could directly benefit from the AI training. After completing this task once, participants were invited to complete this task again but were told their responses would not be used for AI training. People who had previously trained AI persisted with this behavioral shift, indicating that the new behavioral routine had become habitual. This work demonstrates that using human behavior as training data has more consequences than previously thought since it can engender AI to perpetuate human biases and cause people to form habits that deviate from how they would normally act. Therefore, this work underscores a problem for AI algorithms that aim to learn unbiased representations of human preferences. [ABSTRACT FROM AUTHOR]

To better understand the individual differences in fairness, we used event-related potentials (ERPs) to explore the fairness characteristics of deaf college students through the ultimatum game task. Behaviorally, the significant main effect of the proposal type was found, which meant both deaf and hearing college students showed a lower acceptance rate for the more unfair proposal. Interestingly, we found a significant interaction between group and proposal type in the early stage (N1). Moreover, in the deaf college group, N1 (induced by moderately and very unfair proposals) was significantly larger than that of fair proposals. However, we found that deaf college students had smaller amplitudes on P2 and P3 than hearing college students. These results suggested that deaf college students might pursue more equity strongly so they are more sensitive to unfair information in the early stage. In a word, we should provide more fair allocations for deaf college students in our harmonious society. [ABSTRACT FROM AUTHOR]

The mini-Ultimatum Game (mini-UG) is a bargaining game used to assess the reactions of a responder to unfair offers made by a proposer under different intentionality conditions. Previous studies employing this task showed the activation of responders' right temporoparietal junction (rTPJ), which could be related to its involvement in judgments of intentionality. To verify this hypothesis, in the present study we applied online transcranial magnetic stimulation (TMS) over the rTPJ in responders during the mini-UG, in which we manipulated intention attribution implicitly. A cover story was employed to induce participants to believe they were interacting with another agent. We expected that interfering with the rTPJ could affect the ability of responders to assume proposers' perspective, producing higher rates of rejections of unfair offers when offers are perceived as independent from responders' intentionality to inequality. Twenty-six healthy women voluntarily participated in the study. In the mini-UG, an unfair distribution of the proposer (8/2 offer) was pitted against one of three alternative offers: fair-alternative (5/5), no-alternative (8/2), hyperfair-alternative (2/8). During the task, a train of TMS pulses was delivered at proposers' offer presentation in blocks of active (rTPJ) or control (Vertex) stimulation according to an ABAB design. As expected, findings showed that rejection of the no-alternative offers was higher under TMS stimulation of the rTPJ compared with the control TMS. This effect was modulated by the degree of trustworthiness in the cover story. These data contribute defining the mechanisms and brain areas underpinning social decision making as assessed by bargaining tasks. [ABSTRACT FROM AUTHOR]

In risky contexts, autism spectrum disorder (ASD) individuals exhibit more logical consistency and non-emotional decisions than do typical adults (TAs). This way of deciding could be also prevailing in social contexts, leading to maladaptive decisions. This evidence is scarce and inconsistent, and further research is needed. Recent developments in computational modeling allow analysis of decisional subcomponents that could provide valuable information to understand the decision-making and help address inconsistencies. Twenty-seven individuals with ASD and 25 TAs were submitted to a framing-task and the ultimatum game (UG). The Rescorla–Wagner computational model was used to analyze UG decisions. Results showed that in the UG, the ASD group exhibited a higher utilitarianism, characterized by lower aversion to unfairness and higher acceptance of offers. Moreover, this way of deciding was predicted by the higher economic rationality found in the framing task, where people with ASD did not manifest emotional biases such as framing effect. These results could suggest an atypical decision making, highly logical and non-emotional, as a robust feature of ASD. [ABSTRACT FROM AUTHOR]

Abstract Sense of agency (SoA) describes the feeling of control over one’s actions and their consequences. One proposed index of implicit SoA is temporal compression, which refers to the phenomenon that voluntary actions and their outcomes are perceived as closer in time than they actually are. The present study measured temporal compression in the social norm violation situation. In two experiments participants joined in an Ultimatum game (UG), in which they were presented with offers that varied in fairness and they could choose to accept or reject the offers by pressing buttons. A neutral sound would occur after their choices in the UG and the participants had to estimate the time interval between their button pressing and the occurrence of the sound, and EEG signals were recorded during the task. Experiment 1 demonstrated that rejecting unfair offers decreased the perceived interval between action and outcome compared to accepting fair offers, suggesting a higher level of SoA after rejecting unfair offers. Experiment 2 replicated these results and further revealed an attenuated N1 in response to the sound following rejections of unfairness. Taken together, these results highlight the importance of social norms in affecting people’s behaviors and agency experiences.

