Social status modulates the neural response to unfairness

Receivers' responses are integrated into costly third-party punishment in a way that interacts with the unfairness of allocations

Costly third-party punishment (TPP) is an effective way to enforce fairness norms and promote cooperation. Recent studies have shown that the third party considers not only the proposer's suggested allocation but also the receiver's response to the allocation, which was typically ignored in traditional TPP studies when making punishment decisions. However, it remains unclear whether and how the varying unfair allocations and receivers' responses are integrated into third-party punishment. The current study addressed these issues at behavioral and electrophysiological levels by employing a modified third-party punishment task involving proposers' highly or moderately unfair allocations and the receivers' acceptance or rejection responses. At the behavioral level, participants punished proposers more often when receivers rejected relative to accepted unfair allocations. This effect was further modulated by the unfairness degree of allocations, indicated by a more pronounced rejection-sensitive effect when participants observed the moderately unfair offers. Electrophysiologically, when the receiver rejected the moderately unfair allocations, a stronger late-stage component P300/LPP, which was considered to be involved in allocations of attention resources, was found. Meanwhile, separated from the P300/LPP, the P200 associated with early attention capture demonstrated a rejection-sensitive effect. Together, in the costly TPP studies, the receiver is typically designated as passive and silent, and her/his responses to unfairness are conventionally ignored. However, our results indicate that except for the proposer's distribution behavior, the receiver's response does have an impact on third-party punishment in a way that interacts with the unfairness of allocations.

Social status mediates the propagation of unfairness

Fairness constitutes a cornerstone of social norms, emphasizing equal treatment and equitable distribution in interpersonal relationships. Unfair treatment often leads to direct responses and can spread to others through a phenomenon known as pay-it-forward (PIF) reciprocity. This study examined how unfairness spreads in interactions with new partners who have higher, equal, or lower status than the participants. In the present study, participants (N = 47, all Korean) were given either fair or unfair treatment in the first round of a dictator game. They then allocated monetary resources among partners positioned at various hierarchical levels in the second round. Our main goal was to determine if the severity of inequity inflicted on new partners was influenced by their hierarchical status. The results revealed an inclination among participants to act more generously towards partners of higher ranking despite prior instances of unfair treatment, whereas a tendency for harsher treatment was directed towards those with lower ranking. The interaction between the fairness in the first round (DG1) and the hierarchical status of the partner in the second round (DG2) was significant, indicating that the effect of previous fairness on decision-making differed depending on the ranking of the new partners. This study, therefore, validates the presence of unfairness PIF reciprocity within hierarchical contexts.

Spontaneous brain activity associated with individual differences in decisional and emotional forgiveness

Previous studies have explored the neural bases of forgiveness, however, the neural associations of decisional and emotional forgiveness remain unclear. Regional homogeneity (ReHo) and functional connectivity (FC) measured by resting-state functional magnetic resonance imaging (fMRI) were used to investigate the neural associations of individual differences in decisional and emotional forgiveness among healthy volunteers (256 participants, 85 males). The results of the ReHo analysis showed that decisional forgiveness was positively correlated with the left inferior parietal lobule (IPL). Furthermore, emotional forgiveness was positively correlated with the dorsal anterior cingulate cortex (dACC) and left supramarginal gyrus (SMG). The results of the FC analysis showed that decisional forgiveness was positively associated with the FC strength between the left IPL and left middle frontal gyrus (MFG) and negatively correlated with the FC strength among the left IPL, right superior temporal gyrus (STG), and left SMG. Furthermore, there was a significant positive correlation between emotional forgiveness and FC strength between the left SMG and right IPL. These findings suggest an association between decisional and emotional forgiveness and spontaneous brain activity in brain regions related to empathy, emotion regulation, and cognitive control.

Reconfiguration of the costly punishment network architecture in punishment decision-making

Human costly punishment is rooted in multiple regions across large-scale functional systems, a collection of which constitutes the costly punishment network (CPN). Our previous study found that the CPN is intrinsically organized in an optimized and reliable manner to support individual costly punishment propensity. However, it remains unknown how the CPN is reconfigured in response to external cognitive demands in punishment decision-making. Here, we combined resting-state and task-functional magnetic resonance imaging to examine the task-related reconfigurations of intrinsic organizations of the CPN when participants made decisions of costly punishment in the Ultimatum Game. Although a strong consistency was observed in the overall pattern and each nodal profile between the intrinsic (task-free) and extrinsic (task-evoked) functional connectivity of the CPN, condition-general and condition-specific reconfigurations were also evident. Specifically, both unfair and fair conditions induced increases in functional connectivity between a few specific pairs of regions, and the unfair condition additionally induced increases in network efficiency of the CPN. Intriguingly, the specific changes in global efficiency of the CPN in the unfair condition were associated with individual differences in costly punishment after adjusting for the corresponding results in the fair condition, which were further identified for females but not for males. These findings were largely reproducible on independent samples. Collectively, our findings provide novel insights into how the CPN adaptively reconfigures its network architecture to support costly punishment.