Although the attractiveness of voices plays an important role in social interactions, it is unclear how voice attractiveness and social interest influence social decision‐making. Here, we combined the ultimatum game with recording event‐related brain potentials (ERPs) and examined the effect of attractive versus unattractive voices of the proposers, expressing positive versus negative social interest ("I like you" vs. "I don't like you"), on the acceptance of the proposal. Overall, fair offers were accepted at significantly higher rates than unfair offers, and high voice attractiveness increased acceptance rates for all proposals. In ERPs in response to the voices, their attractiveness and expressed social interests yielded early additive effects in the N1 component, followed by interactions in the subsequent P2, P3 and N400 components. More importantly, unfair offers elicited a larger Medial Frontal Negativity (MFN) than fair offers but only when the proposer's voice was unattractive or when the voice carried positive social interest. These results suggest that both voice attractiveness and social interest moderate social decision‐making and there is a similar "beauty premium" for voices as for faces. [ABSTRACT FROM AUTHOR]

This paper analyzes fairness and bargaining in a dynamic bilateral matching market. Traders from both sides of the market are pairwise matched to share the gains from trade. The bargaining outcome depends on the traders' fairness attitudes. In equilibrium fairness matters because of market frictions. But, when these frictions become negligible, the equilibrium approaches the Walrasian competitive equilibrium, independently of the traders' inequity aversion. Fairness may yield a Pareto improvement; but also the contrary is possible. Overall, the market implications of fairness are very different from its effects in isolated bilateral bargaining. [ABSTRACT FROM AUTHOR]

Prior studies in Social Neuroeconomics have consistently reported activation in social cognition regions during interactive economic games, suggesting mentalizing during economic choice. Such mentalizing occurs during active participation in the game, as well as during passive observation of others' interactions. We designed a novel version of the classic false-belief task (FBT) in which participants read vignettes about interactions between agents in the ultimatum and trust games and were subsequently asked to infer the agents' beliefs. We compared activation patterns during the economic games FBT to those during the classic FBT using conjunction analyses. We find significant overlap in the left temporoparietal junction (TPJ) and dorsal medial prefrontal cortex, as well as the temporal pole (TP) during two task phases: belief formation and belief inference. Moreover, generalized Psychophysiological Interaction (gPPI) analyses show that during belief formation, the right TPJ is a target of both the left TPJ and the right TP seed regions, whereas during belief inferences all seed regions show interconnectivity with each other. These results indicate that across different task types and phases, mentalizing is associated with activation and connectivity across central nodes of the social cognition network. Importantly, this is the case for both the novel economic games and the classic FBTs.

Third-party punishment (TPP) plays an irreplaceable role in maintaining social fairness. Punishment power is a significant area of study within economic games. However, the impact of whether or not the second-party possesses punishment power on TPP remains unexplored. The present study utilizes the high temporal resolution of EEG and time-frequency analysis, intra-barin functional connectivity analysis, inter-brain synchronization (IBS) analysis, and granger causality analysis(GCA) to comprehensively explore the neural mechanism of TPP from the perspective of third-party individual's decision-making and IBS in the real-time social interaction. Time-frequency results found that, the absence of the punishment power activated more theta-band and alpha-band power compare to when second-party has punishment power. When second-party has no punishment power, functional connection results observed stronger functional connectivity in theta band for medium unfair offers between rTPJ and PFC. Dual-brain analysis revealed that when the second-party has no punishment power, there is a significantly higher IBS in the alpha band between the frontal and frontal-central lobes of the second-party and the parietal and parietal occipital lobes of the third-party. GCA results further showed that the direction of IBS from third-party to second-party was significantly stronger than from second-party to third-party. This study demonstrates that the absence of the second-party's punishment power promote TPP, and similar cognitive process of thinking on how to maintain social fairness enhances IBS. The current study emphasizes the influence of punishment power on TPP, broadens the research perspective and contributes crucial insights into maintain social fairness.

Abstract Partner choice promotes competition among individuals to be selected as a cooperative partner, a phenomenon referred to as competitive altruism. We explored whether chimpanzees engage in competitive altruism in a triadic Ultimatum Game where two proposers can send offers simultaneously or consecutively to a responder who can only accept one of the two competing offers. In a dyadic control condition only one proposer at a time could send an offer to the responder. Chimpanzees increased their offers across trials in the competitive triadic, but not in the dyadic control condition. Chimpanzees also increased their offers after being rejected in previous triadic trials. Furthermore, we found that chimpanzees, under specific conditions, outcompete first proposers in triadic consecutive trials before the responder could choose which offer to accept by offering more than what is expected if they acted randomly or simply offered the smallest possible amount. These results suggest that competitive altruism in chimpanzees did not emerge just as a by-product of them trying to increase over previous losses. Chimpanzees might consider how others’ interactions affect their outcomes and engage in strategies to maximize their chances of being selected as cooperative partners.

We examined how induced cultural orientation (individualist or collectivist) influences decisions in resource distribution in middle childhood (N = 166, M age = 9.85, SD = 0.96, females = 51.5%), early adolescence (N = 254, M age = 13.42, SD = 0.72, females = 50.8%) and young adults (N = 338, M age = 21.41, SD = 3.77, females = 46.4%), among Costa Rican samples. We found influence of induced individualism in rejection of highly unfair offers in the ultimatum game (9:1) in the three age groups and to a lesser degree among adolescents compared to children and adults. [ABSTRACT FROM AUTHOR]

The ultimatum and dictator games were developed to help identify the fundamental motivators of human behavior, typically by asking participants to share windfall endowments with other persons. In the ultimatum game, a common observation is that proposers offer, and responders refuse to accept, a much larger share of the endowment than is predicted by rational choice theory. However, in the real world, windfalls are rare: money is usually earned. I report here a small study aimed at testing how participants react to an ultimatum game after they have earned their endowments by either building a Lego model or spending some time sorting out screws by their length. I find that the shares that proposers offer and responders accept are significantly lower than that typically observed with windfall money, an observation that is intensified when the task undertaken to earn the endowment is generally less enjoyable and thus perhaps more effortful (i.e., screw sorting compared to Lego building). I suggest, therefore, that considerations of effort-based desert are often important drivers behind individual decision-making, and that laboratory experiments, if intended to inform public policy design and implementation, ought to mirror the broad characteristics of the realities that people face. [ABSTRACT FROM AUTHOR]

The Ultimatum Game is a simplistic representation of bargaining processes occurring in social networks. In the standard version of this game, the first player, called the proposer, makes an offer on how to split a certain amount of money. If the second player, called the responder, accepts the offer, the money is divided according to the proposal; if the responder declines the offer, both players receive no money. In this article, an agent-based model is employed to evaluate the performance of five distinct strategies of playing a modified version of this game. A strategy corresponds to instructions on how a player must act as the proposer and as the responder. Here, the strategies are inspired by the following basic emotions: anger, fear, joy, sadness, and surprise. Thus, in the game, each interacting agent is a player endowed with one of these five basic emotions. In the modified version explored in this article, the spatial dimension is taken into account and the survival of the players depends on successful negotiations. Numerical simulations are performed in order to determine which basic emotion dominates the population in terms of prevalence and accumulated money. Information entropy is also computed to assess the time evolution of population diversity and money distribution. From the obtained results, a conjecture on the emergence of the sense of fairness is formulated. [ABSTRACT FROM AUTHOR]

Research from the last four decades suggests that fairness plays an important role in economic transactions. However, the vast majority of this research investigates behavior in an environment where agents are fully informed. We develop a new experimental paradigm—nesting the widely used ultimatum game—and find that fairness has less impact on outcomes when agents are less informed. As we remove information, offers become less generous and unfair offers are more likely to be accepted. [ABSTRACT FROM AUTHOR]

Introduction: Human decision-making pertaining to gains compared to those pertaining losses is shown to be quite different. However, mixed evidence is provided regarding the effect on the decision-makers' prosocial behaviors; that is, losses are shown to either increase or decrease prosocial behaviors. In this context, the effect of social norms on observed behavior can play a crucial role. Methods: To examine this aspect in more detail, we conducted incentivized ultimatum game experiments and analyzed data from three treatments, the control treatments (without specific norm focus), and two different norm-focus treatments (“average behavior” treatment and “self-interested behavior” treatment). In total, 550 participants took part in our experiment. Basically, we found no significant difference between the division of gains and losses in the “control” and “self-interested behavior” treatments. Results and discussion: However, we found such a difference in the “average behavior” treatment. In addition, we found that inducing a norm focus leads to less variance in proposers' behavior and a greater concentration of their demands around the induced norm in the “average behavior” treatment. In contrast, we found a higher variance in proposers' behavior in the “self-interested behavior” treatment. In terms of responders' behaviors, we observed a tendency toward a higher frequency of responders' rejections in the loss domain compared to the gains domain. [ABSTRACT FROM AUTHOR]

In resource-allocation situations, the allocators often make advantageous unfair allocations intentionally, which may threaten their moral self. We propose that allocators self-servingly interpret these allocations as less unfair, which potentially lessens threat to their moral self, allowing them allocate unfairly. In a hypothetical dictator game (Experiment 1, 3 and 4), a real dictator game (Experiment 2 and 5) and a hypothetical ultimatum game (Experiment 3), we compared the fairness perceptions of allocators with those of recipients (Experiment 1 and 2) and a control group (Experiment 3 and 4), both before (Experiment 1–4) and after (Experiment 5) the allocations. The studies consistently found that the allocators perceived the possible advantageous unfair allocations as less unfair, and these fairness perceptions further predicted their allocations. We highlight the psychological mechanism, specifically the self-serving bias in fairness perception that may lessen the anticipated threat to the allocators' moral self, allowing them to allocate unfairly. [ABSTRACT FROM AUTHOR]

Partner choice promotes competition among individuals to be selected as a cooperative partner, a phenomenon referred to as competitive altruism. We explored whether chimpanzees engage in competitive altruism in a triadic Ultimatum Game where two proposers can send offers simultaneously or consecutively to a responder who can only accept one of the two competing offers. In a dyadic control condition only one proposer at a time could send an offer to the responder. Chimpanzees increased their offers across trials in the competitive triadic, but not in the dyadic control condition. Chimpanzees also increased their offers after being rejected in previous triadic trials. Furthermore, we found that chimpanzees, under specific conditions, outcompete first proposers in triadic consecutive trials before the responder could choose which offer to accept by offering more than what is expected if they acted randomly or simply offered the smallest possible amount. These results suggest that competitive altruism in chimpanzees did not emerge just as a by-product of them trying to increase over previous losses. Chimpanzees might consider how others' interactions affect their outcomes and engage in strategies to maximize their chances of being selected as cooperative partners. [ABSTRACT FROM AUTHOR]