A Brain-To-Brain Mechanism for Social Transmission of Threat Learning

Survival and adaptation in environments require swift and efficacious learning about what is dangerous. Across species, much of such threat learning is acquired socially, e.g., through the observation of others' ("demonstrators'") defensive behaviors. However, the specific neural mechanisms responsible for the integration of information shared between demonstrators and observers remain largely unknown. This dearth of knowledge is addressed by performing magnetoencephalography (MEG) neuroimaging in demonstrator-observer dyads. A set of stimuli are first shown to a demonstrator whose defensive responses are filmed and later presented to an observer, while neuronal activity is recorded sequentially from both individuals who never interacted directly. These results show that brain-to-brain coupling (BtBC) in the fronto-limbic circuit (including insula, ventromedial, and dorsolateral prefrontal cortex) within demonstrator-observer dyads predict subsequent expressions of learning in the observer. Importantly, the predictive power of BtBC magnifies when a threat is imminent to the demonstrator. Furthermore, BtBC depends on how observers perceive their social status relative to the demonstrator, likely driven by shared attention and emotion, as bolstered by dyadic pupillary coupling. Taken together, this study describes a brain-to-brain mechanism for social threat learning, involving BtBC, which reflects social relationships and predicts adaptive, learned behaviors.

Younger adults are more prosocial than older adults in economic decision making results from the give and take game

The present study was designed to investigate the disadvantageous and advantageous inequity aversion of young and older adults in situations which allowed them to maximize or minimize payoff inequalities. Given the very limited evidence regarding an actual age-related effect on inequity aversion, the purpose of this study was to examine this question using an economic game, "the Give-and-Take Game", which is able to circumvent certain limitations of the Ultimatum Game, to evaluate inequity aversion (i.e., a same behaviour which can be induced by opposite motivations: prosocial vs. pro-self vs. altruistic orientations). In the "Give-and-Take Game", a sum of money was randomly distributed between the participant and a dummy player. These distributions created monetary inequalities, advantageous either for the participant (to examine advantageous inequity aversion) or for the other player (to examine disadvantageous inequity aversion). Different response options were proposed to the participants to either maximize or minimize payoff inequalities between the players. This procedure not only allowed to differentiate individual's profiles with more prosocial vs. pro-self vs. altruistic orientations, but also to examine age-related effects on these profiles. The results showed that older adults showed a more important pro-self orientation compared to their younger counterparts. They more frequently selected the options which maximized their own payoffs and were less averse to advantageous inequity compared to young adults. In contrast, young adults showed a similar level of advantageous and disadvantageous inequity aversion. Older adults focused on the economic and competitive dimension of the game, which may have motivated them to maximize their own payoffs. Conversely, young adults took into account the social dimension of the game, focusing on a fair monetary distribution.

Neurocomputational evidence that conflicting prosocial motives guide distributive justice

In the history of humanity, most conflicts within and between societies have originated from perceived inequality in resource distribution. How humans achieve and maintain distributive justice has therefore been an intensely studied issue. However, most research on the corresponding psychological processes has focused on inequality aversion and has been largely agnostic of other motives that may either align or oppose this behavioral tendency. Here we provide behavioral, computational, and neuroimaging evidence that distribution decisions are guided by three distinct motives-inequality aversion, harm aversion, and rank reversal aversion-that interact with each other and can also deter individuals from pursuing equality. At the neural level, we show that these three motives are encoded by separate neural systems, compete for representation in various brain areas processing equality and harm signals, and are integrated in the striatum, which functions as a crucial hub for translating the motives to behavior. Our findings provide a comprehensive framework for understanding the cognitive and biological processes by which multiple prosocial motives are coordinated in the brain to guide redistribution behaviors. This framework enhances our understanding of the brain mechanisms underlying equality-related behavior, suggests possible neural origins of individual differences in social preferences, and provides a new pathway to understand the cognitive and neural basis of clinical disorders with impaired social functions.

Neural responses to social partners' facial expressions are modulated by their social status in an interactive situation

Recently, several studies have found a recognition advantage for facial expressions, particularly angry expressions, when they appear on high-status faces rather than low-status faces. In the present study, we used event-related potentials (ERPs) to explore the influence of social status on the neural responses to others' facial expressions in a context of performance monitoring. Specifically, we used an interactive rank-inducing task (i.e., time estimation task) to manipulate social partners' status (high versus low) and then told participants that they would receive social feedback (i.e., happy, neutral, or angry) from social partners with high or low status after completing the task. ERP results revealed the preferential processing of high-status targets at both early (P1/N170/FRN) and late (P3) temporal stages of facial expression processing. Notably, larger FRN amplitudes elicited by feedback from high-status partners were observed in happy, neutral, and angry expression contexts, whereas larger P3 amplitudes elicited by feedback from high-status partners were only evident in both neutral and angry expression contexts but not in happy expression context. Together, the present study extended previous studies by showing that the perception of facial expressions could be modulated by target status at multiple stages.

Superior bias in trust-related decisions

Trust is conditional. Many studies have revealed its relative conditions in different situations, but when social status is characteristic of the person who receives trust (the “trustee”), our knowledge of how social status affects trust still remains limited. In this study, we used the trust game in order to: (1) characterize the effect of trustees’ social hierarchy on trust-related decisions in different trustworthiness situations and (2) explore the underlying computational process regarding the impact that social status has on trust-related decisions by using the computational modeling approach to integrate social status into trust-related situations. In Experiment 1, using a one-shot trust game with no feedback of information about reciprocity, we found that compared with inferiors, superiors gained more trust-related behaviors (investments) in spite of the fact that they were not rated as having higher trustworthiness. Then, in Experiment 2, when we controlled the trustworthiness of different social status partners by providing the same neutral reciprocity rate (50%) in a repeated trust game, the high-status partner gained more trust than the low-status partner. This superior bias extended to Experiment 3a and 3b, in which we set different levels of trustworthiness to match the different social statuses of partners. With respect to modeling results, we found that higher status holds an additional social value independent of trust profit, resulting in superior bias. Ultimately, this study has shed light on the superior bias that commonly leads people to grant high-status individuals goodwill in social interactions.