Stress is a crucial factor affecting social decision-making. However, its impacts on the behavioral and neural processes of females’ unfairness decision-making remain unclear. Combining computational modeling and functional near-infrared spectroscopy (fNIRS), this study attempted to illuminate the neurocomputational signature of unfairness decision-making in females. We also considered the effect of trait stress coping styles. Forty-four healthy young females (20.98 ± 2.89 years) were randomly assigned to the stress group (n = 21) and the control group (n = 23). Acute psychosocial stress was induced by the Trier Social Stress Test (TSST), and participants then completed the one-shot ultimatum game (UG) as responders. The results showed that acute psychosocial stress reduced the adaptability to fairness and lead to more random decision-making responses. Moreover, in the stress group, a high level of negative coping style predicted more deterministic decision. fNIRS results showed that stress led to an increase of oxy-hemoglobin (HbO) peak in the right temporoparietal junction (rTPJ), while decreased the activation of left middle temporal gyrus (lMTG) when presented the moderately unfair (MU) offers. This signified more involvement of the mentalization and the inhibition of moral processing. Moreover, individuals with higher negative coping scores showed more deterministic decision behaviors under stress. Taken together, our study emphasizes the role of acute psychosocial stress in affecting females’ unfairness decision-making mechanisms in social interactions, and provides evidences for the “tend and befriend” pattern based on a cognitive neuroscience perspective.

To better understand the individual differences in fairness, we used event-related potentials (ERPs) to explore the fairness characteristics of deaf college students through the ultimatum game task. Behaviorally, the significant main effect of the proposal type was found, which meant both deaf and hearing college students showed a lower acceptance rate for the more unfair proposal. Interestingly, we found a significant interaction between group and proposal type in the early stage (N1). Moreover, in the deaf college group, N1 (induced by moderately and very unfair proposals) was significantly larger than that of fair proposals. However, we found that deaf college students had smaller amplitudes on P2 and P3 than hearing college students. These results suggested that deaf college students might pursue more equity strongly so they are more sensitive to unfair information in the early stage. In a word, we should provide more fair allocations for deaf college students in our harmonious society.

Introduction: The present study was designed to examine the effect of monetary and non-monetary endowment on lying by men and women in the Ultimatum Game. Another goal was to examine to what extent the Self-Reported Lying Scale (SRLS), described here for the first time, predicts lying in the Ultimatum Game. Methods: Examinees (162, 82 women) were allocated to four experimental conditions in a 2 × 2 factorial design. Two endowment conditions (money and game points) were crossed with two sex conditions (men and women). Participants underwent an Ultimatum Game in which they were permitted to conceal part of the endowment froman unidentified partner. Finally, participants completed the SRLS. Results: The results indicated that more cash than points were concealed from the partner, and men concealed more of their endowment than women. We further defined fake fairness in sharing that combined hiding a more significant portion of the endowment from the partner while presenting fair sharing of the remaining award. We found more fake fairness when money was shared than when points were concealed. Fake fairness is more significant for men than for women. For money and points alike, concealment was predicted by the global score of the SRLS and its five subscales (self-assessed lying ability, lie detection ability, the use of reason in lying, lie acceptability, and lie frequency). Discussion: It was suggested that a monetary endowment is more sensitive to lying than game points and involves more fake fairness. Nevertheless, the differences are quantitative, and the same response pattern exists in the two endowment conditions. Replacing money with points is a proper solution whenever a monetary endowment presents difficulties. It was further suggested that sex differences exist in lying using an asymmetric information UG, where proposers were permitted tomislead responders about their endowment. Finally, the SRLS may contribute to a better understanding of the question of who lies. [ABSTRACT FROM AUTHOR]

We propose an ultimatum bargaining model in which the parties experience an envy-based externality that is private information. Our results indicate that there is a threshold for the proposer's envy which determines whether there will be either a perfectly equitable, certain agreement or an uncertain, inequitable agreement, and that this threshold rises as the distribution of the responder's envy level improves in a first-order stochastic-dominance sense. In addition, conditionally on the scenario ruling out a perfectly equitable agreement, we show that the proposer's envy level plays a dual role: (i) it increases the probability of a negotiation breakdown, and (ii) it constitutes a source of bargaining power. Numerical simulations also allow us to explore some properties of the role played by the responder's envy and by changes in the envy distributions of the two players. Overall, our theoretical results are consistent with the main evidence from ultimatum experiments conducted in behavioral and neuroscience settings. In addition, we provide testable implications of our model for future experiments. • An ultimatum bargaining model with envy and asymmetric information is proposed. • A cutoff for the proposer's envy level determines equitable or inequitable agreements. • This cutoff rises with first-order-stochastic improvements of the responder's envy. • Proposer's envy level increases disagreement probability and confers bargaining power. • Our results are consistent with behavioral evidence and provide testable implications. [ABSTRACT FROM AUTHOR]

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Pre-play non-binding communication in organizations is prevalent. We study the implications of pre-play, private and public, wage proposals in labor markets. To that end, we develop a theoretical model from which we derive certain hypothesis that we test through a laboratory experiment. In the baseline, that depicts a typical labor market interaction, the employer makes a wage offer to the worker who may then accept or reject it. In subsequent treatments, workers, moving first, make private, non-binding, wage proposals to the employer. In a following treatment, the proposals are made public. Our findings suggest that both private and public wage proposals promote higher wages, efficiency, and income equality. Public information on wage proposals benefits firms more than workers while, workers benefit more under private proposals where income inequality is the lowest. We find some support in our data on workers conforming to their co-workers' wage proposals when these are public. Finally, the gender gap observed in the baseline on acceptance rates and workers' income vanishes when proposals are present. [ABSTRACT FROM AUTHOR]

Face masks play a pivotal role in the control of respiratory diseases, such as the novel coronavirus (COVID-19). Despite their widespread use, little is known about how face masks affect human social interaction. Using unique experimental data collected early on in the pandemic, we investigate how facial occlusion by face masks alters socio-economic exchange. In a behavioral economics study (N = 481), individuals accepted more monetary offers and lower offer amounts when interacting with a masked versus unmasked opponent. Importantly, this effect was mainly driven by faces covered with surgical masks relative to bandana-type masks. In the first weeks of mask use during the COVID-19 pandemic, motive attributions further moderated this effect: Participants who believed that mask wearers were seeking to protect others showed the highest acceptance rates. Overall, we describe a new phenomenon, the face-mask effect on socio-economic exchange, and show that it is modulated by contextual factors. [ABSTRACT FROM AUTHOR]

In this paper we review, upgrade, and synthesize existing models from evolutionary game theory, all of which aim at explaining human behaviour in the ultimatum game. Our new and improved versions of Gale et al. (1995) , Nowak et al. (2000) , and Rand et al. (2013) avoid shortcomings that the original versions have, one of which is that the results in the first and the last are driven by bias in the mutations. We also compare the predictions of these three models with the existing experimental evidence by looking at properties of the distributions of minimal acceptable offers. We find that the observed distributions do not conform to the predictions from Gale et al. (1995) , Rand et al. (2013) , or any other model in which there is no fitness benefit to rejecting. This does not rule out commitment-based explanations, such as Nowak et al. (2000). [ABSTRACT FROM AUTHOR]

Inarguably, humans perform the richest plethora of prosocial behaviours in the animal kingdom, and these are important for understanding how humans navigate their social environment. The success and failure of strategies human players devise also have implications for determining long-term socio-economic/evolutionary fitness. Following the footsteps of Press and Dyson (2012), I implemented their evolutionary game-theoretic modelling from Iterated Prisoner’s Dilemma (a behavioural economic probe of interpersonal cooperation) and re-analysed already published data on human proposer behaviour in the Ultimatum Game (a behavioural economic probe of altruistic punishment) involving 50 human participants versus stochastic computerized opponents with prosocial and individualistic social value orientations. Although the results indicate that it is more likely to break cycles of mutual defection in ecosystems in which humans interact with individualistic opponents, analysis of social-economic fitness at the Markov stationary states suggested that this comes at an evolutionary cost. Overall, human players acted in a significantly more cooperative manner than their opponents, but they failed to overcome extortion from individualistic agents, risking ‘extinction’ in 70% of the cases. These findings demonstrate human players might be short-sighted, and social interactive decision strategies they devise while adjusting to different types of opponents may not be optimal in the long run.

IntroductionHuman decision-making pertaining to gains compared to those pertaining losses is shown to be quite different. However, mixed evidence is provided regarding the effect on the decision-makers' prosocial behaviors; that is, losses are shown to either increase or decrease prosocial behaviors. In this context, the effect of social norms on observed behavior can play a crucial role.MethodsTo examine this aspect in more detail, we conducted incentivized ultimatum game experiments and analyzed data from three treatments, the control treatments (without specific norm focus), and two different norm-focus treatments (“average behavior” treatment and “self-interested behavior” treatment). In total, 550 participants took part in our experiment. Basically, we found no significant difference between the division of gains and losses in the “control” and “self-interested behavior” treatments.Results and discussionHowever, we found such a difference in the “average behavior” treatment. In addition, we found that inducing a norm focus leads to less variance in proposers' behavior and a greater concentration of their demands around the induced norm in the “average behavior” treatment. In contrast, we found a higher variance in proposers' behavior in the “self-interested behavior” treatment. In terms of responders' behaviors, we observed a tendency toward a higher frequency of responders' rejections in the loss domain compared to the gains domain.