You are excusable! Neural correlates of economic neediness on empathic concern and fairness perception

There is ample experimental evidence showing that the proposers' social role is related to individuals' fairness perception in the Ultimatum Game (UG). However, various social roles, e.g., degree of economic neediness, have different influences on fairness perception, yet it has not been well studied. In this study, we adapted the UG paradigm and recorded electroencephalography (EEG) to probe the neural signatures of whether and how the degree of neediness influences fairness perception. Behavioral results showed that responders are prone to accept unfair offers from proposers in need more than those who are not in need. At the brain level, MFN (medial frontal negativity) was more negative-going in response to unfair than fair offers for not-in-need proposers. In contrast, we found a reversed MFN difference response to unfair and fair offers for in-need proposers, showing a strongly pure altruistic phenomenon. Moreover, we found smaller P300 amplitude was induced in the proposer-in-need condition, compared with its counterpart, while a negative correlation between empathy rating and P300 amplitude in the proposer-in-need condition regardless of the offers' fairness. The current results indicate that the degree of neediness might reduce fairness perception by promoting the empathic concern toward the in-need proposers rather than decreasing the empathic concern for the not-in-need proposers.

Effects of Transcranial Direct Current Stimulation Over the Right Dorsolateral Prefrontal Cortex on Fairness-Related Decision-Making

Neuroimaging studies suggest that the right dorsolateral prefrontal cortex (rDLPFC) is an important brain area involved in fairness-related decision-making. In the present study, we used transcranial direct current stimulation (tDCS) over the rDLPFC to investigate the effects of changed cortical excitability on fairness norm enforcement in social decision-making. Participants received anodal, cathodal, or sham stimulation before performing a modified ultimatum game (UG) task, in which participants were asked to accept or reject the proposer's offer and self-rate the intensity of their anger at offers on a 7-point scale. The results showed that the rejection rate of unfair offers and anger level were higher in the anodal compared to the sham and cathodal groups, and that the level of anger at unfair offers can predict the rejection rate. Furthermore, the fairness effect of RTs was more prominent in the anodal group than in the sham and cathodal groups. Our findings validate the causal role of the rDLPFC in fairness-related decision-making through tDCS, suggesting that strengthening the rDLPFC increases individuals' reciprocal fairness in social decision-making, both in subjective rating and behaviors.

Integration of social status and trust through interpersonal brain synchronization

Trust can be a dynamic social process, during which the social identity of the interacting agents (e.g., an investor and a trustee) can bias trust outcomes. Here, we investigated how social status modulates trust and the neural mechanisms underlying this process. An investor and a trustee performed a 10-round repeated trust game while their brain activity was being simultaneously recorded using functional near-infrared spectroscopy. The social status (either high or low) of both investors and trustees was manipulated via a math competition task. The behavioral results showed that in the initial round, individuals invested more in low-status partners. However, the investment ratio increased faster as the number of rounds increased during trust interaction when individuals were paired with a high-status partner. This increasing trend was particularly prominent in the low (investor)-high (trustee) status group. Moreover, the low-high group showed increased investor-trustee brain synchronization in the right temporoparietal junction as the number of rounds increased, while brain activation in the right dorsolateral prefrontal cortex of the investor decreased as the number of rounds increased. Both interpersonal brain synchronization and brain activation predicted investment performance at the early stage; furthermore, two-brain data provided earlier predictions than did single-brain data. These effects were detectable in the investment phase in the low-high group only; no comparable effects were observed in the repayment phase or other groups. Overall, this study demonstrated a multi-brain mechanism for the integration of social status and trust.

A meta-analysis on shared and distinct neural correlates of the decision-making underlying altruistic and retaliatory punishment

Individuals who violate social norms will most likely face social punishment sanctions. Those sanctions are based on different motivation aspects, depending on the context. Altruistic punishment occurs if punishment aims to re‐establish the social norms even at cost for the punisher. Retaliatory punishment is driven by anger or spite and aims to harm the other. While neuroimaging research highlighted the neural networks supporting decision‐making in both types of punishment in isolation, it remains unclear whether they rely on the same or distinct neural systems. We ran an activation likelihood estimation meta‐analysis on functional magnetic resonance imaging data on 24 altruistic and 19 retaliatory punishment studies to investigate the neural correlates of decision‐making underlying social punishment and whether altruistic and retaliatory punishments share similar brain networks. Social punishment reliably activated the bilateral insula, inferior frontal gyrus, midcingulate cortex (MCC), and superior and medial frontal gyri. This network largely overlapped with activation clusters found for altruistic punishment. However, retaliatory punishment revealed only one cluster in a posterior part of the MCC, which was not recruited in altruistic punishment. Our results support previous models on social punishment and highlight differential involvement of the MCC in altruistic and retaliatory punishments, reflecting the underlying different motivations.