Ran-Ran Zhang,1,2,* Yu-Qing Meng,1,* Yan Tian,1 Tao Zou3 1School of Medical Humanities, Guizhou Medical University, Guizhou, 550004, People’s Republic of China; 2Researcher, Guizhou Health Development Research Center, Guizhou, 550004, People’s Republic of China; 3Department of Psychiatry, Affiliated Hospital of Guizhou Medical University, Guizhou, 550004, People’s Republic of China*These authors contributed equally to this workCorrespondence: Tao Zou, Department of Psychiatry, Affiliated Hospital of Guizhou Medical University, Guizhou, 550004, People’s Republic of China, Tel +8613985400734, Email zoutaozou@tom.comPurpose: Most studies have supported the view that individuals prefer to reward the in-group and discriminate against the out-group in response to unfair offers in the Ultimatum Game. However, the current study advanced a different view, that is, the “black sheep effect”, in which in-group members were punished more severely compared with out-group members. This study aimed to incorporate proposer identity and allocation motive as possible explanations for offer rejection.Methods: In the current study, the in-group and out-group identities were distinguished by their health condition, and the allocation motive was defined according to its benefit maximization. With a total of 89 healthy college student participants, a mixed design of 2 (proposer identity: out-group vs in-group) × 2 (allocation motive: selfish vs random) × 2 (offer type: unfair vs fair) was used in the Ultimatum Game. Event-related potential (ERP) technology was used, and ERPs were recorded while participants processed the task.Results: The behavioral result showed that the “black sheep effect” was found on the fair offer when a random allocation motive was used. Our ERP result suggested that feedback-related negativity (FRN) and P300 were modulated by proposer identity but not by allocation motive. However, the allocation motive interacted with proposer identity affecting FRN and P300 when the fair offer was proposed.Conclusion: These findings demonstrated that the “black sheep effect” was related to the experience of the out-group member, such as disadvantage or distress, but it was also modulated by allocation motive. Meanwhile, the out-group (depressed college students) captured more attention because they violated individual expectations, according to the P300. This finding plays an integral role in understanding the mechanism of response to the “black sheep effect”.Plain Language Summary: People prefer to receive fair offers compared to unfair offers, but they are more tolerant to in-group members compared with out-group members when facing unfair offers. However, what would you do if you knew the in-group members were making you the smallest offer possible with a self-interested motive to maximize their own gains? We used the Ultimatum Game (UG) to explore this issue. We invited 89 colleges to participate in this study, and they were randomly divided into in-group member, out-group member, selfish motive, and random motive groups. Then, we used event-related potential (ERP) technology to examine cognitive processing. We found the “back sheep effect” on the fair offer, which means that people prefer to accept the out-group member’s offer when they had a random motive. We also found different feedback-related negativity (FRN) and P300 between the in-group and out-group members. In addition, the “black sheep effect” was found in the fair offers when the proposer presented a random motive. This finding plays an important role in understanding the mechanism of response to fair or unfair offers.Keywords: in-group, out-group, ultimatum game, event-related potential technique, allocation motive, feedback-related negativity, P300

The ultimatum game (UG) is widely used to investigate our sense of fairness, a key characteristic that differentiates us from our closest living relatives, bonobos and chimpanzees. Previous studies found that, in general, great apes behave as rational maximizers in the UG. Proposers tend to choose self-maximizing offers, while responders accept most non-zero offers. These studies do not rule out the possibility that apes can behave prosocially to improve the returns for themselves and others. However, this has never been well studied. In this study, we offer chimpanzee and bonobo proposers the possibility of taking into account the leverage of responders over the offers they receive. This leverage takes the form of access to alternatives for responders. We find that proposers tend to propose fairer offers when responders have the option to access alternatives. Furthermore, we find that both species use their leverage to reject unequal offers. Our results suggest that great apes mostly act as rational maximizers in an UG, yet access to alternatives can lead them to change their strategies such as not choosing the self-maximizing offer as proposers and not accepting every offer higher than zero as responders.

IntroductionThe present study was designed to examine the effect of monetary and non-monetary endowment on lying by men and women in the Ultimatum Game. Another goal was to examine to what extent the Self-Reported Lying Scale (SRLS), described here for the first time, predicts lying in the Ultimatum Game.MethodsExaminees (162, 82 women) were allocated to four experimental conditions in a 2 × 2 factorial design. Two endowment conditions (money and game points) were crossed with two sex conditions (men and women). Participants underwent an Ultimatum Game in which they were permitted to conceal part of the endowment from an unidentified partner. Finally, participants completed the SRLS.ResultsThe results indicated that more cash than points were concealed from the partner, and men concealed more of their endowment than women. We further defined fake fairness in sharing that combined hiding a more significant portion of the endowment from the partner while presenting fair sharing of the remaining award. We found more fake fairness when money was shared than when points were concealed. Fake fairness is more significant for men than for women. For money and points alike, concealment was predicted by the global score of the SRLS and its five subscales (self-assessed lying ability, lie detection ability, the use of reason in lying, lie acceptability, and lie frequency).DiscussionIt was suggested that a monetary endowment is more sensitive to lying than game points and involves more fake fairness. Nevertheless, the differences are quantitative, and the same response pattern exists in the two endowment conditions. Replacing money with points is a proper solution whenever a monetary endowment presents difficulties. It was further suggested that sex differences exist in lying using an asymmetric information UG, where proposers were permitted to mislead responders about their endowment. Finally, the SRLS may contribute to a better understanding of the question of who lies.

Objective: we analyzed decision-making under stress by manipulating salivary cortisol levels. Theoretical background: literature dedicated to the relationship between stress and decision-making is still inconclusive. Studies have found that when dealing with stressful decisions, people will respond with a greater propensity for opportunistic behavior. However, stress might also decrease the potential for deception when the decision requires strategic/analytical responses. Method: we implemented a laboratory experiment using the ultimatum game with asymmetric information, in which only the first mover was fully informed about the size of the endowment. Our experiment compared the decisions of subjects who received a stress stimulus from an adapted Trier social stress test for groups (TSST-G) protocol with a control group. Results: we found that under stress, proposers transferred more to responders. In contrast, non-stressed players were more likely to take advantage of information asymmetry by choosing lower strategic offers, which is consistent with the so-called ‘hide behind a small cake’ effect. Regression analysis also indicated that larger offers are not necessarily associated with increased prosocial motives since stressed proposers became more confident about the responder’s ability to guess the true endowment, which decreased their incentive to take advantage of the aforementioned effect. Conclusions: one possible effect of stress could be an increase in risk perception, decreasing the ability to make strategic decisions. The stressful condition might have rendered our participants less capable of realizing the ‘hide behind a small cake’ potential of the game, leading them to make more conservative offers when compared to the control group.

Agency theory posits that the separation of ownership and control in a company allows self-interested managers to pursue their own interests by taking advantage of their superior information compared to shareholders. In this paper, we present evidence that agency costs (i.e., flawed director decision-making) can arise because of directors' limited competence and the problem of specification of objectives, independent of information asymmetry and director independence. Using a 2x2 experimental design addressed to 180 directors, we demonstrate that anchors (Angeletos & Huo, 2021) and the mechanism of fairness (Mussel et al., 2022) may cause directors to deviate from the rational choice that maximizes a given utility function. We argue that the decisionmaking process can undermine a director's ability to effectively monitor by exploiting their limited rationality, and this aspect remains inadequately specified in existing agency models. Consequently, we contribute to the literature that examines the board as a decision-making group by showcasing how a focused analysis of the decision process can unveil new mechanisms within the governance process. [ABSTRACT FROM AUTHOR]

Depression and social anxiety are common disorders that have a profound impact on social functioning. The need for studying the neural substrates of social interactions in mental disorders using interactive tasks has been emphasized. The field of neuroeconomics, which combines neuroscience techniques and behavioral economics multiplayer tasks such as the Ultimatum Game (UG), can contribute in this direction. We assessed emotions, behavior, and Event‐Related Potentials in participants with depression and/or social anxiety symptoms (MD/SA, n = 63, 57 females) and healthy controls (n = 72, 67 females), while they played the UG. In this task, participants received fair, mid‐value, and unfair offers from other players. Mixed linear models were implemented to assess trial level changes in neural activity. The MD/SA group reported higher levels of sadness in response to mid‐value and unfair offers compared to controls. In controls, the Medial Frontal Negativity associated with fair offers increased over time, while this dynamic was not observed in the MD/SA group. The MD/SA group showed a decreased P3/LPP in all offers, compared to controls. These results indicate an enhanced negative emotional response to unfairness in the MD/SA group. Neural results reveal a blunted response over time to positive social stimuli in the MD/SA group. Moreover, between‐group differences in P3/LPP may relate to a reduced saliency of offers and/or to a reduced availability of resources for processing incoming stimuli in the MD/SA group. Findings may shed light into the neural substrates of social difficulties in these disorders. It is crucial to study the neural substrates of social interactions in mental health using interactive tasks that immerse the participant in a social context. The Ultimatum Game was used to assess ERPs to fair, mid‐value, and unfair offers from others in depressed and/or socially anxious volunteers. We found blunted neural responses over time to fair offers as well as reduced availability of resources for processing incoming social stimuli in depression and social anxiety. [ABSTRACT FROM AUTHOR]

Empirical and experimental evidence suggests that individual behavior in group interactions is affected by perceived norms of behavior within the group. We design an experiment to test this hypothesis. We find that (a) when agents interact within a group, the initial diverse behaviors converge to the group average and individuals cluster more tightly around this benchmark as they learn the average, (b) actions further from this benchmark in a self-serving direction are less acceptable by others, and (c) when an agent is moved to a group with a different benchmark, s/he conforms quickly to the new benchmark. [ABSTRACT FROM AUTHOR]

We examine preference for randomization, and link it to conflicting preference-led indecisiveness in social settings. In an ultimatum game experiment where receivers may face conflicting preferences between material gains and equity, we allow receivers to assign non-zero probabilities to both acceptance and rejection (the randomized choice) in addition to the standard binary choice of acceptance or rejection. We further elicit receivers' willingness to pay for using the randomized choice instead of the binary choice. We find that a theoretical model incorporating receivers' conflicting preferences explains the experimental results well: most receivers randomized actively between acceptance and rejection, and many were willing to pay for randomization. Our results suggest that allowing people to randomize when making choices with conflicting preferences may improve individual welfare. [ABSTRACT FROM AUTHOR]

Considerable Ultimatum Game studies suggest that individuals tend to reject unfair offers even at the cost of personal financial loss. Different from prior studies in which the ultimatum game allocations are often certain (e.g., $2: $8), the current research examines whether uncertain allocations (e.g., $1–$3: $7–$9) alter the rejections in two incentive compatible studies. That is, whether unfair offers influence rejection rates in ultimatum game decisions. Study 1 showed that decision makers are generally less likely to reject unfair offers when they are uncertain (between $1 and $3) rather than certain ($2). Study 2 replicated the effect and further revealed a boundary: when the range of the uncertain offer includes zero such that there is a possibility of receiving nothing, decision makers exhibited similar rejection rates for uncertain and certain unfair offers. [ABSTRACT FROM AUTHOR]

We report experimental findings on distribution decisions by Germans and Egyptians. We explore their sensitivity along three different dimensions: we study (i) the impact of the price of giving, (ii) how giving responds to the cultural and gender identity of the recipient, and (iii) how a threat of rejection in a bargaining situation affects the distribution choice. We show substantial differences in generosity between participants in Egypt vs. Germany, the former showing substantial equality-seeking behavior. Correspondingly, both genders in Egypt increase giving when it becomes more costly as do German females, in contrast to German males who give particularly when it is cheap. While Egyptian participants choose according to an equality norm independently of the recipient's identity, we detect substantial discrimination by German females when giving to Egyptian males. This discrimination is in line with prejudice as males in Egypt give significantly more than what Germans expect from them. Conversely, males in Egypt overestimate the generosity of Germans towards them. We finally show that, relative to giving in the dictator game, the ultimatum game offers increase among German participants, but not among participants in Egypt. Females in Egypt even decrease giving in UG relative to DG when allocating to males in Egypt. This finding is in line with highly favorable offers being rejected by a substantial fraction of participants in Egypt. [ABSTRACT FROM AUTHOR]