The neural signatures of social hierarchy-related learning and interaction: A coordinate- and connectivity-based meta-analysis

Numerous neuroimaging studies have investigated the neural mechanisms of two mutually independent yet closely related cognitive processes aiding humans to navigate complex societies: social hierarchy-related learning (SH-RL) and social hierarchy-related interaction (SH-RI). To integrate these heterogeneous results into a more fine-grained and reliable characterization of the neural basis of social hierarchy, we combined coordinate-based meta-analyses with connectivity and functional decoding analyses to understand the underlying neuropsychological mechanism of SH-RL and SH-RI. We identified the anterior insula and temporoparietal junction (dominance detection), medial prefrontal cortex (information updating and computation), and intraparietal sulcus region, amygdala, and hippocampus (social hierarchy representation) as consistent activated brain regions for SH-RL, but the striatum, amygdala, and hippocampus associated with reward processing for SH-RI. Our results provide an overview of the neural architecture of the neuropsychological processes underlying how we understand, and interact within, social hierarchy.

Ranking status differentially affects rejection sensitivity in adolescence: An event-related potential study

Adolescents are sensitive to peer rejection but this may be dependent on their status. This study examined the role of ranking status on rejection sensitivity in adolescence using an experimental bargaining design. To manipulate ranking status, participants between ages 9-22-years (final sample n = 102) performed a reaction time task with two peers to induce high and low status. Next, participants played an iterative Ultimatum Game as high or low status proposer with an opposite status responder. Rejection of fair offers was associated with larger Medial Frontal Negativity (MFN) compared to acceptance of fair offers. An interaction between age and status group revealed that after rejection of fair offers, mid-adolescents showed a larger MFN when having a low status and smaller MFN when having a high status, relative to children and adults. These findings suggest that the MFN reacts as a neural alarm system to social prediction errors, signaling a need for vigilance to deviations from the norm, which is influenced by ranking status especially during mid-adolescence.

Subtle Signals of Status on Social Network Sites: Evidence From China

Social network sites (SNS) have been indispensable channels for people to access information, present themselves, and conduct commercial activities. Existing literature on online consumer behavior mainly focus on Western consumers and on explicit conspicuous signals. However, reports have shown that SNS users in China have exceeded 370 million, ranking the first in the world. Meanwhile, more and more consumers display status in more implicit ways nowadays. To fill these gaps, the present research was conducted to investigate the subtle signals of status for Chinese consumers on SNS. We proposed that frequent SNS posting leads to higher status perception among Chinese consumers. The psychological process of this effect is perceived busyness. These hypotheses received convergent support in a set of three studies. Study 1 used secondary data to preliminarily verify the positive correlation between SNS posting frequency and perceived social status. Studies 2A and 2B adopted the causal chain method to test the underlying mechanism of the effect, and to provide causal evidence for the entire relationship chain. Specifically, Study 2A examined how SNS posting frequency affects perceived busyness. Furthermore, Study 2B explored whether the differences in perceived busyness will affect social status perceptions. Implications of these findings and potential extensions in future are discussed.

Social status affects how third parties assess unfairly shared losses and unfairly shared gains

The present paper focused on how a third party's social status affects third-party intervention to maintain social fairness. Study 1 adopted a quasi-experimental design. Selecting high and low-status members of real social groups, we observed that high-status individuals intervened more forcibly and more frequently when assessing the fairness of players' behavior in a dictator game (DG). The manifestation of social status is generally divided into power and economic capital. In Study 2a, using the same DG punishment-compensation paradigm we randomly assigned the third party in the lab to high, medium, and low impact conditions, where their actions had relative multiplier effects on the resources retained by dictators and recipients. This tested whether the power to influence the situation would systematically affect third party's behavior. We found that greater influence predicted increased interventions. Study 2b investigated the influence of economic capital or intrinsic wealth on a third party's altruistic behavior by varying how much capital the third party had at their disposal to spend on punishment or recompensing. Having high capital predicted an increase in the size of penalty inflicted or compensation offered, but resource abundance had no effect on the likelihood that the third party would intervene. In conclusion, the paper showed that the social status of the third party truly does affect their altruistic interventions and the impact of social status on altruistic behaviors for maintaining fairness by the third party occurred primarily through the third parties' perception of their power. Furthermore, the influence of gain and loss contexts and social status on third-party punishment and compensation were independent of each other. This paper provided a new perspective for third-party altruistic behaviors and help to clarify the view of social fairness.

Low Competitive Status Elicits Aggression in Healthy Young Men: Behavioral and Neural Evidence

Winners are commonly assumed to compete more aggressively than losers. Here, we find overwhelming evidence for the opposite. We first demonstrate that low-ranking teams commit more fouls than they receive in top-tier soccer, ice hockey, and basketball men's leagues. We replicate this effect in the laboratory, showing that male participants deliver louder sound blasts to a rival when placed in a low-status position. Using neuroimaging, we characterize brain activity patterns that encode competitive status as well as those that facilitate status-dependent aggression in healthy young men. These analyses reveal three key findings. First, anterior hippocampus and striatum contain multivariate representations of competitive status. Second, interindividual differences in status-dependent aggression are linked with a sharper status differentiation in the striatum and with greater reactivity to status-enhancing victories in the dorsal anterior cingulate cortex. Third, activity in ventromedial, ventrolateral, and dorsolateral prefrontal cortex is associated with trial-wise increases in status-dependent aggressive behavior. Taken together, our results run counter to narratives glorifying aggression in competitive situations. Rather, we show that those in the lower ranks of skill-based hierarchies are more likely to behave aggressively and identify the potential neural basis of this phenomenon.

Neurobiological Bases of Social Networks

A social network is a web that integrates multiple levels of interindividual social relationships and has direct associations with an individual’s health and well-being. Previous research has mainly focused on how brain and social network structures (structural properties) act on each other and on how the brain supports the spread of ideas and behaviors within social networks (functional properties). The structure of the social network is correlated with activity in the amygdala, which links decoding and interpreting social signals and social values. The structure also relies on the mentalizing network, which is central to an individual’s ability to infer the mental states of others. Network functional properties depend on multilayer brain-social networks, indicating that information transmission is supported by the default mode system, the valuation system, and the mentalizing system. From the perspective of neuroendocrinology, overwhelming evidence shows that variations in oxytocin, β-endorphin and dopamine receptor genes, including oxytocin receptor (OXTR), mu opioid receptor 1 (OPRM1) and dopamine receptor 2 (DRD2), predict an individual’s social network structure, whereas oxytocin also contributes to improved transmission of emotional and behavioral information from person to person. Overall, previous studies have comprehensively revealed the effects of the brain, endocrine system, and genes on social networks. Future studies are required to determine the effects of cognitive abilities, such as memory, on social networks, the characteristics and neural mechanism of social networks in mental illness and how social networks change over time through the use of longitudinal methods.

The effect of contest participation and contest outcome on subsequent prosocial behavior

Following previous research on various aspects of contests, we aim to explore how taking part in a contest affects subsequent behavior. We focus on whether the experience of having just competed in a contest, beyond its outcome, would have an impact on other-regarding decisions towards an individual who was not part of the preliminary contest. In addition, in light of inconclusive results in the existing literature regarding the effect of contest outcome on subsequent prosociality, we reexamine this effect. In line with our hypothesis, participation in a contest was found to reduce prosociality. Additionally, we found that winning a contest reduced prosociality only when decisions were framed as "giving" decisions and not as "dividing" decisions. This finding suggests that the effect of contest outcome may depend on specific elements of the presented situations.

Upward and downward comparisons across monetary and status domains

The ability to accurately infer one's place with respect to others is crucial for social interactions. Individuals tend to evaluate their own actions and outcomes by comparing themselves to others in either an upward or downward direction. We performed two fMRI meta‐analyses on monetary (n = 39; 1,231 participants) and status (n = 23; 572 participants) social comparisons to examine how domain and the direction of comparison can modulate neural correlates of social hierarchy. Overall, both status and monetary downward comparisons activated regions associated with reward processing (striatum) while upward comparisons yielded loss‐related activity. These findings provide partial support for the common currency hypothesis in that downward and upward comparisons from both monetary and status domains resemble gains and losses, respectively. Furthermore, status upward and monetary downward comparisons revealed concordant orbitofrontal cortical activity, an area associated with evaluating the value of goals and decisions implicated in both lesion and empirical fMRI studies investigating social hierarchy. These findings may offer new insight into how people relate to individuals with higher social status and how these social comparisons deviate across monetary and social status domains.

Social Mindfulness Shown by Individuals With Higher Status Is More Pronounced in Our Brain: ERP Evidence

"Social mindfulness" refers to being thoughtful of others and considering their needs before making decisions, and can be characterized by low-cost and subtle gestures. The present study compared the behavioral and neural responses triggered by observing others' socially mindful/unmindful choices and how these responses were modulated by the social status of the agency. At the behavioral level, observing socially mindful choices made observers feel better, rate the actors as more likable, and behave more cooperatively than did observing socially unmindful choices. Analysis of event-related potentials in the brain revealed that compared with socially unmindful choices, mindful choices elicited more negative feedback-related negativity (FRN). Notably, while this effect of social mindfulness was only significant when the actor's social status was medium and high, it was undetectable when the actor's social status was low. These results demonstrate that the social mindfulness of others can be rapidly detected and processed, as reflected by FRN, even though it does not seem to receive further, more elaborate evaluation. These findings indicated that low-cost cooperative behaviors such as social mindfulness can also be detected and appreciated by our brain, which may result in better mood and more cooperative behaviors in the perceivers. Besides, the perception of social mindfulness is sensitive to important social information, such as social status.

Social hierarchies in third-party punishment: A behavioral and ERP study

Third-party punishment refers to the punishment imposed by a party whose benefit is not directly affected by any norm violations. The present study using a modified Dictator Game explored how social statuses of the involved parties modulate punishment decisions of a third-party. Systematic manipulation of the dictators' and recipients' status revealed that: higher recipient status correlated with more severe punishment, but no effect of the dictator's. We further focused on the neural underlying of this effect using ERPs. An interaction of recipient's status × fairness was observed on MFN such that only for a high-status recipient, larger amplitude was triggered by unfair offers comparing to fair offers. On LPC, the largest amplitude was observed when the offer was fair and the recipient had medium-status. These findings suggested: participants consider unfair offers proposed to high-status recipients as more norm-violating and they may evaluate the offers from the perspective of the recipient.

The Effects of Social Class on Individuals' Decision-Making Tendencies in a Prestige-Money Game: Social Value or Instrumental Value?