People tend to dislike and punish unfair behaviors in social interactions, and this disposition may be moderated by the characteristics of their interaction partner. We used a modified ultimatum game (UG) to investigate players' responses to fair and unfair offers from proposers described as having performed either a moral transgression or a neutral behavior, and recorded an electroencephalogram. The participants' behavior in the UG suggests that people quickly demand more fairness from proposers who have committed moral transgressions rather than neutral behavior. Event-related potentials (ERPs) revealed a significant effect of offer type and of proposer type on P300 activity. The prestimulus α-oscillation power in the neutral behavior condition was significantly lower than that in the moral transgression condition. The post-stimulus β-event-related synchronization (β-ERS) was larger for the moral transgression condition than the neutral behavior condition in response to the least fair offers, and larger for neutral behavior than the moral transgression condition in response to the fairest offers. In summary, β-ERS was influenced by both proposer type and offer type, which revealed different neural responses to the offer from either a morally transgressive or a neutral behavior proposer. • People reject offers from the moral violator more often and more quickly. • The offers from the moral violators induced larger P300. • Proposer's moral behaviors induced significantly larger prestimulus α-oscillation. • Proposer's behaviors influenced β-ERS when offers are the fairest or unfairest. [ABSTRACT FROM AUTHOR]

With technological developments, individuals are increasingly able to delegate tasks to autonomous agents that act on their behalf. This may cause individuals to behave more fairly, as involving an agent representative encourages individuals to strategise ahead and therefore adhere to social norms of fairness. Research suggests that an audio smiling agent may further promote fairness as it provides a signal of honesty and trust. What is still unclear is whether presenting a multimodal smiling agent (by using visual and auditory cues) rather than a unimodal smiling agent as normally available commercially (using only an auditory cue e.g., Siri) could amplify the impact of smiles. In the present study, participants (N = 86) played an ultimatum game either directly with another player (control), through a smiling multimodal and unimodal agent or through a neutral multimodal and unimodal agent. Participants' task was to offer a number of tickets to the other player from a fixed amount. Results showed that when playing the ultimatum game through a smiling multimodal agent, participants offered more tickets to the other player compared to the control condition and the other agent conditions. Hence, exploiting multisensory perception to enhance an agent's expression may be key for increasing individuals' pro-social behaviour when interacting through such an agent. [ABSTRACT FROM AUTHOR]

The present research investigated the role of sex in the effect of vocal attractiveness on fairness judgment in a two-person Ultimatum Game. Each participant in the game decided whether to accept offers from a proposer who was either associated with an attractive or unattractive voice. The results showed that while participants were more likely to accept fair offers, they would also accept some unfair offers that were associated with an attractive voice. This effect of vocal attractiveness was more clearly shown by female participants, although all male and female participants took longer to make a decision when an attractive voice was associated with an offer, regardless of whether the voice was from the same sex or the opposite sex. Overall, the results inform the role of sex in the effect of vocal attractiveness and further confirm the beauty premium effect on economic bargaining, where people with an attractive voice would benefit. [ABSTRACT FROM AUTHOR]

This study examined the cognitive predictors and constraints of children's strategic offers in the Ultimatum Game. The Ultimatum Game is a one-shot negotiation on the division of a given sum of rewards between two people, where the receiver has the right to punish the proposer by rejecting unfair offers, which results in nil reward for either party. Ninety-four Hong Kong children ranged between three and six years of age (48 girls, M = 4.94, SD = 0.90) participated in an Ultimatum Game, and tasks measuring theory of mind, cognitive flexibility, inhibitory control and verbal ability. Children's theory of mind, measured with false belief understanding tasks, was positively associated with their Ultimatum Game offers. Regression analysis further demonstrated that cognitive flexibility moderated the association between false belief understanding and children's offers in the Ultimatum Game. Being able to take the opponent's perspective prompted children to offer more in the Ultimatum Game, but only when their cognitive flexibility was low. [ABSTRACT FROM AUTHOR]

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Widely regarded as the cornerstone of justice (Rawls, 1971),fairness constitutes one of the pillars of human morality. TheUltimatum Game (UG), extensively studied in behavioral eco-nomics, is the canonical task for studying fairness. In sharpcontrast to the predictions of normative standards in game the-ory, people typically reject low offers in UG. In this work,we present the first resource-rational process model of UG.Concretely, by taking into account people’s expectations, weshow that Nobandegani et al.’s (2018) resource-rational pro-cess model, sample-based expected-utility, provides a unifiedaccount of several experimental findings in UG, namely, theeffects of expectation, competition, and time pressure. Assum-ing that expectation serves as a reference point for subjectivevaluation of an offer, we show that the rejection of low offers inUG can arise from purely self-interested expected-utility max-imization. We conclude by discussing the implication of ourwork for moral decision-making and, more broadly, human ra-tionality.