Through a series of three experiments, this study explored the possible influence of social class on the decision-making tendency of prestige-seeking in a Prestige-Money Game, and further explored the internal sources of such influence. In Experiment 1, the participants' social class was manipulated to examine whether there were class effects in prestige-seeking when individuals of different social classes were paired together in a Prestige-Money Game. In Experiment 2, social rank, which only contained ranking differences, was adopted as a more abstract proxy variable for social class to investigate whether class effects still existed in prestige-seeking in a Prestige-Money Game. Based on the results of Experiment 1 and 2, Experiment 3 further explored the sources of motivation for prestige-seeking among subjects of different social class. The results showed that upper-class individuals showed greater money-seeking tendencies when facing an upper-class opponent, and showed greater prestige-seeking tendencies when facing a lower-class opponent. Such tendencies were derived from social rank; instrumental value played a substantial role. The game strategy of lower-class individuals were mainly oriented toward their personal needs. Specifically, they showed greater prestige-seeking when facing an upper-class opponent, and showed greater money-seeking when facing a lower-class opponent. Such tendencies were derived from the activation of their social class identity; the role of instrumental value was limited. These findings suggest that the essential differences in the game tendencies of individuals from different social classes in a Prestige-Money Game may originate from the fact that different social classes have different demands for the instrumental value and social value of prestige.

Higher Status Honesty Is Worth More: The Effect of Social Status on Honesty Evaluation

Promises are crucial for maintaining trust in social hierarchies. It is well known that not all promises are kept; yet the effect of social status on responses to promises being kept or broken is far from understood, as are the neural processes underlying this effect. Here we manipulated participants' social status before measuring their investment behavior as Investor in iterated Trust Game (TG). Participants decided how much to invest in their partners, who acted as Trustees in TG, after being informed that their partners of higher or lower social status either promised to return half of the multiplied sum (4 × invested amount), did not promise, or had no opportunity to promise. Event-related potentials (ERPs) were recorded when the participants saw the Trustees' decisions in which the partners always returned half of the time, regardless of the experimental conditions. Trustee decisions to return or not after promising to do so were defined as honesty and dishonesty, respectively. Behaviorally, participants invested more when Trustees promised than when Trustees had no opportunity to promise, and this effect was greater for higher status than lower status Trustees. Neurally, when viewing Trustees' return decisions, participants' medial frontal negativity (MFN) responses (250-310 ms post onset) were more negative when Trustees did not return than when they did return, suggesting that not returning was an expectancy violation. P300 responses were only sensitive to higher status return feedback, and were more positive-going for higher status partner returns than for lower status partner returns, suggesting that higher status returns may have been more rewarding/motivationally significant. Importantly, only participants in low subjective socioeconomic status (SES) evidenced an increased P300 effect for higher status than lower status honesty (honesty - dishonesty), suggesting that higher status honesty was especially rewarding/motivationally significant for participants with low SES. Taken together, our results suggest that in an earlier time window, MFN encodes return valence, regardless of honesty or social status, which are addressed in a later cognitive appraisal process (P300). Our findings suggest that social status influences honesty perception at both a behavioral and neural level, and that subjective SES may modulate this effect.

Social Support Modulates Neural Responses to Unfairness in the Ultimatum Game

The current functional MRI study aimed to investigate how responders' fairness considerations and related decision-making processes were affected by social support in the ultimatum game (UG). During scanning, responders either played the standard UG with proposers (control condition) or played the modified UG in which three unknown observers showed social support for responders by acknowledging proposers' norm violation. Results revealed that participants reported higher unfairness feelings and rejection rates of unfair offers in the social support condition relative to the control condition. At the neural level, compared to the control condition, perception of social support from others induced greater activations of anterior cingulate gyrus and right anterior insula when receiving unfair (vs. fair) offers. The medial prefrontal cortex and right anterior insula were more active when the unfair offers were rejected (vs. accepted) in the social support condition than the control condition. These results highlighted the modulation effect of social support on responders' fairness considerations and related decision-making processes.

Social comparison in the brain: A coordinate-based meta-analysis of functional brain imaging studies on the downward and upward comparisons

Social comparison is ubiquitous across human societies with dramatic influence on people's well-being and decision making. Downward comparison (comparing to worse-off others) and upward comparison (comparing to better-off others) constitute two types of social comparisons that produce different neuropsychological consequences. Based on studies exploring neural signatures associated with downward and upward comparisons, the current study utilized a coordinate-based meta-analysis to provide a refinement of understanding about the underlying neural architecture of social comparison. We identified consistent involvement of the ventral striatum and ventromedial prefrontal cortex in downward comparison and consistent involvement of the anterior insula and dorsal anterior cingulate cortex in upward comparison. These findings fit well with the "common-currency" hypothesis that neural representations of social gain or loss resemble those for non-social reward or loss processing. Accordingly, we discussed our findings in the framework of general reinforcement learning (RL) hypothesis, arguing how social gain/loss induced by social comparisons could be encoded by the brain as a domain-general signal (i.e., prediction errors) serving to adjust people's decisions in social settings. Although the RL account may serve as a heuristic framework for the future research, other plausible accounts on the neuropsychological mechanism of social comparison were also acknowledged. Hum Brain Mapp 39:440-458, 2018. © 2017 Wiley Periodicals, Inc.

Brain responses to social norms: Meta-analyses of fMRI studies

Social norms have a critical role in everyday decision-making, as frequent interaction with others regulates our behavior. Neuroimaging studies show that social-based and fairness-related decision-making activates an inconsistent set of areas, which sometimes includes the anterior insula, anterior cingulate cortex, and others lateral prefrontal cortices. Social-based decision-making is complex and variability in findings may be driven by socio-cognitive activities related to social norms. To distinguish among social-cognitive activities related to social norms, we identified 36 eligible articles in the functional magnetic resonance imaging (fMRI) literature, which we separate into two categories (a) social norm representation and (b) norm violations. The majority of original articles (>60%) used tasks associated with fairness norms and decision-making, such as ultimatum game, dictator game, or prisoner's dilemma; the rest used tasks associated to violation of moral norms, such as scenarios and sentences of moral depravity ratings. Using quantitative meta-analyses, we report common and distinct brain areas that show concordance as a function of category. Specifically, concordance in ventromedial prefrontal regions is distinct to social norm representation processing, whereas concordance in right insula, dorsolateral prefrontal, and dorsal cingulate cortices is distinct to norm violation processing. We propose a neurocognitive model of social norms for healthy adults, which could help guide future research in social norm compliance and mechanisms of its enforcement.

Gender Differences in Behavioral and Neural Responses to Unfairness Under Social Pressure

Numerous studies have revealed the key role of social pressure on individuals' decision-making processes. However, the impact of social pressure on unfairness-related decision-making processes remains unclear. In the present study, we investigated how social pressure modulated men's and women's responses in an ultimatum game. Twenty women and eighteen men played the ultimatum game as responders in the scanner, where fair and unfair offers were tendered by proposers acting alone (low pressure) or by proposers endorsed by three supporters (high pressure). Results showed that men rejected more, whereas women accepted more unfair offers in the high versus low pressure context. Neurally, pregenual anterior cingulate cortex activation in women positively predicted their acceptance rate difference between contexts. In men, stronger right anterior insula activation and increased connectivity between right anterior insula and dorsal anterior cingulate cortex were observed when they receiving unfair offers in the high than low pressure context. Furthermore, more bilateral anterior insula and left dorsolateral prefrontal cortex activations were found when men rejected (relative to accepted) unfair offers in the high than low pressure context. These findings highlighted gender differences in the modulation of behavioral and neural responses to unfairness by social pressure.

The role of social status and testosterone in human conspicuous consumption

Conspicuous consumption refers to the phenomenon where individuals purchase goods for signalling social status, rather than for its inherent functional value. This study (n = 166 male participants) investigated how the outcome of a social competition influenced conspicuous consumption, and its association with competition-induced testosterone reactivity. Winning a competition increased both explicit and implicit preferences for higher-status vs. lower-status products, using both natural stimuli (prestigious cars) and laboratory-tagged stimuli of matched value (university T-shirts). Competition also influenced behaviour in an Ultimatum Game, such that winners were more likely to reject unfair offers. Competition outcomes had no discernible influence upon salivary testosterone levels, and neither basal testosterone levels nor testosterone reactivity induced by competition predicted the conspicuous consumption measures. Our data indicate that winning a competition lead to more dominant behaviour, albeit in a manner that is not statistically regulated by testosterone, possibly through increased feeling of entitlement.

Neural substrates of context- and person-dependent altruistic punishment

Human altruistic behaviors are heterogeneous across both contexts and people, whereas the neural signatures underlying the heterogeneity remain to be elucidated. To address this issue, we examined the neural signatures underlying the context- and person-dependent altruistic punishment, conjoining event-related fMRI with both task-based and resting-state functional connectivity (RSFC). Acting as an impartial third party, participants decided how to punish norm violators either alone or in the presence of putative others. We found that the presence of others decreased altruistic punishment due to diffusion of responsibility. Those behavioral effects paralleled altered neural responses in the dorsal anterior cingulate cortex (dACC) and putamen. Further, we identified modulation of responsibility diffusion on task-based functional connectivity of dACC with the brain regions implicated in reward processing (i.e., posterior cingulate cortex and amygdala/orbital frontal cortex). Finally, the RSFC results revealed that (i) increased intrinsic connectivity strengths of the putamen with temporoparietal junction and dorsolateral PFC were associated with attenuated responsibility diffusion in altruistic punishment and (ii) increased putamen-dorsomedial PFC connectivity strengths were associated with reduced responsibility diffusion in self-reported responsibility. Taken together, our findings elucidate the context- and person-dependent altruistic behaviors as well as associated neural substrates and thus provide a potential neurocognitive mechanism of heterogeneous human altruistic behaviors. Hum Brain Mapp 38:5535-5550, 2017. © 2017 Wiley Periodicals, Inc.

Proposers' Economic Status Affects Behavioral and Neural Responses to Unfairness

Economic status played an important role in the modulation of economic decision making. The present fMRI study aimed at investigating how economic status modulated behavioral and neural responses to unfairness in a modified Ultimatum Game (UG). During scanning, participants played as responders in the UG, and they were informed of the economic status of proposers before receiving offers. At the behavioral level, higher rejection rates and lower fairness ratings were revealed when proposers were in high economic status than in low economic status. Besides, the most time-consuming decisions tended to occur at lower unfairness level when the proposers were in high (relative to low) economic status. At the neural level, stronger activation of left thalamus was revealed when fair offers were proposed by proposers in high rather than in low economic status. Greater activation of right medial prefrontal cortex was revealed during acceptance to unfair offers in high economic status condition rather than in low economic status condition. Taken together, these findings shed light on the significance of proposers’ economic status in responders’ social decision making in UG.

Pulling Rank: Military Rank Affects Hormone Levels and Fairness in an Allocation Experiment

Status within social hierarchies has great effects on the lives of socially organized mammals. Its effects on human behavior and related physiology, however, is relatively little studied. The present study investigated the impact of military rank on fairness and behavior in relation to salivary cortisol (C) and testosterone (T) levels in male soldiers. For this purpose 180 members of the Austrian Armed Forces belonging to two distinct rank groups participated in two variations of a computer-based guard duty allocation experiment. The rank groups were (1) warrant officers (high rank, HR) and (2) enlisted men (low rank, LR). One soldier from each rank group participated in every experiment. At the beginning of the experiment, one participant was assigned to start standing guard and the other participant at rest. The participant who started at rest could choose if and when to relieve his fellow soldier and therefore had control over the experiment. In order to trigger perception of unfair behavior, an additional experiment was conducted which was manipulated by the experimenter. In the manipulated version both soldiers started in the standing guard position and were never relieved, believing that their opponent was at rest, not relieving them. Our aim was to test whether unfair behavior causes a physiological reaction. Saliva samples for hormone analysis were collected at regular intervals throughout the experiment. We found that in the un-manipulated setup high-ranking soldiers spent less time standing guard than lower ranking individuals. Rank was a significant predictor for C but not for T levels during the experiment. C levels in the HR group were higher than in the LR group. C levels were also elevated in the manipulated experiment compared to the un-manipulated experiment, especially in LR. We assume that the elevated C levels in HR were caused by HR feeling their status challenged by the situation of having to negotiate with an individual of lower military rank. This would be in line with the observation that unequally shared duty favored HR in most cases. We conclude that social status, in the form of military rank affects fairness behavior in social interaction and endocrine levels.

When Do Low Status Individuals Accept Less? The Interaction between Self- and Other-Status during Resource Distribution

In real-world social interactions, social status influences responses to resource distribution. However, the way in which one’s own social status interacts with another’s status to influence responses to resource distribution is far from clear. In the current study, we dynamically manipulated participants’ social status and then asked participants to act as recipients in the ultimatum game (UG) along with proposers whose social status was made known to the participants. Experiment 1 used a between-participants design in which the participants were assigned as being of either high or low status according to their performance in a math competition (i.e., rank-inducing task). In Experiment 2, social status was manipulated within-subjects using the same rank-inducing task, with rounds of UG interleaved between rank-inducing sessions. Findings from the two experiments showed that both self-status and other-status influenced responses to UG offers, as participants were more likely to accept low offers from high status than low status proposers; this effect was particularly robust for low status participants when compared with high status participants. These findings suggest that, in comparison with individuals in high status, individuals in low status are more willing to accept low offers during resource distribution and are more affected by other-status considerations.

Diffusion of responsibility attenuates altruistic punishment: A functional magnetic resonance imaging effective connectivity study

Humans altruistically punish violators of social norms to enforce cooperation and pro-social behaviors. However, such altruistic behaviors diminish when others are present, due to a diffusion of responsibility. We investigated the neural signatures underlying the modulations of diffusion of responsibility on altruistic punishment, conjoining a third-party punishment task with event-related functional magnetic resonance imaging and multivariate Granger causality mapping. In our study, participants acted as impartial third-party decision-makers and decided how to punish norm violations under two different social contexts: alone (i.e., full responsibility) or in the presence of putative other third-party decision makers (i.e., diffused responsibility). Our behavioral results demonstrated that the diffusion of responsibility served as a mediator of context-dependent punishment. In the presence of putative others, participants who felt less responsible also punished less severely in response to norm violations. Our neural results revealed that underlying this behavioral effect was a network of interconnected brain regions. For unfair relative to fair splits, the presence of others led to attenuated responses in brain regions implicated in signaling norm violations (e.g., AI) and to increased responses in brain regions implicated in calculating values of norm violations (e.g., vmPFC, precuneus) and mentalizing about others (dmPFC). The dmPFC acted as the driver of the punishment network, modulating target regions, such as AI, vmPFC, and precuneus, to adjust altruistic punishment behavior. Our results uncovered the neural basis of the influence of diffusion of responsibility on altruistic punishment and highlighted the role of the mentalizing network in this important phenomenon. Hum Brain Mapp 37:663-677, 2016. © 2015 Wiley Periodicals, Inc.

Social hierarchy modulates neural responses of empathy for pain

Recent evidence indicates that empathic responses to others' pain are modulated by various situational and individual factors. However, few studies have examined how empathy and underlying brain functions are modulated by social hierarchies, which permeate human society with an enormous impact on social behavior and cognition. In this study, social hierarchies were established based on incidental skill in a perceptual task in which all participants were mediumly ranked. Afterwards, participants were scanned with functional magnetic resonance imaging while watching inferior-status or superior-status targets receiving painful or non-painful stimulation. The results revealed that painful stimulation applied to inferior-status targets induced higher activations in the anterior insula (AI) and anterior medial cingulate cortex (aMCC), whereas these empathic brain activations were significantly attenuated in response to superior-status targets' pain. Further, this neural empathic bias to inferior-status targets was accompanied by stronger functional couplings of AI with brain regions important in emotional processing (i.e. thalamus) and cognitive control (i.e. middle frontal gyrus). Our findings indicate that emotional sharing with others' pain is shaped by relative positions in a social hierarchy such that underlying empathic neural responses are biased toward inferior-status compared with superior-status individuals.